Slab Foundations & Swimming Pools

Two obvious issues regarding pools and slab-on-ground foundations

Pools too close to the slab foundation

This condition is widespread. For reasons that escape me, there are a large number of pool owners who want their pool as close to the house as possible. There is a reason why this is a bad idea. If the edge of the slab is closer to the edge of the pool than the water is deep, the soil might not be able to support the slab foundation as well as it should. Even with that rule of thumb, in my opinion, there should be at least five feet between the slab foundation and the edge of the pool.

Swimming pools leak causing the supporting expansive soil to swell 

Almost all inground swimming pools leak. The pool water can percolate through the gunite pool shell adding moisture to the supporting expansive soil.

The plaster on the gunite shell is intended to prevent leakage through the shell but is less and less effective as time goes on. The large majority of pool homeowners have no idea their inground pool is a threat to their slab foundation.

The pool plumbing is PVC plastic pipe. Most of it is underground, out of sight and out of mind. It is not This pipe is not designed to withstand a pressure load of up to 5000 psf (pounds per square foot)  and, from an engineering perspective, the inground plumbing should be designed for a crushing load in that range. Otherwise, leakage in the in-ground piping is a significant risk.

Pool decks can directly threaten a house foundation 

Pool builders habitually slope the pool deck so that ant water on the deck will not drain toward the pool. If the decking sloped toward the pool, the water would inevitably take dirt and debris into the pool.

Just because pool builders do this, does not make it right. I have no problem with directing water away from the pool, but you cannot offload the water to the soil within 5 feet of the foundation. If you do, you are creating an unnecessary risk of foundation distortion. 

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