Concrete patio and clay soil: preventing cracks

Jun 21, 2005 3 Replies

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Marty 21 years ago

We live in Northen California north of San Francisco. Our temperatures range from the 30's at night in the winter to the 70's and

80's in the summer with occasional periods of 90's. Our rainfall ranges from not a drop of moisture for months to constant daily rain for months. Our soil is pure clay with tons of shrinkage and expansion. And we've got earth movement from the occasional tremor (earthquake-style).

Is there such a thing as a concrete patio that won't crack and split over time? What's the best preparation that will minimize cracking and shifting given the conditions described above?

Thanks

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barry 21 years ago

No. Concrete is capable of enormously greater compressive than tensile stress. Reinforcing steel is used for tensile strength, which will have to cope with potentially large stresses.

It will crack, especially thin, large-area slabs. That's why tools are used to make "parting lines" in slab, on pouring- to locate where the cracks will be.

Properly dimensioned, supported, and drained below, problems will be minimized. Quality of materials and workmanship are important, obviously.

HTH, J

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Joseph Meehan 21 years ago

Sure but it is expensive.

Good foundation lots of rebar and concrete. Normally the problem is approached by directing where it will crack with intentional weak spots cut or formed into the concrete.

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Goedjn 21 years ago

Set a pair of huge concrete beams one way, and truck in pre-stressed concrete planks to drop over them the other way.

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