Expansion Material Needed Or Not?

davidchomes

Hello.

When I have had garage slabs poured the Contractors have told me that expansion material is not normally used or needed when pouring a garage slab inside of block. I have always thought otherwise but they are the experts. On the project that I have in process now, there is a 19' x 16' slab poured inside a block foundation between the house and garage with two of the sides being outside walls. Those outside walls have a crack between the top and second course of block in the foundation. I am thinking that its because of the expansion/ contraction of the slab. Should slabs poured inside of block foundations/walls have expansion material at the perimeter? Also should it be used between the garage slab and garage door apron and between the apron and driveway? How about anywhere that outside flat work abuts the foundation? I am located in Central Indiana where we have some pretty good freeze thaw cycles.

Thanks for your input.

Dave

concretemasonry

Dave -

The slab in the garage will only shrink and will not expand. A joint with "expansion" material is not neded.

Due to the curing shrinkage of the concrete, you can expect cracks in the slab. Sawing joints within 24 hours of pouring will allow you to control where the cracks occur. After the concrete is cured, you can caulk the joints to make it ready for the NASCAR approved epoxy floor coating.

Dick

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Dick

Engineer, designer and consultant recently active domestically and internationally on construction and design in about 35 countries.

CaliDesigns

I put foam expansion material in my garages. Expansion material is to allow for movement, horizontal and vertical. Frost puts load on the concrete from the bottom and will cause it to rise in the winter. Your vehicle will put load on it causing it to move downward. It doen't need to move much to cause a crack. I never like to have my concrete bound between fixed object. It has been worth to me to do this. Less cracks and less complaints.

davidchomes

That is what I always understood but I can't think of anything else that would cause the whole top row of block to be cracked unless it heaved and pulled the block with it.

I did do that. Thanks for your input

Dave

davidchomes

I think that I may just start doing that. For years I have thought that it made sense to do so. What thickness of foam do you use?

Thanks

Dave

CaliDesigns

1/2" Sonoflex

davidchomes

Thank you

Dave