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1BB deserves a medal for this thread.  This needs to stay in the active threads and not go to the archive.

ETA:  Feral informed me that this is already marked "No Archive".

CRAP!!!  I just spent the last three hours typing a detailed semi intelligent reply and the board/laptop/net ate it....    ARRGH!!!

Sorry for the following brevity, but I'm rapidly running out of time!



I'll have to find the right land first, but definitely within the next 1-2 years.––  As soon as possible.



That stinks!!!  I didn't want to put more than 80k into the shell itself if at all possible.  I may have to budget more then.  Long story (not worth retyping), but I may have much more money by build time.  I can't count bucks that aren't in the account yet though, so I'm trying to keep it reasonable.  If I overextended myself I might end up building someone elses dome.LOL  


I'd be more than happy to round up a bunch of steaks!!!LOL

I would love to have you help me!  Who better than someone who actually gives a crap, and knows what I want better than I do!  I'd still have to pay you though.  I don't know jack about shotcreting, foam spraying, ect.  I'd just be an unskilled but anxious laborer!  I'm usually chained to my work, but I'd take annual leave for the duration of the job and I'd stay on site and work my butt off until the dome was up and the shell was finished!

If I were going to get a quote from my local plant(s), about how many yards of what recipe of concrete would we need?  I know it'd cost more, but if it wasn't too much more and helped out by expediting the build...

Also:  How wide of a hole would be best for a 40' diameter dome?  If I dug out 60' diameter would that be suffecient?  It'll depend on the lay at the site, but if it's flat I'd doze a long ramp in, and if it's sloping I'd cut a channel straight out and down the face of the outer slope.

How long would it be before I could backfill against the walls?  Sand or pea gravel best?  It'd be a pain, but I'd probably use the front bucket on the hoe to fill it in myself.  The last time I let someone backfill a wall for me they cracked it in two places by constantly running into it.




I love your way of thinking, but I'm not sure I can afford all of it together.  I won't know until I get the property, once that time comes it's go time for me.  Hopefully I'll have good news by then and can afford the 12KW set and the rest also.  If not I'll have to budget much less shelter appliance-wise.


I'm guessing that wouldn't add too much to the shell cost?


All good ideas, but if I can't afford it and end up with access to NG, then I'd likely punt and go with a smaller NG converted genset instead.  I'd could scrape by with much less if necessary.  Your way would definitely be nice though!  I need to look at the air thing more too. I was originally thinking of a central vertical shaft of some sort taht would carry air ducting in and out for the central air, etc.  It could carry an exhaust pipe up and out o fthe dome along with an intake if necessary, I'd just need to keep the exhaust well clear of wherever the shelter air ended up coming from.


If I had the windows steel shuttered and locked from within, it'd still probably work as the shutter gaps around the window would probably flow enough air.


I'd have no qualms at all with diesel inside.  I have used diesel equipment for years, have diesel truck, etc.  It's a very safe fuel, and you'd almost have to try really hard to screw it up.


Good idea.  I'd want the toilets seperate anyway.  The asshats that built the house I own now botched the drain field.  I had to dig (my uncle's hoe) a sump at the end of the drain field where it popped up and put in twenty tons of riprap to fix the problem.  In the interim I had seperated out most of the non-toilet drains and it lightened up the load on the field considerably.  


Thank you!  That's very useful info!  I need to read more about the different filter systems.  I'm thinking ANDAIR/LUWA, but I'm not set on one yet.  Fallout is my primary concern.


I could make or have fabbed a tank like that easily.  Stainless is pricey, but if it's worth doing...


I currently have two portable disposals (in my avatar-LOL), but that is a good idea also.


Yes, excellent sense!


Yes I am curious about how to pour the floors.


Thank you very much for all of this extremely useful information!!!  You have given me enough info to make my brain explode, and I'm going to have to tackle it like an extra large pizza–– one bite at a time!LOL
I had written a much better reply, but I guess I'll learn to cut and paste it from word or something next time.LOL

Do you  have any exterior pics?

JimBeam, I don't want to take up time and space  here for pictures of the outside when you can go right to Monolithic's site and see more pictures than you could ever imagine. It isn't that I don't want to take the time to answer you, it just comes down to time, mine , and use of space. I will say this, if you can dream it up, I am 99% sure it can be done.

Variable556, I have done the samething, but only once. Now when I have a longer post, I copy and paste it into an email and send it to myself in the event something happens. I may do this three or four times for one post. I hate doing things twice.

Okay, I see your time frame now. I was thinking you are doing something in the spring. From the sound of it, you are more than likely looking at 2011 or 2012? Either way, if I can help you out, I will. I'm not worried about getting paid. Seriously, I don't need the money, but if you really feel the need to pay, I would like to see you make a donation to a local charity(s) of your choice in the amount of your choice. Do what you feel is right.


Anyway, I have put a little thought into your shelter's overhead cover just to give you an idea what it will take. An engineer will need to run the numbers to make sure, and to get it stamped.

I think 14'' of concrete along with another 6'' of concrete in the dome shell and another floor between you, should give you pretty good protection factor in just about any situation you find yourself. Now we just need to figure out how to hold up 88 tons of wet concrete and 3 tons of rebar. The best way to build this is in two pours, and I will explain them as we go.

I ran some quick numbers to get an idea what we are up against. Using some know factors about the dome shell, I don't think it will be to hard to do at all, or that expensive really. The shell can support 2000 pounds or one ton per square foot. That is an engineering fact, and it can do more than that.


Read this article and pay close attention to paragraph four. This will give you an idea as to its strength.

http://www.monolithic.com/stories/iraq-mosque

And another good article.

http://www.monolithic.com/stories/testament-to-domes-strength


Below is the picture I drew. It isn't great, but you get the idea. It is a cut away side view of the dome shell and concrete floor. Basically the floor will weigh in at about 180,000 pounds. Adding in our safety factor of 7 times, that comes out to 1,260,000 pounds or 630 tons that when completed we need to be able to support. For now, all we need to support is about 100 tons.

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To do this, we will use steel trusses that are two feet OC. Then we will lay in a grid of #6 rebar (3/4''), 1' OC that is 75 grade. That means that rebar will hold 75,000 psi if it were one inch square, and it isn't. This rebar has a cross section of 44% of one square inch, so this rebar can only hold 44% of 75,000 pounds or 33,000 pounds per stick. Make sense?

Basic idea of a truss layout. Again, an engineer will lay it out according to the trusses he wants to use. I will say we did a 4'' floor on a 55 foot dome and they had the trusses 4' OC. I called to make sure there wasn't a mistake as I couldn't believe they would hold up and he said it was correct. I watched the steel workers do their thing with the trusses and the concrete boys doing theirs, and I will tell you this, my pucker factor was maxed out. You couldn't pound a pin up my ass with a jackhammer. It wasn't a total free span of 55' but I really didn't think there was enough under it to hold it up.

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Now without trying to explain everything, I will just say that a 40' dome with rebar every foot OC, you will have a grid like in the picture below. I didn't finish it off completely, because you get the idea. Anyway, the rebar will be 50' long for the longest runs and there are no breaks or splices in the rebar anywhere. I say 50' long, because it has to go into the dome shell 5' on each side of its run. It has to go that far so we are spreading the max full load over a larger area of the dome.

Remember, the shell can support 2000 per square foot. If we have one foot of truss, and five feet of rebar going up into the shell, we have 6 total feet of area we are spreading the max full load out on to. Now the dome is 125.6 feet around, times 6 feet of truss and rebar, and we have 753.6 area feet to spread the weight out over. Also, the rebar is tied into the verticals in the shell running from the footing to the very top of the dome. So really, you are spreading this weight out over the entire dome.

The dome shell can support 2000 pounds per square foot, multiply that times 753.6 square feet that our #6 rebar and truss are using, and that equals 1,507,200 pounds we can support, and we only need 1,260,000 with our safety factor.


Here is a good article about a family who hung over 250 tons from their dome shell. Read the very last two paragraphs.

http://www.monolithic.com/stories/the-eye-of-the-storm


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Now when building this, we are not going to pour 14'' of concrete all at once. We will pour 4'' to 6'' to cover the rebar pretty good, and let it set up. Then come back in a few days and pour the rest. What happens is our trusses are supporting the lighter load of 4'' of concrete in the first pour, and once it sets up, our rebar and dome shell now supports the rest of the pour. We can spray a bonding agent on the first pour so when our next 10'' or 8'' of concrete is poured, it acts as one pour.

Now for the cost of this. I am not sure what trusses go for, but you will have about 700 feet of them using my numbers and again, it depends on what an engineer says, but I am gining you an idea what it will be. If they run you $5 a foot, you are looking at $3500. Concrete, you will have about 55 yards @ $100 a yard, $5500. Rebar, you will have about 4500 feet or so. It is a top grade rebar and VERY heavy at 1.502 pounds per foot. I am figuring it will be close to $0.50 a foot, so another $2250. Steel sheeting, This is to lay across the truss to pour concrete onto. I am not sure what it is going for, but if we use a figure of two pounds of steel psf for the steel sheeting, and we use about 1400 sf after all is said and done, and it goes for $0.50 a pound, we are looking at $1400.

Misc............$5,000 Truss anchors and whatever's
Truss............$3,500 ???
Concrete......$5,500 55 yards @ $100 yd
Rebar...........$2,250
Steel.............$1,400 This is to lay across the truss to pour onto. I am not sure what it is going for, but sheet @ 2 lbs psf @ $0.50 a pound is
                                    what I figured.
Total cost.......................................................................$16,250


Now, if you want to think in a completely different direction, you could do this, build a seperate underground dome altogether. Build a 32' dome that is 18' tall with a 6' stem wall, and you have the following.

The dome will have 2350 square feet over the shell, and 804 sf of living area on the first floor, and 603 sf useable on the second floor for a total of 1407 total sf of real useable living area.

The cost is:

Air form................$6,500
Floor.....................$2,500
Foam....................$4,000
Rebar...................$2,800
Shotcrete.............$3,000
Misc.....................$3,000
Total.................................$21,800

Now here is the best part. It will cost you $10,490 just to build the SHELL section for your shelter in your 40' dome. Add in the cost of your over head cover of $16,250 and we have a total $26,740. If we just build a whole new dome, we save almost $5000 and get an extra 149 sf of living area. You would also have 14,476 CF inside your shelter with at least 11,476 useable air which is a huge increase over what you had in the 40' dome shelter.

Not only that, you put this 4 feet underground along with the concrete dome shell and you have the highest protection factor possible without doing a thing special to the domes. Build this small dome first, then back fill, and start on the larger dome.

You would have to build a small connecting tunnel from dome to dome, but that is going to be less than $2000 and will be built just like both domes, foam, rebar, and concrete and all three will be connected as one. The only difference is will be when you enter the shelter, you will be on the second floor of the shelter and walk down some stairs to get to the first floor.

It would look something like this. I scaled it to your original drawing so it is as accurate.

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Yeah, I'm learning!LOL


Correct, I'm trying hard to find "the place", but I haven't found it yet.  Doing something like this will be monumental for me and I need to get the right spot to make it all click.  Thank you tremendously for offering to help if you can, I owe you already just for the tons of good info!!!  You are definitely a class act Sir!!!  



I had read the first one, but I hadn't seen the second one.  Hopefully a GBU-28 will never knock on my roof!LOL  It is also good to know it'd likely be 2.75" resistant...

I won't know until later whether I can afford all of that floor thickness-wise.  I was originally just thinking a regular 4"-6" thick floor.  I hadn't considered doing it that thick.LOL  I know that is how it's supposed to be done, but I was trying to cheat with the deep well hidey hole approach.  I hadn't run it past a shelter pro though.  My protection concerns were for primarily fallout, and I was hoping that the distance below the shell surface (combined with the inverse square law for radiation) would cover my bases close enough.  Your way would be ideal, but I won't know if I'd have enough funds for something like that until closer to launch date.


Yes you actually explain things well so i can figure them out.  Thank you!


I would have ran!LOL


That just blows my mind!  I know they are very strong, and I believe the math, it is just so hard for me to conceive of them actually being that strong!LOL  I believe you 100%, it just makes you shake your head trying to wrap your brain around it.  That is more weight than a complete solid rocket booster from the Shuttle!!!  Almost enough for the external tank instead!!!  Egads!!!



I showed the wife that one too.  It's really neat.




I like the idea, but still I'd have to see if I could conceivably swing that.  I have to admit, I'd feel a lot cockier with 14" of concrete overhead...  Thank you very much for explaining all of that.  I thought the floor would need jacks instead.  These domes are amazing.  


Now here is where you start to become dangerous!  Your mind should be registered as a "Destructive Device" with the NFA registry as being potentially injurious to my budget and mental health for possibly not being able to afford something like that!!!

That is a great idea, and would be truly awesome.  One possible problem I would see is whether I could get to that depth.  I would just have to dig and see.  The larger footprint would increase my odds of finding really hard stuff, but I'd just have to give it a go and find out.  I'll have to plan for less at this point, but if i could afford it come "go time", I'd sure like something like that.  I think the wife might need some meds along the way though, if we did go that route...  She is still in shock over the 14" floor.    



ETA:  The wife thinks I'm a little crazy, but after reading this thread she likes the dome better....  I'll keep working on her!

1_BIG_BUNKER, thank you for taking the time to post here. I've been following all your threads with great interest.

You mentioned 6" for wall thickness. We are going to have to deal with a retaining wall issue at some point, and I had originally planned to put in an 8-12' diameter corrugated piping for a shelter and running a tunnel into our basement when we have the retaining wall repared. However, the appeal of concrete is the additional protection factor it affords as I'm not certain how deep I can go before I hit bedrock. Of course, thicker concrete would also offer better blast protection as well. So, I was wondering how thick the dome walls can be made? When do you have to add extra layers of rebar?

As mentioned by many,  Thanks for all the Great info.  How thick does the slab and footer need to be to support these domes?
Lets say you have a 50" dome with 10" wall.  What would the concrete slab specs be?
and Happy Thanksgiving a day early

No problem. I enjoy it. I REALLY LOVE building bunkers, and helping others build them as well. I kind of feel like a kid again who has a fort if you will.

The domes do not need a slab at all. If you never wanted to put a floor in one and leave it as a barn for live stock, that's fine. The slab is for people only and has nothing to do with supporting the shell.

You see, what keeps the dome up, is the rebar in the footing which is called a ring beam. To explain it better, it is like taking a plastic bowl and turning it over and then applying weight to it. It wants to spread out and go flat. Now if you wrap a big hose clamp around the base of that plastic bowl, it gives it the support it needs to stay up. The hose clamp holds the base from spreading out. The rebar ring beam does the samething in a dome as a hose clamp does on a plastic bowl turned upside down. Make sense?

Another thing is multiple domes. When you see several domes together the rebar in the floor does NOT look like the dome shells do with big open arches. We still HAVE to have COMPLETE ring beams in the floor to hold up each dome even though the shells have big open arches. Basically what the floor looks like before concrete is poured, is something like the Olympic rings. They are all complete rings with no breaks in it. Now above the arch in the dome shell, you do have to make another ring beam with rebar to create what's called a concrete beam.  What you do above ground you HAVE to do below ground so the weight is carried evenly around the break in the shell be it a doorway, garage door, or arch inside the dome. Does that make sense? It is easier to see and do than explain.

So, you see, a floor really has nothing to do with it at all.  I pour a floor along with the footing because it is easier to do without a dome over your head. I also pour a floor 6'' thick. Mainly because we staple 1/2'' pex tubing for in floor heat, to foam we spray on the ground. I don't know anyone who will hammerdrill down that far to hit the tubing when doing walls. Plus it seems the home owners always move a wall somewhere and it gives us a little room to work with if need be, and the wall they want to move is a load bearing wall. In areas where there is no need for floor heat, I put in a 4'' floor unless there are several floors then I stay with a 6'' slab. People never stick with their blue prints and that's fine, I plan for it. I mean people want to build their dream and who am I to turn it into a nightmare because they want to move a wall. I do what makes them happy.

The other reason I pour the floor and footings at the same time is because of the inflator fan. You see, when we inflate a dome airform, we are inflating with 1/13th of a psi. Yes, that sounds like very very little pressure, but if you apply the math, it is a lot. That equals just over 11 pounds of lift per square foot of airform material. So take the above dome that has 4776 square feet over the shell, I believe, multiply that times 11 pounds and you now have 52,536 pounds or 26.268 tons of lift.

Now if we just have a footing in there, and it is 1.5'x1.5' or 2.25 square feet, and it is all the way around the 40' dome, we have 125.6 feet around, times 2.25 square feet we have 282.6 total cubic feet. Divide that by 27 cubic feet for one yard of concrete and you have 10.5 yards of concrete in our footings. Concrete is about 3200 pounds per yard, so we have 33,600 pounds trying to hold down over 52,000 pounds of lift in the airform. It just doesn't work. So I up it to 2'x2' and pour a floor. The extra room in the footing gives us room to work, and added weight IF the owner for some reason does not want everything poured at once and changes his mind. It has happened. We can not just move the forms out so there is more concrete because then we would have a 41 or 42 foot dome and the airform won't fit. Try digging out the inside AFTER 1.5'' of foam is sprayed on the ground. It is just easier to plan ahead from the start.

Now if I have just the footings in there, the air will push against the ground and airform and it can lift the concrete footings right off the ground and burp the air pressure. It will keep doing this until the weight of the shell is more than the up lifting force. You can't build that way. So unless the owner really doesn't want to do a single pour of footing and floor, I pour both at the sametime. Now the airform is lifting against one solid mass that is all connected together with rebar. Nothing is going anywhere.

The only thing I do when I pour it all in one, is I seal the concrete floor. That way when foam is sprayed in the dome, it will not stick to the floor if the plastic that's laid down happens to move, and neither will any shotcrete for that matter. Makes for easy clean up, but it has to be striped before any staining or anything like that can be done to the floor. It is an extra couple steps, but man that foam will NOT come of a floor that is not sealed. I mean that. Even floor grinders won't take it off. Foam is FOREVER on an unsealed floor. Just becareful not to get any sealer in the mechanical lock in the footing as you want everything to stick there.

The footings are almost all the same for any dome up to 60'. After that, they change. I always put in a 2'x2' footing unless it is going underground then I increase it to 2.5'x2'

Onething people always ask is man those must be very heavy, and with no floor, they have to sink. Actually, the weight per square foot is not that much. Lets use the following numbers.

Airform....................................2000 pounds
Concrete shell and footing.....220,000 pounds, no floor only footings
Rebar.....................................15,000 pounds
Foam.......................................6000 pounds
Total..................................................................243,000 pounds or 121.5 tons

We have a 2' wide footing for 125.6 feet, so we have 251.6 square feet to spread this weight out on. That comes to 966 pounds per square foot on the soil. Now add in a floor to spread the weight even more and you can quickly see how you can easily build a dome on just about any soil and most are running at least 1500 pound soil. The domes foot print is very light when you do the math which is very important in earthquake areas when you have to take into account the soil and liquefaction.





The dome walls can be made as thick as you want. Once you get past a certain point, you do have to add in another layer of rebar, but then again that is when you are talking about walls that are over 12'' thick. Like bigger domes, around 100 foot across or so will have concrete walls 18'' at the base and an extra layer of rebar running up for maybe 15-20 feet. Don't worry about extra rebar or anything like that with anything that would be built for a family unless it is a shelter. I mean we can, and it is VERY easy to do, but I think what you gain out of it in strength and protection is not worth the cost if you can go underground. I mean going down underground and having 4 feet of earth over you is great protection and you don't have to do anything special to the shell to do this. I would not worry about adding in anything extra until you started to get past 10 feet or so underground at the top of the dome. If you wanted to do 12'' walls, just double the shotcrete and rebar cost and you will be fine.

Again, the shell can take 2000 pounds per square foot. For ease of numbers, let's say soil is about 100 pounds per cubic foot, so if you have one square foot of soil 20 feet high, you have 2000 pounds. That means I wouldn't worry at all until I got to about 10' underground. Then I would start to worry about safety factors, wet soil, vehicles parking on it or driving over it, and what not.



Below is the first school built and before they would let anyone in it, Dave told me they made them put 1,000,000 pounds of weight on top of the school in the form of silo staves, before they would allow construction to start on the inside. He said it took them almost a month to get them all up there on the top of the dome and another month to take them down. Dave told me he wishes they would have taken a more accurate measurement after they did the test, because using a simple tape measure showed no movement at all in the dome shell. He said we should have measured to the thousandth of an inch, but we didn't think about it at the time. He also said that most of the weight was at the top because the curve of the dome made it so that the staves would slide off at a certain point, but they were running around 2000 per square foot or more.

Something else that is interesting is towards the bottom. Read about the utiliy costs. They are saving a huge amount over their SMALLER conventional built school. Here is some of what they said.

''The domes provide in excess of 110,00 square feet of enclosure, while Sweet/Montour measures in at about 27,000 square feet. During the 1995-96 school year, power at Sweet/Montour totaled just under $9,000; during the same period, the high school power consumption came to $10,100. [Ed. Note: That is 33.3 cents per square foot for the elementary school versus 9.2 cents per square foot in the dome.]''

http://www.monolithic.com/stories/feature-school-emmett-highschool

Something else you might want to consider is covering the outside to give you added protection and protect the airform as well.

http://www.monolithic.com/stories/cover-dome-with-tile-or-rock/photos/9

http://www.monolithic.com/stories/cover-dome-with-tile-or-rock/photos/8

Here is some better pictures of a couple domes both inside and out. You can see close up what the rock coverings look like.

Pictures

Article


And another one you might enjoy reading about.

Pictures

Article

I've been interested in this also.  More info at:

http://www.monolithic.com/topics/homes

WOW! Antelope Springs Ranch is AMAZING!!!!!



All the work you've done is outstanding.



I have land in WI I'd love to build one of these on in about two years. Maybe I'll look you up.



Thanks for some outstanding posts!

Originally Posted By Gerri:
1_BIG_BUNKER, thank you for taking the time to post here. I've been following all your threads with great interest.

You mentioned 6" for wall thickness. We are going to have to deal with a retaining wall issue at some point, and I had originally planned to put in an 8-12' diameter corrugated piping for a shelter and running a tunnel into our basement when we have the retaining wall repared. However, the appeal of concrete is the additional protection factor it affords as I'm not certain how deep I can go before I hit bedrock. Of course, thicker concrete would also offer better blast protection as well. So, I was wondering how thick the dome walls can be made? When do you have to add extra layers of rebar?


Originally posted by 1_BIG_BUNKER:
The dome walls can be made as thick as you want. Once you get past a certain point, you do have to add in another layer of rebar, but then again that is when you are talking about walls that are over 12'' thick. Like bigger domes, around 100 foot across or so will have concrete walls 18'' at the base and an extra layer of rebar running up for maybe 15-20 feet. Don't worry about extra rebar or anything like that with anything that would be built for a family unless it is a shelter. I mean we can, and it is VERY easy to do, but I think what you gain out of it in strength and protection is not worth the cost if you can go underground. I mean going down underground and having 4 feet of earth over you is great protection and you don't have to do anything special to the shell to do this. I would not worry about adding in anything extra until you started to get past 10 feet or so underground at the top of the dome. If you wanted to do 12'' walls, just double the shotcrete and rebar cost and you will be fine.

Again, the shell can take 2000 pounds per square foot. For ease of numbers, let's say soil is about 100 pounds per cubic foot, so if you have one square foot of soil 20 feet high, you have 2000 pounds. That means I wouldn't worry at all until I got to about 10' underground. Then I would start to worry about safety factors, wet soil, vehicles parking on it or driving over it, and what not.



I would really like to have the entire thing 10' underground measured from the top of the dome. The problem is I'll likely have to deal with bedrock. In addition, there is a great deal of clay in the soil here. So, my understanding is, when it gets wet, it puts a great deal of force on foundations and basements. I really don't know if building it thicker will be needed, or will be adequate.

I have thoroughly enjoyed reading this thread so far.  

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Holy shit!

I saw these homes years ago, but I forgot completely about them ...

If I ever build a home, it will be a monolithic dome.  Incredible.

Hey 1BB,

Can you tell me a little more about the foam you use.  You mentioned that you spray 1 to 2 inches of 2.7lb foam on the airform and also the ground under the slab.  

What is a good source and price for the foam you buy?

What are the disadvantages of using a lighter foam like 2lb or 1.8lb?

Are there types of foam to avoid?  

Also, do you think foam and shotcrete could be sprayed to the underside of a conventional flat steel roof that has been installed on steel trusses to give thermal mass to the roof of a non dome house?

You mentioned that you mix your shotcrete yourself, how much time can pass between batches before you would have problems with the concrete having distinct seams from different batches in it?  It would seem that you would have to be mixing the batches up pretty fast. What type of concrete mix do you make for the domes? Typical 1-2-3 (1 part cement -2 parts sand -3 parts agregate) mix?

thanks

I know you said you didn't want two separate structures, but could something like this work?







I'm just thinking that w/ two separate structures, you wouldn't have to go deeper than your basement, and you might even be able to get rid of the stem wall and go "all dome"...



(was I smoking something, or did I remember 1BB saying it was cheaper to do a dome than a dome + stem wall?)



Why would you not want to build another level below the basement?  One thing I'm thinking of is your plumbing... how deep is that septic tank, and keeping everything flowing downhill... sure, there are pumps, but I don't know that I'd want to rely on one in a fallout situation.



Just some thoughts.



 

We spray foam in basically two layers. Each is 1.5'' thick.

The blueprints call for 2 pound foam, but I use 2.7 pound foam. All that means is one cubic foot weighs whatever the rating of the foam is. Also, keep in mind that the higher the pound rating of foam the less coverage you get per set. So a 2 lbs. foam will cover about 3200 board feet and 2.7 is about 2500 BF. The foam is heavier and a lot stronger the higher the rating, but you lose coverage and it costs more to do your project.

You do not gain any insulation value with the higher ratings. It is basically the same when you spray three inches thick. I use the higher rating, because of a few reasons. One, if the power goes out, and my inflator fans shut off, there is a chance the dome could sag or even come down if I do not have the whole shell covered in foam. With the heavier, stronger foam, there is very very little chance this could happen.

To give you an idea how strong the foam is, I was building a 50' dome that was 24' tall and all I had done was the foam and rebar in it. That morning we were going to start spraying shotcrete when the weather turned. There was an F3 come through, took out the power, my inflator fan, and airlock to get in and out of the dome. The farm next to us was gone. Just a silo, and a chimney was left standing. Winds were around 175mph. We needed a new fan, and fixed the airlock, and within three or four hours we were ready to spray shotcrete, but still had no power. The curve of the dome along with just foam and rebar was more than strong enough to easily survive an F3.

The other reason I use 2.7 foam is for hail. At some point every home gets hit with hail. When it hits a dome, it will make small dents in the shell. Remember, it is airform, foam, then shotcrete on the inside. With the heaver foam, those small dents pop back out in a short time. The longest I seen was about two months but that was pretty good size hail running 2-3'' in size. With the 2 pound foam you will take longer with bigger hail. You can't see it unless you get up next to the shell and look up the shell. Then you can see it, but not looking at it head on.

For a dome you have to use at least 2lbs foam. For a conventional home, I wouldn't use less than 1.25lbs foam. The reason is, once you start getting lighter than that, it's more of a sound deadening foam than it is insulating. The lighter the foam, the more coverage you get and the cheaper it is to insulate, but it is not as strong. Texas A&M did a study on foam, and said that if a family just insulates their roof on their home, the cost of doing it will be repaid in about 5 years from energy savings, and they sprayed almost 2 million board feet in this test.

The other thing you gain in a conventional home with at least two inches of 1.5lbs foam is the increased strength. It will increase between 20% - 30% depending on the foam used. What it does, is really just completely glue the house together. Now you are talking about a home that is rated to stand up to say 120mph winds, and with good foam it's going to increase to around 150mph winds.



I am not sure if anyone else sprays foam under the slab. I do, and it is to keep the slab from sweating and gives us a place to staple the floor heat tubing to. Now all heat that runs in the slab will go into the dome, and not the ground. The ground will not suck any heat out of the dome at all. Then in the hot weather, you don't have concrete floors sweating. I'm sure you have seen garage floors wet when it gets hot. That is nothing more than vapor drive. Moisture going from hot to cold. Just like when you open a cold drink and set it on your table and it is full of sweat beads on the outside. The moisture in the air condensated on the cold surface of the bottle or can. That doesn't happen with a foam rubber can cooler. Samething with a concrete floor or wall and foam insulation. Wrap the concrete in foam, and no sweat, no sweat, no vapor drive and wet floors, and no musty smell. It's not rocket surgery.

The samething happens in a regular home in the basement. The basements are cooler because they are not insulated from the ground. The moisture goes to the cooler basement and condensates on the walls and your basement smells musty. This is one reason why they are using those insulated forms to help stop this and make the basement more useable.


There are no real "TYPES" to avoid, you just need to use the right foam for the right job. There is one supplier I will NEVER deal with again. They are UCSC out in AZ. Poor comstumer service to say the least. Unless they have changed in the past 6 or 7 years. I bought foam and foaming machines from them and NEVER again. I deal with Volatile Free now. Volatile Free Inc.




As far as spraying foam under a STEEL ROOF yes, you can. DO NOT spray foam under a roof with shingles. That foam will ruin your roof in a year. What happens is the foam will not let the heat from the shingles to go into your attic and then vent to the outside and your shingles will just melt.

On a steel roof, there is no problem, but you can't spray shotcrete up against that foam. You have nothing to hold the concrete up there like rebar. You need rebar and concrete to work together starting at your footing and going up. Even if you did do this with rebar, you have no way to create the need air pressure inside the structure to hold the wet concrete up on the ceiling until it sets up. You will need to cover that foam with something though, like drywall or something. It is code everywhere I think. Foam can not absorb hot or cold, it only reflects it. So, if you have a small fire from say a rag or something, EVERY BTU from that fire is reflected back onto any object that will absorb heat and start it on fire.

Let's say you have a two car garage, and in the middle of the floor you have some rags start on fire from welding. With in a VERY short time frame the heat inside you building will be 100's of degrees if you don't cover the foam with something like drywall. Drywall will absorb heat without burning the same way concrete will, and give you time to get the fire under control. This actually happened and isn't a story. Some rags caught on fire and spread to a couple other things, boxes or something. He ran to call the FD and get a fire extinguisher and when he ran back to the garage, he said it was like opening an oven. She burned to the ground.



You don't have to worry about how much time passes between coating on a dome. Seriously, you can start spraying one month and finsh it up a year later. You won't have any trouble with a cold joint. I can explain this more if you want, but I am getting long winded here. When we spray shotcrete, we usually do one coat a day that is about an inch thick. Sometime we go two or three days before we hit the same area again because the dome is so large. Actually, you need to worry more about putting on another coat too soon. You need to let the layers set up each time to at least 600psi. That is where you can scrape the CC with steel but not with your fingernail or something softer.

If you put it on sooner, what can happen is that foam does not allow any heat to escape and you can get some bigger cracks in the shell. It is cosmetic only, but still, why have them. Also, if it isn't strong enough to support the next layer of shotcrete, that air pressure will not hold up a few more tons of shotcrete and it will fall out. This is just a waste and a construction delay and nothing bad structurally. You just spray in more after that area sets up. Don't try to fill it in when it falls out. Just walk away and leave it. Fix it in a few hours, or more will fall out.


Mixing shotcrete is really an art if using smaller machines. If you do not have someone to show you, you will have trouble. I mean you need to really get an eye for what your sand and pea rock looks like to know how much cement you will need to add. We really got tired of this, so now EVERY dome is a nine bag mix and we have never had one bit of trouble since we started doing this. Granted it is over kill, but wasted time unplugging hoses is costly as well. You can avoid this by spending big money on bigger concrete pumps. I good Schwing concrete pump will pump concrete that is damn near set up already. They just cost as much or more as your home you are building, and those are the small ones.

The mix we use is about 700 lbs of sand, 140 lbs of 3/8 minus pea rock, and 2-3 bags cement depending on sand and pea rock and if it is the last coat and what finish we are shooting for. This makes 1/3 of a yard. You have to adjust as you go and develope an eye for the right mix and stickyness.

Sorry for the long post, but your questions are not one line answers. I mean I can give that, but really what's the point then, I am not going to waste my time with a half ass answer.

I'm not smoking anything, but I'm really not sure what I 'm looking at here in your drawing??? I'm guessing that the flat circle is the top of an underground dome with a tunnel? I'm also not sure what you mean by will it work. What are we talking about here?

When building underground, a septic and lift pumps are always something to consider. That is why I like to see where some one wants to build and then explain why it won't work in a certain location unless extra money is spent. Most of the time the fix is as easy as moving the site a short distance.

Most people are not building on completely flat land. Most sites have at least some hills to then somewhere. Remember, if you build another dome underground close to your homes with a tunnel, that bathroom in that underground dome/bunker will have a bathroom at the same level as a bathroom in the basement of a regular home. All we are looking for is to get a little earth over our heads for protection. We don't need 10' of overhead cover.

If our main home has just a few feet of change in level from our underground bunker to the above ground home, our bunker becomes nothing more than a basement which just happens to be connected with a tunnel. The dept of the bunker would be the same as a basement, and we have bathrooms in our basement. Does this make sense?

A tunnel is very easy and cheap to build. A tunnel that is 8' in diameter and 30' long will cost less than $5,100 to build and connect between the two domes after the domes are built. You will have plenty of storage in that tunnel as well if you want.


I believe you are talking about when I said, it's cheaper to build another dome underground than it is to build a thick concrete floor. The cost between the extra stem wall digging deeper, and that huge floor would cost more than another building, and not give you the same protection.

LOL, no, I thought it was me who might have been smoking something!





Yes, sorry... I replied before reading to the end of the thread and, when doing that this morning on my cell phone, saw that you had already addressed [pretty much] this exact thing in one of your subsequent posts.  By the time I got to a computer to edit it out/away, you'd already taken time to respond.




I forget.  Everywhere I've ever lived has been flat.  I grew up in South Texas, where everything was flat, and I moved 10 hours away (lower Texas Panhandle), where everything is... flat.



The in-laws recently built in the Texas Hill Country (Central TX) where it's pretty hilly, and I was actually about to start talking to them about domes, when my father-in-law called my wife and told her that my mother-in-law had picked a [custom] floor plan, contracted a builder, and broken ground, all in the span of a week.  It [surprise, surprise] didn't turn out quite like they'd expected, and her custom house ended up costing more than double what she told everyone it was going to cost.  I *weep* when I think what they ended up with, versus what they could have had in a dome home...



My mother and step-dad are about to retire, move out of Texas, and start building in Kentucky, sometime in late 2010 or early 2011.  Just working in the summers, they have already cleared their hilltop, dug a pond, and are pretty much done with site prep.  I've sent them the link to this thread...




Yes.  I suck at drawing, but what I was trying to ask was if, instead of digging down super-far and having a basement and an even deeper sub-basement (the actual shelter), another option might be to have the shelter at the same level (more or less) as the actual basement.  I was trying to ask if that alternative might work for him, not whether it would work mechanically, because I thought you had already stated earlier in the thread that it would.




That's one of the highlights, to me anyway, of separate domes w/ a tunnel connector.




That may have been it.  I knew it had something to do w/ a stem wall, and being more expensive, but I guess I [mis-]remembered it as "stem wall + regular dome" being more expensive than "regular dome alone."



Thanks for all your help over the years, not just in this thread, but in all the others which have, sadly, gone to the Elysian Fields of the archive server.





 

Thank you very much for taking the time to make a very informative post and answer my long winded questions.

I didn't realize it was the air pressure keeping the concrete up while it cures, I was thinking the air pressure was just to give the dome its shape while spraying foam and afterward, the air pressure was no longer needed.... interesting.

I have a few more questions if you don't mind.

As for the foam, is "open cell" foam just the light weight foam and the "closed cell" foam the heavier weight foam?
Also, you mentioned a supplier to avoid, could you list some suppliers that are good to deal with?  
Is the price for foam comperable from company to company?  
What should I expect to pay per board foot?  
Are there companies you like that cater to consumers?  

I've noticed that a lot of suppliers from googleing, require the purchase of their equipment.  I was looking at this company that sells disposable kits straight to consumers.  What do you think of a system like that?

http://www.rhhfoamsystems.com/index.php

Wise_Jake,

No, I should have wrote, I wasn't smoking anything EITHER.    Basically meaning I had a clear head and still a little lost at what you were saying.

I am sorry to hear about your family getting shafted like that. I know many people who do that sort of thing, and almost all dome builders do it because there aren't any who can actually build worth a damn. Those that can REALLY charge. The sad part is, they cost so damn little to build and even if they charge $75psf, they make a damn good living. It all boils down to greed.

When I build and it is for a family who is doing it on a shoe string, I always try to get them to look at getting their home in a different way to ensure they have the money to build and pay for it over the years. Just because the bank gives you the money, doesn't mean you can afford it..

Here is what I have said to them. If you have a loan for $250,000, let's take that money and build small rentals at MY COST. We can easily get up 8 duplexes or 16 rentals for that money at MY COST. They are about 600sf each. Let's charge $525 a month rent and make $8400. The value of them is almost $1m at $100psf.

Now since we are cash flowing and have almost $750,000 in equity, let's take more of that easy money the banks were handing out back then, and build more. Say we get another $600,000. Now we have $850,000 against the property, and can build another 20 duplexes for a total of 28 duplexes and 56 rentals making $29,400 a month. We can at this point damn near build a rental a month with this income and never talk to the bank again.

The new appraised value is $3.36M and our loan payment on $850,000 is about $5,000 a month. That leaves us around $24,000 a month or $12,000 a month each.

Now you take your $12,000 and I will build you your home at MY COST again with your cash flow.

Now what you have done is taken money from the bank and made it make you money, and you have a home free and clear with no payments, and an income most people dream of having. That $250,000 loan is an asset and not a liability.

I have ALWAYS said NEVER take money from the bank to buy a home or any crap like that. Any money you get from the bank, you better have a plan for it to make you money or you are a slave to the bankl for the better part of your life.

What I was doing was trying to ensure their security for the future as well as mine. I knew this housing bubble back then was not going to keep going, and when it came down, I want all of us to have residual income. So I planned to put myself and others in a position to take advantage of what was coming. People need a few things, food and water, and a CHEAP place to live. Heck, we could drop our rent to even less if we had to and still make great money and NEVER have an opening.

I designed and priced the rentals so that a couple each making $8 an hour or $16 an hour total, and paying $525 a month, are only laying out 18.9% of their gross in housing. The domes operate so cheaply, that they will be at about 20% of their gross income to live there. How many can say that? You would never have an opening.

I know some say it is a lot of work running the place and this and that, and I say fine, go to your J-O-B everyday I don't care, because that must be much more fun and secure. Besides, anyone to lazy to want to make $12,000 a month working for themselves, and the ability to increase that money at any given time if they want just by building more and never talking to the bank again, is someone I don't want to be around anyway.

Everything I do is based on people making $8 an hour, EVERYTHING. That is because those are the only jobs that are going to be left for the most part in this country. I mean you can pretend things will get better, and you can pretend your 401K will be there along with the stock market, but at some point reality will force you to pull your head out of your ass or sand and wake up. Then what are you going to do?

You know, it is NOT hard to become a millionaire at all if you apply common sense and you're willing to work for it. It is hard to make ends meet when you are a slave to a bank.







Yes, air pressure holds the shotcrete up. We need about 1/13th of a psi or about 12 pounds per square foot, to hold one inch of shotcrete to the top of the dome.

Open cell foam is nothing more than a sponge. It has no strength at all. Close cell foam is the only thing we can use. Even the light weigh foam is still close cell. as the weigh gets lighter, the foam get spongier. You can tell a huge difference.

I did add the link in my other post to who I buy foam from. I deal with just them now. I don't screw around.

Yes, it is pretty close I guess. Again, when I buy foam it is in set of 40 or a semi load. So I get a pretty good price on it.

Price on foam is really up to the man spraying it. I think buying foam on a smaller scale, they are getting hit for about $1500 or $1600 a set, but I maybe wrong here. I know EPA changed the rules for blowing agents in the foam and that drove the cost up some. If you are using say 1.5lbs foam it is costing the man spraying it about $0.50 per foot. Most will at least double that cost. So if you want foam 2'' thick on a home that say 8' x 20' x 40' it will cost you around $4000 - $4500 to insulate the walls in your home and another say $2500 in the ceiling above the living area. While this sounds like a lot, you make this cost up in savings for heating and cooling in about 5-7 years. Less if the cost to heat and cool keeps climbing. Then it is money in your pocket. Real cost on this is just a little over one set of foam. So if he is paying $1600 a set, and charges $2.25 for 2'' of 1.5lbs foam he is making a little more than double his money which is pretty much the going rate, but the more you want done, the more wiggle room you will have to dicker with him on.

Good luck finding anyone who really gives a shit about you after cashing your check.  

I have seen that foam, but I have no experience with it. Foam is a VERY VERY fickle bitch and does not play well at all with anything when in a liquid state, but 3 seconds after it is applied, she will put up with just about anything from anyone. I am unsure how forgiving that foam is, but I would ask them some serious hard questions about it before I bought it. You can waste a lot of foam trying to get everything to work. I have seen piles of foam a few feet high outside a dome when the machine or foam gets a hair up its ass, and these are men who have sprayed foam for many many years and they are having trouble.



Also, how did I become a bronze memeber? I never paid for that??? Or am I just seeing things and screwed up as polio??

1_BIG_BUNKER do you think a dome building is a good (economical) alternative for a barn /shop as opposed to a common steel building (say @ 50'x80' size)?
Have you seen or built any with good floor plans?

Well, I am not sure. I can give you an idea what it would cost, and then you would have to weigh it all out yourself as far as the pros and cons for what you want to use it for. To me, a barn is where we kept our cattle. A machine shed is where we fix what we broke. So a barn - shop set up is a little new to me.

I will lay out a dome that is 75' x 35'. It has 4,415 sf of floor in it. I would have this on a 8' stem wall. You can have a second floor in part of the dome if you want or all of it depending on what you need for a shop.

The cost will be about:
Airform............................$21,000
Floor..............................$9,500  This is a 6'' thick floor
Foam...............................$13,500
Rebar..............................$12,200
Shotcrete........................$11,000
Misc................................$12,800  This is very high, but better to be safe

Total.............................................$80,000 This is about $18.12 psf.



This is rounded up, and no labor, but four men could easily do this in four weeks max. So four men at say $15 an hour is about $10,000.


To give you an idea what the inside would look like, here is a church in Alaska that is 80' x 27' with no stem wall. Read the article and they said that they are paying about $72 a month to heat the church in Alaska. If heating and cooling are something you need to do, then this is pretty important if you ask me. Operating costs on a building can make or break a business pretty fast. Insurance on the building is nothing. Most people just have liabilty, and cover their contents and call it good. Unless the bank holds the note, then they make you get insurance.

Article

Pictures

Onething thing to consider when building something like this, is to think ahead. Remember, this building is pretty big and will be around for a long long time, and may not always be a shop. In 100 or 150 years, if the country and world are still around, someone is going to be pissed that you didn't add in more plumbing for bathrooms when they want to make a big house or rentals out of it.

This is just me thinking out loud, but when you design the shop or whatever, have a back up plan to make it into something else like housing. Install the plumbing right away because you won't be doing it after the fact. You can have a building with around 8,000sf of living area with a second floor if you wanted to, but what good is it if you don't have flush toilets. Just install the plumbing at grade, cap it, and forget it.

As far as planning for extra doors and windows, don't worry about it, just take a concrete saw and cut a damn hole in the dome. Really, the hole is so small the dome doesn't care one bit, so long as you stay with in reason and not cut a 20' hole in the thing. Just normal doors and windows, you won't hurt a thing.

If you are serious, and want more info, just let me know and I can email you some of my floors plans that I had drawn up. This will show you how you can have some damn nice apartments in that dome.

I hope this helped.

Thank you!
Machine shed / man cave / the place where we don't mess with daddy's stuff... ever.

boat storage/trailer storage/tractor storage/mower storage/jeep storage/reload room/woodwork shop/metal shop/tool storage/and finally actual storage storage/ with a small bathroom

I'm assuming someone took a moment to thank you for all of the assistance you've selflessly given to arfcommers in the years since you've been posting here.



In hindsight, I wish I could say it was me, but it wasn't.  It seems like such an obvious thing to do, now...



 

Excellent infor I've read every page a few times...

1BB Thank you for all the insiteful information! Its appriciated more than you know.

hmm foundation question...

Footers in colder climate.

Maine generally has 6-8 foot footer depth from the frost. Is a dome slab structure enough to overcome this or are excavation costs a necessary tack on?

Hell no, frost will lift that dome with ease.

The good news is you don't have to spend money to dig down below the frost line and pour a lot more concrete. What we do is we spray foam out from the side of the dome or any slab. What this does is increase the distance the frost has to drive or travel to get under the slab and lift it.

Below is how you do it.

You spray foam, shown in purple, down on the ground before pouring your footing and slab, shown in black. You do a normal footing, say 2' deep in the ground, in brown.

Then attach the dome, in red, to the footing and build the dome shell.

While the footing are still exposed, you spray more foam around the footing and out from the footing about four feet.

Frost can not go through foam, so it has to go down two feet at the very end of the foam and four feet to reach the footing. This is equal to a six foot frost depth.

It doesn't matter if frost has to travel down or across, so long as it have to travel the same length as what your frost depth is for your area to get to the slab to move it. The ground under the foam will be well above freezing because it is insulated from the colder temps above the foam. Since it is ground temp of around 55 degrees under the foam by the slab, there is no freezing and expanding of the ground and no heaving of the slab.

It takes less than an hour to spray the foam around the dome or any slab really, and be done. I always go down no less than two feet, and taper the foam down away from the slab. This is because few people have enough ambition to dig a hole two feet deep to plant a bush.

I hope I explained that clearly, it is late and I am tired.

The second picture is showing the men insulating every bit of concrete from the outside. No concrete is ever exposed to outside temps anywhere on a dome when I build them.We put tape on the dome so any over spray is just pealed off with the tape for an nice even edge. They will spray more foam out from the footing as well.

The bottom picture kind of shows the foam around the outside to. It will be back filled about even with the foam line. The guy up on the dome is running screws to hold a skylight frame to the top of the dome. There is no foam or concrete inside the dome. He is being held up just by air pressure. He could walk on the dome is he wanted to. I know it doesn't look to safe with him being on a ladder and held up by a skidsteer bucket, but don't worry it's okay, he was wearing his safety glasses.

1BB, Great information here!

I've got a question about the foam.  I've got a traditional stick built home w/ a poured concrete basement.  I'm finishing the basement, and have seen some spray foam insulation products. Is the foam you're talking about the same as what would be used inside a home?  Is foam a superior product to use in my application (to rolled batt fiberglass, or foam board)?

Thanks!
K

Wow, 1BB, still providing great information in this outstanding thread!



I was just wondering where (i.e. in what state) the above pics were from?

The foam is the same. So long as it is heated to around 115 degrees and sprayed under pressure, about 800 psi, it is the same foam. The only thing that could change is density of the foam. basically, what pound foam is it.

I am not getting into a big long post about the differences between batting and foam, but foam is much much better. I actually wrote a LOOOONG post explaining the difference, but I decided it was way to long for most people to read, so I will just tell you a story that happened with two of my friends. If you want the original post, I saved it and can email it to you.

Two of my friends were building conventional homes that were exactly the same except for minor changes to the interiors. I was looking at their plans and said they should spray foam inside the walls for insulation. Of course the first question was how much? I did some quick math and it was going to cost them about $3000 just for the foam. I would do it for free as we were friends.

My cheap buddy said no, he was going to put in the "GOOD" batting insulation, whatever that is, and the other asked more questions about the foam. Long story short, he wanted me to spray his home with foam.

About 8 months later my cheap friend came to me and said you know, I think I may have made a mistake. I said how? He said after the first winter the two of them compared heating bills to see the difference between foam and batting. He said his cost to heat the home in northern Wisconsin was about $1150 and our friend who had me spray foam in his home heated all winter for just a hair over $300.

I said, yes, and just wait until you get your air conditioning bill this summer and compare those two bills. He didn't find the humor in it at all. So I had to keep rubbing it in, and said, well look at the bright side, it could be worse, I mean at least you put the "GOOD" batting insulation in. Again, no humor was found.

Sometimes you just can't talk to people and explain things to them. I don't care if people insulate their home with old Playboy mags, all I can do it show you and you have to choose how to spend you money.

You either spend more up front and a little over time or a little up front and a lot over time. It's really that simple.

Plus, this is something that foam does that few talk about. It glues your home together and increases its strength by 20%. Does batting do that?


Foam board is better than batting by far, but still is lacking. It can't seal up anything and you will always have leakage. Batting is something I wouldn't use in a barn. It was good in its day, but its day has come and gone with the Model T.







I'm glad you are enjoying the posts. Sometimes I know I write to much, but I like to explain things VERY clearly.

That one was built in Northern Wisconsin.

Now if only the economy would settle down enough that i could stop worrying about losing my job and needing to be mobile I could get to starting me a domestead

one question that I am not sure has come up so far, how are they for fire resistance externally? wildfire, restless native with molotovs etc?

also, how about connecting them together to make a gradually expanding house as cash flow allows? just align the openings and seal over with polyurea?

I love this thread!

They hold up very well against fires.

Monolithic Dome Suffers Slight Scorching In Oklahoma Wildfire That Destroys Five Homes

California Wildfire


Adding on more domes is no problem if you plan for it. If you don't, you just make more work for yourself. Seriously, they are so over engineered now that you can just grab a concrete saw and cut a damn hole in it and add on. I am not going to get into how to do that here because it wouldn't make much sense to you. Just plan ahead and make sure you don't have any wiring or anything where you want to cut a hole.

The only time I would start to worry is if you wanted to cut a hole larger than about 10-12 feet across and didn't plan for that hole while building the shell. I think at that point you would see some small cracks above the cut out. It will only crack a short ways and that's about it, but I wouldn't go any bigger than that. Plus, to add on, how big of a hole do you really need?

The cracks can usually be covered with a coat of paint and never seen again. If they are bigger, just fill them in with a good caulk and paint over it and it will be fine.

By far, the easiest thing to do is plan ahead. We frame in and build a hole for future use. It is foamed in with rebar sticking out so when you want to add on, everything is there. Then we cover it with plywood and then shotcrete over it. You never know it is there. Then at the bottom we cut two small grooves in the wet shotcrete that you really don't notice, and that is to mark both sides of the door so you can find it again.

Knock the shotcrete off, cut out the plywood, bend your rebar back, cut out the foam and carefully cut the airform because you need that to attach to the add on you are doing. That's it in a nutshell.

Below I scanned a few pictures for a dome we built about ten years ago. You can see the door and how we have plywood covering the foam that was already sprayed. The extra rebar isn't run inside the door yet, but it was and was just laid flat. That rebar in the door is what we use to tie our add on dome into the main dome shell.

Make sense?

You can also see how big of a hole you can put in them. Actually, that's not that big of a hole. The 2x8's will come out after we are done spraying shotcrete. You have to support it until it has a couple coats on it or the wet shotcrete will make it sag. That's a lot of weight, and when wet it has zero strength.

These things are always impressive. If my new job comes though... I'll be getting one in about two years... Thanks again 1BB for the insight and the pictures.

1BB, here's a question on foam.

We are thinking about insulating a metal bldg [~6000 sq ft combined surface area, end walls and arched walls] and the insulation companies want ~70 cents per 1 inch thick by 12"x12" foam, installed.

R value ~6.7 per inch 1" thickness.

Is there any practical way to get the foam cheaper? I thought about buying a foaming machine but only do work for myself so it probably wouldn't pay.

Suggestions?

No, it wouldn't pay to buy your own machine. Hoses alone run about $20 a foot for the machines, and you will need at least 100'. I have 250 feet for each machine. My spray guns are around $1200 each. The machines themselves are running around $20,000 for an average one. You need a large two stage AC. Then you have to have something to put them in like a trailer. Then you better use that machine and not let it sit around.

Actually, that price they gave you is not that bad really. Which leads me to believe they are spraying a very light weight foam. I would ask them what pound density foam they are spraying. Many are using a very light foam, around .75 pound. That is not very good for what you want. You want them to be spraying at least 1.25 pound foam and 1.5 pound foam is better.

The high the pound foam, the less coverage you get but the stronger the foam is. The light stuff is better than nothing but it is not strong and kind of spongy. I spray 2.5 pound foam and a set will cover about 2900 board feet and my cost on it is about $1100 a set when I buy a truck load.

Now if I spray .75 pound foam, my coverage goes way way up. I am not sure how much because I never spray that crap. I know they get around 7000-8000 board feet of coverage with some of that stuff. More coverage means more profit.

Almost every foamer will charge you twice what he pays for foam. So if your guy is getting his foam for around the same price as me, say $1100 a set, and he is charging you $0.70 a foot, that means he is paying $0.35 a foot for foam. Take $1100 divided by $0.35 and you get around 3100 board feet per set. That tells me he is using a good strong foam and giving you a fair price.

Ask to see a sample of what the foam will be like that they are spraying



Also, do not pay any attention to the "R" value as that means nothing really. You see, the "R" value is a number that Owens Corning uses in batting. They test batting in a lab in zero wind and zero humidity. Well, that's not real world people. In the real world we have wind and water. Get that batting even slightly moist and tell me how well it insulates.

What you really want to know is what's called the "K" value but few know anything about it or ever heard of it. What the "K" value is, is a measurement of any materials ability to transfer a hot or cold temp. The harder it is for that material to transfer that temp change to the other side, the better it insulates. Well, those ratings are like .14 and that's not a "COOL" selling point. People love big numbers, so ASTM went to the "R" value and it works great in a lab. People want to say BIG numbers like an "R-60" and really they have no idea what that means. Just ask them. Ask them how do you come up with that number? No one knows. Even foamers have no clue why foam insulates so well. They just know it does.

You can not in anyway define insulation by one number. What if I had some land to sell you for $20,000 and I told you it was an 8. You buy it or would ask 8 what? Square acres, miles, feet, and by the way, where the hell is it, in the middle of a desert, a swamp or down town Dallas? There is just to many other factors that need to be taken into account to accurately describe what it is and its value. The same thing with insulation.

Take batting, and soak it down and put it in a 20 mph wind and let me know how what your heating bill is. Do that with foam and your heating bill will be the same. Foam doesn't care. Batting doesn't seal up a home, foam does. Talk about vapor drive with batting and then with foam, again, it can't compete.

So, don't take that "R" value to heart as it means little in the real world. However it seriously favors batting in the lab, and plus saying a BIG number always sounds cool and it sells.

If you want, I will try to explain the difference between the two, K and R, but this post is pretty long already I see. Just let me know. It is rather long and boring unless you are into that sort of thing. I am, but I know 99.9% couldn't careless they just want low heating and cooling bills.

Thanks 1BB. I'll save you the time, and research K-factors.

I asked the installer the density and he told me it was the high density. In any case I will ask for samples and measure the volume by water displacement and calculate the density. And let the installer know I will test -AFTER the contract is signed.

Good info, thanks!  If you've already written up the diff. btwn foam and batt, I'd appreciate reading it.  Incoming IM w/ my e-mail address.  Thanks!

I think you might just convince me to do my basement walls as well as the exterior walls of my house.  Any info on installers who pump in the foam from the outside and displace the existing batt insulation?  Pro's/Con's?  Good price?

Thanks!
K

I am not sure you could get the foam to displace your original blown-in insulation. It sticks to everything, and it expands...so even if you attempted it, I think you would wind up replacing all of your drywall after it expands and breaks your walls.

double tap

These guys do it.  I suppose it may depend on what type of foam is used?  (ie, the diff btwn Great Stuff "crack and gap" filler and their 'Doors and Windows" foam)

K

First I think I will explain how foam works so you can gat a better understanding of it.

I like to explain foam as in the old phone booths and college students. I am sure you have heard or even tried to see how many students you could fit in a phone booth, well foam is kind of like that.

Foam has what's calle blowing agents in it. That is basically what cause foam to expand to make a close bubble or cell. That bubble or cell will now be our phone booth.

The blowing agents are the students.

Now we will line up a few phone booths side by side.

Then one one side we will apply heat to the booth. Those students who are exposed to the heat want to move to the back side of the booth to get away from the heat and cool off and transfer some of that heat to the next cell, or booth in this case.

The problem is that those students, or blowing agents are packed pretty tight inside the cell or booth and rotating is not very easy and is slow to happen. While they are packed tightly, they still have areas where there is a void and things are able to move a little.

They slowly make their way around to the other side of the cell or booth and they transfer that heat to the next cell or booth. Then the whole process starts all over again, but this time it happens even slower because that student or blowing agent is not receiving the same amount of heat as the original cell or booth with students or blowing agents. Since college kids are lazy, they are in no hurry to move to the other side because the heat is not that bad, and blowing agents are the same way. The natural friction between molecules will slow to a stop after a short time and all heat transfer will cease.

This is basically how foam works and shows how it is a very poor conductor of heat transfer. It does not really trap air in an air space like batting or wool, it just makes it very hard for heat to move through it.

Not only is it hard for heat to transfer through it, it is IMPOSSIBLE for wind to pass through it. Remember how they test the "R" fact in a lab? NO wind and NO moisture? Well, with foam, soak it down and hit it with a 50mph wind and see what happens, NOTHING. It is a CLOSED cell bubble meaning water proof.

Batting on the other hand is nothing more than spun fiberglass. That is the samething we make furnace filters with. Why do we use it to make filters? Because of LOW IMPEDANCE to air flow. That means air flows very easy through the filter. So basically we wrap our house with a big furnace filter to filter out the bugs as the wind blows through it. Now tell me what your NEW "R" value is with wind???? Sure, they put up plastic to try and block the wind, but now you have a vapor barrier and catching the moisture in the worst possible place, by your batting. Plus it doesn't stop it all anyway. Moisture, and wind are really bad for batting.

Now have the family cooking, taking showers, doing the wash and all that other stuff they do and put moisture into the air like breathing. You also have the rain from outside wanting to get into a cooler home in the summer time. This all adds up. We now have to worry about whats called vapor drive. That's where moisture goes from hot to cold. An example is a can of coke in the summer time. You set it on the table and in seconds, the outside is wet. That is the moisture in the air condensating on the colder can. You can see garage floors do this in the summer. You basement does it because it is cooler. Moisture condensates and you get a musty basement smell. How many times have you heard people say that their home is dry in the winter? Well, no magic, all the moisture is going through your walls to get to the colder outside air. A lot of that is getting trapped by the plastic in your walls next to your insulation. Again, what's your NEW "R" value rating??

We just keep putting a bandaid on top of a bandaid trying to fix the unfixable problem with batting. Batting was great in its time, but its time has pasted.

With foam, you have none of these problems because nothing and I mean nothing can affect foam. Moisture does not condensate on foam, because it is the same temp as the room so you don't have vapor drive. Wind can not blow through it because it is closed cell, and glued to every where it's sprayed.  These are the two major factors for insulation that we really need to worry about. There is also convection where the air flow carried heat up through the fibers of the insulation and vents it out. You loose heat that way as well, but this post is getting pretty long now.

I hope you can start to see and understand how foam works compared to batting. There is so much more to consider when thinking about insulation than just one number. That one number is very misleading. While the "R" value may not look good for foam in a lab test, batting looks even worse in real world, but no one tests it there. The real proof and bottom line is not the "R" number that some bone head who has no clue what it even is or how they got it, but the number at the bottom of the bill you get each month for heating and cooling. If I told you your home had an "R" value of 1 but your heating bill is going to be HALF what it was before, what number do you care about the most?

Just know that if there was a better insulation, NASA would use it on their space shuttle to protect it on reentry. I think the world has seen what happens to a shuttle when they have lost even a very small amount of foam, it is a complete and total destruction of the craft EVERYTIME. If foam is good enough for NASA, it's good enough for your home.





GTL is EXACTLY right. That foam will not be stopped by a wall. It will push the drywall right off the studs. That foam can glue your home together and save it in high winds, or applied wrong, can cost you A LOT of money repairing your home. Foam is like fire, it makes a great servant and a cruel master.

You need to remove anything in the wall before spraying it. Even if the wall is hollow and you know this for a fact, I would still spray a lighter weight foam. Just because it is spongier as I said before, and will compress between a wall and give you a little forgiveness for expansion.

The best thing to do is spray it before you drywall it. Put a layer of tape on EVERY stud before you spray, or you may get over spray on the studs. When this happens the drywall can look wavy and uneven. This may not be a problem with smaller machines that move small amounts of foam, but what I have moves 40 pounds of foam a minute. I can empty a set, two 55 gallon drums in under 30 minutes. Then again I am covering a dome and not inbetween studs. My spray pattern is three feet wide at the sweet spot. I'm not really set up for small foaming jobs.

Once you are done spraying foam, peel off the tape and you have clean studs to hang drywall on.

1_B_B,

After reading your post, I got into a discussion with a buddy who is building his own home.  He put in the board insulation and filled with can foam between cracks.  

My understanding of your explanation is that its like wool and an insulated goretex jacket.  Both have great insulating properties, but their effectiveness would be measured in different ways.

Yes, you are on the right track. Gortex is more of a wind and water block than it is a heat transfer stopping insulation, but yes, they both insulate but in different ways.

You would want wool in just cold weather when it wasn't raining and high winds.

Gortex you would want if it was wet and cooler out.

If you had a flexible foam jacket, you have both. The wet, rain, and wind doesn't pass through it and your heat loss is at near zero. Kind of like those survival suits they have for people out at sea. They are foam, so they float because the are close cell and nothing can get in them, and they let almost no body heat escape. Even wool and gortex won't do much to help you survive those conditions.

You have to stop heat transfer and foam is the only real way to do that in EVERY type of environment your home will see.

You see, while foam may only have an "R" 12 rating, it keeps that rating for every single type of situation your home will be in. Now batting, while it may have an R-30 rating in a lab or controlled test area, in the real world when other factors come into play, it drops through the basement. Had batting been able to perform in all conditions, your heating and cooling bills would be pennies a month.