Is your contractor going to order a soil report for your site?
I know I keep repeating this, but it makes no sense to underpin a foundation without a soil report. The whole idea is to support the foundation from a deeper, more stable soil. How can you do that without a soil report for your site? The answer is: you can’t.
The lack of a soil report is just the start. The repair contractor may say that you don’t need one, that he or she has experience in the area so a soil report would be a waste of money. Unless he or she has a signed and sealed report from a licensed geotechnical engineer, there is no rational way to engineer a repair.
Will the prospective contractor retain a licensed engineer to design the repair?
In Texas, designing a foundation repair for a foundation in an expansive soil can only be done by a Texas Professional Engineer. Many contractors, large and small, create their own plan and then search for an engineer to seal it. This is arguably a form of illegal plan stamping.
How to cheat using segmented piles
Ask your contractor how he or she will get the pile segments to a depth below the active soil zone. Segmented piles of all kinds are driven using the weight of the slab. Let’s say that the active soil zone is 12-feet below the ground surface. If the piles lift the slab at 8-feet, how do you get the piles to go to the desired depth? I presume that the piles can be jetted in, or maybe not. Jetting is the process of forcing water under pressure around and under the pile to lubricate and/or displace the surrounding soil. Jetting does not always work. Before you sign on that dotted line, your contractor should explain how he knows the target depth and what he is going to do to make sure he can reach it.
A really detestable way to cheat you
In a segmented pile system, all pile segments are placed vertically. As additional segments are added the resistance is from the first segment bearing on the soil and from skin friction for all the segments.
A way to cheat this system is to place the first segment horizontally instead of vertically. This greatly increases the bearing resistance. It also means that the foundation is likely to begin lifting when the piles are at a much shallower depth. This saves money and time.
Abusing the system this way is a virtual guarantee of future problems. The foundation can be made more level this way, but it will not be significantly more stable.
This one is even worse
In this system, a concrete pad is first inserted into the access hole. The pad could be one like you buy at a nursery. The first pile segment is then positioned vertically on top of the pad. Now the bearing resistance is much, much higher. This will result in the foundation being more level to some degree, but it will not be more stable.
How to cheat with bell-bottom piers
The easiest way to cheat using bell-bottom piers is to drill to a shallower depth than what is recommended in the soil report. Drilling to 8 feet when the soil report requires a depth of 10 feet may save the crew time and effort, but you are not getting what you bargained and paid for.