does any one have suggestions on alternates to concrete for a safe room ceiling?  

my situation is we are building a new house and the design let me add 1 concrete wall in the basement and create a 16.5ft x 26ft  safe room.  the problem is the span is to wide and the room to big for a regular concrete cap. i would have to be lightweight concrete and tie to the floor joist above lowering the ceiling or have the floor joist below making it not a "sealed" room.

so im considering just pouring the wall to section off the room and putting some kind of steel below the floor joist. i want to add that my primary goal of the safe room is fire protection first, theft second I say that because if some one wants something bad enough they will get it concrete or not. and even with just the wall they would have to cut through the master bedroom floor to get in from above.  

so basically what is a semi fire resistant ceiling i could add to the bottom of floor joist over the room.

4 layers of 5/8" sheetrock will get you a 2 hour fire rating but the joists will still be the weak link.

You could double up on fire treated joists to minimize the issue.

I would add steel ibeams and lolly columns to support the span so you can still pour a ceiling, but if you can't do that, look into spraying the floor joists and subfloor on all sides with ceasefire epoxy before installing the subfloor on top of the joists.

My first thought was,  that's not a large unsupported span. Do it at work all the time, however the "ceiling" is also the" floor" of the next level. Add a beam or two and pour a suspended concrete slab over the top and eliminate the floor joists in that section.

If you're absolutely stuck doing floor joists, I'd suggest using steel floor joists , like steel studs, but a lot heavier gauge,  and maybe steel pan decking with several layers of drywall inside as noted by another poster to increase the fire resistance.

do you happen to have a link to steel pan decking?

www.metaldecksupply.com/locations/indiana/

Composite steel decking will span that easily. What did your structural engineer say?

His structural engineer (if he contacted one) said: “No problem, a concrete roof is easy to do on new construction. But are you sure you want to pay what it’s going to cost?”

An engineer could easily design (size) a steel girder that would cut the slab span in half (from 16'-6" to 8'-3").  I would try to select a girder that is the same depth as the concrete slab (vault lid).  Select concrete cast-in-place steel forms (pans) that accommodate the design slab thickness (weight of wet concrete) and span (8'-6").  Seven to 10 foot is a pretty typical span for cast-in-place forms.  Then set the pans on the bottom flange of the (WF) girder.  If I were doing it, I would design the concrete slab to span the whole 16'-6" (to ignore the steel girder once the concrete sets).  This can easily be done by cutting (drilling) holes in the girder’s web to pass the rebar through.  The reinforcing steel would need to be designed to carry the dead load (slab weight) and any live loads that may occur.  

The main reason I would ignore the steel girder in my design is that steel is the least fire resistant building material used by man.  Steel does not burn, but you do not have to raise its temperature very much to take a beam that is close to its design yield strength to failure.  Steel’s strength decreases rapidly as its temperature increases.

You could also leave out the steel girder and simply use 16'-6" long cast-in-place pans.  The down side to this method is that the labor and materials required to temporarily brace the pans, until the concrete set, might exceed the cost of the steel girder.  It would take a lot of bracing to support that many tons of wet concrete.

And before anybody asks, yes I am a licensed Professional Engineer who has done a lot of this type of work (I designed about 50 bridges back when the Interstate system was being built).  But I am not licensed in Indiana and even if I was, I am not your engineer.  An engineer can design just about anything a client wants, the question is: “Is the client willing to pay for it?”

The things that would concern me about your project (other than cost) are how do you keep the enclosed area dry (low humidity) and how do you get enough air flow (ventilation) to make the area liveable without worrying about sucking flames into the area during a fire?

Hope I helped.  If not, at least I gave your more things to think about.

Maybe 10 man hours for a guy who knows what he's doing and a guy to help him ( hold stuff plumb while he nails it, cut material etc) for a deck that size.

Using either :

Ellis Shores (4x4s with a set of gravity clamps that bind up the 4x4s, and using 4x6 stringers and 4x4 joists and 3/4" plywood.



Or Shore-X/WACO shoring  (like frame scaffold but stronger) and using 4x6 stringers and 4x4 joists and 3/4" plywood.



The plywood might be harder to rent but it's possible someone rents it . I could probably source some locally if I tried, but this is what I do for work so I know some people who could possibly make me a deal.


There are also systems where the plywood is panelized, like Peri Skydeck or Aluma-Systems Alumadek.
Rent enough material to get 99% of the deck done and then cut in 3/4" plywood fillers with a pinned on 2x4 ledger around 2 sides of the perimeter (2 sides of the box are Alumadek butted up to the existing concrete walls)

There are also the ICF forms which I think are pretty damn cool, but not practical in large commercial applications, but ideal for residential ones. Might be the solution for the OP, although I have no clue on the pricing.







There are a lot of options.

You can also take a look at precast concrete planks.

Why not weld together some 1/4" sheets of steel welded to some I beams? Fireproof, secure and strong.

This project was a roughly 50 foot by 50 foot vault where the ceiling of the vault was also the floor of a large garage.  Anything is possibly if your check will clear.  There are certainly alternatives to concrete, but most of them are more expensive than concrete when it's all said and done.

Tag. I'm doing the same thing. 16x16 though.

I have been looking at heavy corrugated roofing. Concrete ends up creating a whole slew of issues during construction and I want to keep my budget somewhat decent.

We're doing something similar in our addition except it's going to be 10'x10'. My problem is poured concrete might not be in the budget for doing the ceiling.

Any other alternatives to the poured ceiling? How fire resistant would the sheetrock method be?

What gauge and what "A", "B", "F" or "N" decking would you suggest for the ceiling?

Whatever your engineer specifies.  You'll probably not want the ceiling to collapse.