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post tension slabs


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Im an appraiser in the Phoenix area. Did a 5 year old home the other day where expansive soil had pushed up the walkway concrete all the way to the door up along the concrete seam a good inch or so. The line led straight to the front door where the "step up" into the house had a small vertical crack. The slab under the house is post tension while the walkway is just poured concrete....Do I need to be concerned about the expansive soil continuing along that straight line?? and pushing up the flooring inside the house??? Just wondering if a post tension slab "beats" expansive soil?? The windows and doors had no sticking issues and there were no other notable cracks anywhere(walls, stucco, etc.) Thanks.

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Small vertical cracks are not generally a concern and can usually be classed as drying a curing cracks.

If no other settlement issues inside the house I would feel okay with the sidewalk problems not being associated with a foundation problem and would note them as a possible trip hazard.

I live in an area of expansive clay soils in North Texas and see upheaval of the sidewalks and drives that do not reflect on the integrity of the foundation. You are looking at unsupported 4 inch concrete that probably has 4 inch square wire for strength versus a foundation that should have grade beams and steel cables.

The post-tension design of a foundation can be "defeated" by the expansive clay soils if proper drainage and foundation maintenance is not addressed. Post-tensioned cable systems were designed for expansive soils and allows for more movement tolerance and flex, but, I still see problems for foundations with post-tensioned cable when the drainage and maintenance issues are not addressed.


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