# Raising a Garage



## MichaelZ (May 21, 2013)

Our current garage sits on a slab that is cracked. But worse, the slab sits in our cold clay soil (with some sand under it) so in spring and early summer moisture condenses on it, leaving it wet. Even in the winter it can get very wet if we get a thaw. And it then turns into a rust factory! What I would like to do is raise the garage up and somehow put fill and a new slab over the top. Is this possible? Or perhaps raise the garage up enough to put some sort of insulation and slab or other floor? Any ideas?


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## bignugly (Jul 13, 2011)

Check out "Frost Protected Shallow Foundations". There might be a solution for you there.


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## T-Bone 369 (Jan 18, 2007)

Can it be done - sure. Is it economically feasible - maybe if it's a really nice garage. You would have to remove the anchor bolts from the existing foundation and raise the building using beams and jacks. Then you will need to use cribbing to hold the building up from the outside so you can jackhammer out the slab and pour a new slab. You then re-install the jacks, lower it and re-fasten it to the slab. The raising and lowering stages are not going to be cheap. I know that any good concrete man will also charge you a premium to remove and pour the new slag as they will have a lot of hand work where a machine can not get. 

If the garage is small it might be possible to jack it onto some type of trailer and move it off of the existing slab then move it back afterwards. 

If the garage is sitting on a true foundation you should be able to just jackhammer out the slab and re-pour with a vapor barrier and insulation (probably have to remove some of the fill under the slab to keep the floor height correct. Theoretically if the slab has thickened edges acting as your foundation (which is what commonly done on SOG - Slab On Grade - buildings) and it is in good enough shape you could make saw cuts along the inside perimeter and just remove and re-pour the center of the slab. You would need to pin the new slab to the remaining edge but that is pretty strait forward. 

The other option is to remove the old garage (either tear it down and dispose or do a salvage removal and use the components that are good to rebuilt it after the new slab is in place. You'll loose the roofing, roof sheeting in all likelihood and maybe some of the siding depending on what it is. Trusses and sidewalls can be re-used with not problem as can any fixtures. Once the trusses are off the walls can be removed as a whole if you cut them loose at the corners and then re-stood when you re-build. 

None of those choices are going to be very cheap, unfortunately. Find a good contractor and let them look at it and see what they think. With out seeing the actual structure I am only generalizing and they may have a better solution. In the end it's all about what you want to spend. Just don't trip over a dollar trying to pick up a dime.


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## wharton (Oct 9, 2011)

T-Bone managed to provide you with a review that probably is more comprehensive than one you would get for a few hundred bucks, from a local consulting engineer. Outstanding. The key point to his post is that you need to provide us with a clear picture of the foundation structure, and how you define a "slab". Are the walls bolted to a concrete slab that is continuous and level with the bottom of the wall plate? Does the wooden wall appear to be bolted onto a foundation, and is it possible that the slab was poured after the building was erected? This answer is going to determine if a project like slab replacement is even worth the investment.

Two off the wall ideas may be worth a bit of research in this case. First, controlling for humidity. If the garage was semi-finished inside, with fiberglass insulation in the walls and ceiling, and some type of wall covering like drywall, or even 7/16th chipboard (OSB), the problem could easily, and inexpensively be controlled with a dehumidifier. Secondly, the big issue of slab condensation may be resolved by a thin layer of floor covering that would slightly insulate the slab from the humid air. I'm thinking of some sort of industrial rubber matting. I would experiment with this first by using a large commercial "area rug" style floor mat for a while, and see if it not only stays drier on the surface, but also doesn't create a place for mold to grow underneath. 
I feel your pain on this one. We live in the mountains in Northeastern PA. In the last few decades we have turned into some sort of bizarre rain forest. It's nothing to have 1&1/2 to 2X our historical yearly rainfall average in any given year. Roofs are now getting moldy, even in sunny locations, mushrooms grow in the middle of bright and sunny fields, and keeping structures mold and moisture free is an issue.


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## MichaelZ (May 21, 2013)

I like your idea of industrial rubber matting wharton! That might do the trick. This is a detached old garage, and not a very nice one, but if I could keep the floor dryer I would be happy. Seems like right now it does a great job of rusting my vehicle.

Thanks for the info T-bone 369 and bignugly.


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## wy_white_wolf (Oct 14, 2004)

Can you pour a new floor on top of the old one using insulated concrete? I think it would only have to be about 2" thick.

WWW


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## MichaelZ (May 21, 2013)

wy_white_wolf said:


> Can you pour a new floor on top of the old one using insulated concrete? I think it would only have to be about 2" thick.
> 
> WWW


I would love to do this. Would it work?


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## blooba (Feb 9, 2010)

One major thing to think about if you just pour in 2" of concrete, Do you have the headroom? I raised the floor of a shed once not thinking the few inches would make a difference and i would hit my head on the dang doorway almost every time. If anything is close to head height I would rethink this...lol


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## Rocky Fields (Jan 24, 2007)

If you pour over the cracked slab, the cracks will telegraph through the over-pour.


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## farminghandyman (Mar 4, 2005)

If you have room pour a new slab to the side or back (possibly front,) 

and if you can jack it up you can move it,

I would think to the side or the back and use the old slab for parking on, to work on things that will not fit in the building etc., or if there is room,(height) lean to on to the old slab for some covered space,


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## MichaelZ (May 21, 2013)

farminghandyman said:


> If you have room pour a new slab to the side or back (possibly front,)
> 
> and if you can jack it up you can move it,
> 
> I would think to the side or the back and use the old slab for parking on, to work on things that will not fit in the building etc., or if there is room,(height) lean to on to the old slab for some covered space,


Thanks for that suggestion! It might be possible.


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