I am in the process of purchasing a house with a slab foundation in Texas, and the report from the structural engineer recommends injecting a poly-urethane foam to reduce settlement beneath the house. They say in this area that any house has either already had foundation issues or it will in the future (I think this applies more to houses built before about 2000 or so when they started building foundations in a manner better suited for the soils here).
Is there anything I should consider before purchasing this house and contracting this work? I have requested quotes for this work. If the seller cannot provide credit for this work, I would walk away from the house. Or of course I could walk away now without researching this topic further.
Does anyone have experience with injecting poly-urethane foam for foundation settlement? Did it reduce settlement? Was any further work required at some point afterwards, and how many years later was that?
Also, I think the plumbing company said the sewer line diameter is 9 inches, and current code recommends a larger diameter. When I looked up sewer line diameter information online, I saw that they are typically 4-6 inches. Does anyone know of situations where the sewer line diameter should be larger than 9 inches?
Some of the soil saturation is due to the lack of gutters. I would definitely install gutters and try to learn how to fix any other drainage problems.
Here is a more detailed explanation using information from the report:
The sewer line was replaced several months ago. The foundation was also repaired to add some piers at the same time. The report says there are indications of a long term drain line leak (I guess the engineer is saying the noticeable sewer line replacement is the indication). This leak probably caused the noticeable settlement beneath the bathrooms and kitchen. The soil underneath may have been saturated with water, causing the foundation settlement. The report does not recommend installing structural piers, but it says it is important to strengthen the saturated soils and fill any gaps that may have been created by the leak and repair. This can be accomplished by injecting the foam.
Even if the settlement of the foundation does not reduce to the satisfaction of the client, the supporting soils will be strengthened and the voids will be filled to better support the foundation. It should be noted, that because the poly-urethane foam is a non-structural repair technique, the foundation will continue to experience normal seasonal related movements and will continue to fluctuate with volumetric changes in the soil. If the soils continue to subside, the foundation will subside with it.