thick pad vs frost wall foundation

[mike69440]

There is another option, you can pour a frost protected slab. Most common way is to put styrofoam under the slab, can also use a non-frost suceptible fill like clean crush to build up a pad.

I built my shop with thickened edge on a rubble trench style. It was meant to be heated but went through the first winter as a bare slab, no building on top. Didn't move at all.

Agree, I'd do both

Floating Slabs work, if ther is uniform drainage under the slab and chrushed stone, drainage sand, etc and foam as a cushion. Rebar the perimeter. The idea is the whole thing floats.

 

[CalG]

It takes two things to heave ground

Water, and freezing temps in the ground.

Stop either, and you will have no issues with movement.

I have two additions on my home here in Vt. Both on rubble trenches with drains to daylight.
Both are single pour slabs on grade with wire mesh to hold the Pex tube. (no joints) (Rebar just keeps the broken pieces from moving to far away when the slab does crack"

The latest work has rigid foam under it with cork tile finish floor, the first , just gravel under, with cermaic tile and stone finish.
I hardly need to heat either even on the coldest winter days.

I've got had my mind on a slab for a car garage, but the spot is very wet. I
need to come to grips with that water problem before I put concrete on top. Non heated and all. I'm thinking trench and fill all around, plus pilings and grade beam. A REAL floating slab ;-)

 

[Egon]

It takes two things to heave ground

Water, and freezing temps in the ground./QUOTE]

You also need ground material that will support capiliary action.

 

[PAfarmer]

I use 6 inches of 3500 PSI N.Y. State highway grade concrete in all of my building with little to no issues. One of these building is closing in 25 years old. I live in Northern , PA........Cold winters and plenty of water..........frost wall construction is really a good option if you plan on having water , plumbing etc in the building where movement is a bigger issue. Your application is really what needs to be considered when choosing construction methods. Remember there are only two kinds of concrete, The one that cracked and the one thats going to crack. Good luck. If you need more help or have any additional questions i would be happy to help. Poured concrete for close to 30 years now. Someone who does excellent site Preparation is where the time needs to be spent and where the money needs to be invested to turn out a decent lasting project. My .02

 

[GE222]

I had a building built, 42' x48' x 14' on a floating slab. The perimeter was around 18" with a floor thickness around 5-6". This was 8 years ago. It is in Southern Wisconsin which can get some rough winters. To date there has not been any issues. I made sure that the building was also well above grade with the top of the slab about 10-12" high. It is unheated and has only electric. To this day if I had to do it over, I still would not install a frost wall. My only real dislike of a frost wall is the added cost which is considerable. I had the advantage in that the base is heavy clay and rock.

 

[slowzuki]

"Frost" wall is kind of a misnomer, it does nothing against frost. People get hung up on the naming of it. In an unheated building ad-freezing can grab that deep footing and toss it around too.

I wasn't keen on filling the ground up with expensive concrete.