So I live in Indiana , can I build a garage on a 4" thick concrete pad and the building hold up over freeze thaw cycles ? I've been told yes and been told no. Some say needs to have 36" deep headers poured 12" wide around perimeter. Any input? Just a basic no fills car cover garage. -Thanks

What you are describing is just a 4" driveway with a metal carport awening. Will it work...probably. Depending on your existing soil...that might be okay. I would recommend doing some beams though....if you want the concrete pad to last.

If you think you will ever want a vehicle lift installed, may want to up that to 6in.

Does your pad have footings around the edges?

If not, the weight of walls, roof, and snow load will all press on the edges of the pad and break the edges.

This if your roof is anything more than a metal awening.

If the cover is anything more than one of those metal ones you see at hardware stores then your walls and roof will push the edges down and break them.  If you want to do it correctly pour footings around the edges.  I'm not sure what the freeze depth is for Indiana, but here in Missouri it is 30"

Normally on a monolithic slab you want thicker edges to support things.   Consider maybe a 12" edge 16" wide or so.    In the field of the slab, 4" is plenty for normal autos or light trucks.    Put mesh or rebar in it, not fibermesh alone.  Mesh is ok if it's held up off of the fine grade, it's worthless if it isn't.  In addition to mesh / bar in the slab, run a couple #4 bar continuous 3" off the fines in the thickened edge around the perimeter.  I wouldn't go any thinner than 8" thick at the thickened edge.  

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You will have the risk of frost heave of the slab edges.  make sure the soil drains well and has a good free draining, compacted,  gravel cushion under the slab and footings.


If you absolutely cannot tolerate any heave or cracks, then put in a full foundation wall to frost depth.

what does this mean?

Have you considered a gravel pad with concrete footings for a metal car port?

Just to clarify...  Is this an enclosed wood framed garage or just a roof system?

What I meant was a basic wooden structure garage with door. Just no fancy lifts , hoist, etc.  So my plan is to have the pad poured and then I will build a garage with lumber on it. Sounds like 36" footers will be needed.

It might hold up - if the garage is just for storing motorcycles and lawn mowers.

I only have one garage.

It's sitting on nearly the top of the hill, so no problems with water sitting in the soil for long.

I live in central VA, so it seldom goes below zero and even when it goes below freezing the ground seldom freezes (and then just a couple inches) for more than a day or two.)

I was told that fiber reinforced concrete would be just find at 4" of thickness for my pole barn/garage floor.

The concrete sits on several inches of limestone gravel.

None of the pole barn/garage walls weight is on the concrete.

My concrete floor has quite a few cracks in it.  The only good news is the cracks seemed to have stopped after the several I had finally ran out to the edges of the pad in one direction or the other.

I have a buddy that 4" was enough for his garage (starndard footer/cinderblock foundation with gravel under the concrete floor) but he wanted heavy ga. screen wire in his anyway.  Even with the screenwire and the 4" of fiber reinforced concrete his floors cracked.  Hell, he doesn't even really use it for a garage.  He's got a mostly disassembled 67 Chevelle SS on one side of it and the other side is used for his band's practice area.

I think cracks are something you just have to live with, unless you get lucky.

Good points a couple posts up.  

I wouldn't do a flat 4" slab with a full stick build.   At least go with the perimeter thickened "Alaskan" or monolithic slab.    That would be stronger.    Stronger yet  is footing to below the frost line then they pour the inside slab.   A two part pour so it's more costly in time and materials.  

I would have done the footings and slab on mine but I simply have too much bedrock to dig to depth completely.  I did the monolithic with IIRC a 18x 12" haunch and a six inch slab.  The haunch had two rebar low and three high all the way around and rebar on chairs spaced throughout the slab.   My contractor kept pushing for the mesh to make his job easier.    I was firm and stuck to my rebar plan.  I went so far as to help wire tying all the rebar and placing the chairs so I knew it wasn't insufficient.   My concrete also had fiber.  One year so far and no cracks.    I stuck with the rebar because my site was cut and fill on a bit of slope.   I also had the stone fill rolled in in six inch lifts.   When the first concrete truck backed in for the first pour you couldn't see his tires compacting the stone more than a quarter inch.  That made me feel good about the degree of compaction.  

Another thing.  With mesh the try to pull it up to the middle of the 4" but then they inadvertently step on it later.   Also due to ground prep imperfections your 4" slab is likely to be 3" in some places and 5" in others.     That's one reason I opted for 6".   I also half thought about a lift in the future but it's a remote possibility.  


Put the widest doors on it that will fit.   Especially if it's for her parking.  

Most sidewalks in the area are at least 5". As others said, Thickened edge/ footer and I'd go 6" slab with mesh

Not necessarily, MaxJax only requires a 4" pad for their 6k lb lift (and I think most others are similar).  

MaxJax specs:  
1. Concrete Specifications

   The floor on which the lift is to be installed must be 4-inch minimum thickness concrete
   Must have minimum comprehessive strength of 3,000 PSI
   Must be installed on solid level concrete with no more than 3-degrees of slope


Bendpak is 4" of 2500psi for up to 14k pounds...

I "think" a 36" deep footing is adequate for your area.  It's 24" where I live in VA..  Your local building inspection office can confirm the depth requirement if you don't have a code book.

Another thing that you may want to consider is a course of block on top of the slab to get some clearance between the exterior earth/mulch and siding.  It does two things, limits termite access and helps to reduce decay of the lower courses of siding.

A 4" slab of 4,000 psi mix will support cars in the parking area.  Just make sure the base beneath it is compacted.

That thing will be heaved and not level in no time flat.

Build a pole barn. You take posts and drill holes 36inch down. Build your barn then pour the cement when the building is done.

see
https://www.ar15.com/forums/general/-/5-1591972/?#i45665426

compare:
https://www.ar15.com/forums/general/Just_got_a_quote_for_a_set_of_extremely_simple_garage_plans__ouch_/5-1800678/&page=2#i56286113
and
https://www.ar15.com/forums/general/Just_got_a_quote_for_a_set_of_extremely_simple_garage_plans__ouch_/5-1800678/&page=2#i56290480

Among other things I really like how you built the foundation for your garage.  Came off the footing with CMU well above finish grade to protect the wood structure and it allowed your interior slab to float/move with the temperature fluctuations.  

OP, that's an important consideration for folks in the upper 2/3rds of the country.  The clearance between the siding and earth is a concern for all of the states.

Nothing like fighting a garage door in winter because frost heaved the building out of square.

so what if the garage is heated Would there still be frost heave problems?

Yes

Check building codes for your part of the country. Don't rely on what someone has done in a different state and think it has anything to do with what you are building.

yes.

Yes

Around here we have a 3' frost depth or slightly more.  The building department will still allow a monolithic (thickened edge) slab on a heated structure if it has an engineers stamp and it has to have an insulated perimeter.  Usually 2" or so rigid insulation with 2' run vertically, and 2' run horizontally and away from the building at the bottom of the trench.  

Like a.) In pic below

Attached File

At least within 4' diameter of where the lift posts go.  It doesn't have to be the entire floor but this guy is right.

I wont argue with your specs.... But if you've ever installed one, you'd change your mind on that thickness.   There's not a lot of margin for error in installing the anchors in whats supposed to be 4" crete.

Do you live in area that has a building code?

Are you going to have to pull a permit?

If yes to either of the above, then you need to get with your local building department and find out what they require rather than a bunch of strangers on the internet.  

If not, and you want to avoid having part of the building heave and part not during the winter, then you need to find out what your local frost line is and get below it.  Ours used to be 42".  I haven't poured concrete in quite a few years, but it may be more than that now.

Will the building be attached to a residence or a detached building?  Makes a big difference.  Attached usually requires the same foundation as the dwelling.

Barring that, you want at least rat walls to keep critters from burrowing under and living and possibly undermining your slab.  Around here that means 6" wide by 24" deep.

Edit to add, here is Indiana:





Indiana Residential Code

Page 50 has building foundation depths by county

Page 59 has the info for detached building foundations.  Looks like 8" W × 18" D or 12" W × 12" D for a monolithic slab with wire mesh.