thick pad vs frost wall foundation

[grainger12002]

Anyone have success witha pad floor instead of the conventional 4' frost wall and floor on their building ? We are doing a small barn 36 by 24 and getting mixed sugestions....

In new wngland it gets cold, my thoughts are for a full foundation but wow,the cost....


Thanks

 

[oldnslo]

Floating slabs are allowed for garages, etc in this area. Are you going to have water lines running into this barn? If yes how much movement will they with stand before breaking? I have no idea how much a building that size will move but my garage moved enough to cause the conduit going to the main electrical panel panel to move over 1/4 inch.

NOTE: This is a 4 inch thick pad on a 24' by 30' building.

Roy

 

[BeezFun]

Anyone have success witha pad floor instead of the conventional 4' frost wall and floor on their building ?
Thanks

There was a pretty long thread on this a few months ago, you might search for it. You could search for "floating slab" "frost proof foundation", etc and you should find it. I don't think you've given enough information to help with your decision. I built a 20x30 building about 30 years ago on a thickened slab and it's fine, but it only has power going to it. The slab was an engineered design that specified thickening around the edges, done in one pour. But if you plan to heat the building, or run other utilities into it, you'd have to put some more work into the design.

 

[dodge man]

I have a gargage that is 28'x30' built on a floating slab. It has a thickened edge which is often called a rat wall. Mine is about 12 years old and so far, its been good.

 

[bp fick]

Our frost depth and foundation requirements are likely similar.

We have two choices. First, to set the footer below the frost line, which is 60" and block or pour up from that. We can also set pole barn poles if the depth is also 60"

But, we can also do a floating, monolithic pour pad with rat walls. Rat walls are merely 6" wide perimeter trench and 30" deep to prevent tunneling. We even hand dig them with a "rat wall shovel" so-called. Forms are set up and the pad and rat walls are poured at one time.

The building does indeed "float". Thus, it must be free standing. If one attached a floating building to a 5 foot deep, below the frost line foundation building, the two would not survive the differential of one heaving while the other did not. Hope that helps.

I have no particular preference. They both "work" just fine. My house has a basement with footers down 7 feet, while my shop "floats" and the rat wall is down 36" and then two courses of block. I'm sure you've checked with local authorities concerning which is allowed and which is preferred.

 

[Luremaker]

My shop is 40 x 60 and built on a floating slab. Perimeter of the slab is 18" thick and the floor is 6" thick. I have 5/8" re-bar every foot in both directions and every 6" in the perimeter. I also put 2" (~R10) of polystyrene insulation around the entire building to a depth of 2' right against the slab. Built in 2003 and have no problems. I do heat my shop in the winter. As a added bonus the water drainage around here is great. I never have standing water no mater how much rain we receive. Ground with lots of moister will heave when it freezes, dry ground not so much. I will be building another 40 x 60 shop this coming spring and have yet to decide on pole or slab construction.

 

[Egon]

It all depends on the type of soil and the moisture available.:thumbsup:

If you get frost heaves don't matter about thickness and rebar. It will lift.:thumbsup:

 

[grainger12002]

we do have frost,lots of it,it gets quite cold in the winter in CT. I have heard that the monolithic slab is fairly reliable, I just dont want to end up with a big crack in 4-5 years...

The framer said either method is acceptable and should hold up,just wlooking for some direction

Thanks !!

 

[pnhd65]

I've done both a floating slab, and what's called a 'Rubble Trench' foundation.

You can look that up, but it's basically a footer trench, filled with stone, such as 2B, has a drain line in the bottom to either daylight or a stone filled sump.
And then a footer or thickened edge slab poured on top.

Any way, good luck on your project. :thumbsup:

 

[slowzuki]

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.

 

[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.