RESISTANCE PIERS, HELICAL PIERS, COMPACTION GROUTING OR CAISSONS - WHICH IS BEST?
There is no easy answer that applies to all applications. Each situation needs to be examined individually by a professional foundation repair contractor. Some contractors will have biases to one method over another because they only perform one type of service.
RESISTANCE or PUSH piers typically have the best lifting potential. This is because these types of piers are "pushed" down into the ground, through the inadequate soil until they hit a hard surface - load bearing stratum. The weight of the structure is used as a counter-force to hydraulically push these piers into the ground. Once they hit this bottom, they can be pushed even further so that they actually lift the structure back to their original level. Once that is accomplished, the pier is capped off and permanently attached to the bottom of the foundation. This should prevent any further settling of the structure. The advantage of this type of pier is that a soils report is not really necessary to know how deep the piers must be pushed. It becomes self-evident. Once the "bottom" is reached, that is, stratum that is strong enough to support the structure, the structure can be lifted. These types of piers are typically used for heavier structures but are also perfect for single story residential homes.
HELICAL piers are typically used to support a structure and not to lift it. These types of piers are "turned" into the ground much like a corkscrew. Each pier has one or more "flights" that are like blades that do the pulling into the ground. These flights keep the pier in place after installed. The advantage of a helical pier is that is can be used on very light structures, unlike resistance piers, like a porch. However, to install a helical pier properly, a soils test should be performed by a geotechnical engineer to determine how far down the soil is sturdy enough to support the structure. After all, if you turn a helical into loose soil, it loses most of its holding strength.
Helical piers are very useful in other applications such as tie-backs. Since they are screwed into the ground, and held in place with their flights, not only can they support downward pressure, but then can support an equal amount of outward force. In other words, they can hold things into the ground such as retaining walls. Helical piers are ideal in pre-construction applications. They are installed before the foundation is placed to prevent any future foundation settlement. Also, helical piers can be used in conjunction with resistance piers on hillside homes to lift the structure and keep in place on the hillside.
CONCRETE CAISSONS are typically used in pre-construction for very heavy structures, and as support on failed foundation when lifting is not necessary.
COMPACTION GROUTING is a completely different method of addressing foundation failure. There is no actual contact with the foundation in this method. A very think concrete slurry is pumped under the ground, under the structure creating a "bubble" which then compacts all the loose soil in the adjacent areas. With enough material, this bubble can actually lift the structure back up. However, soil tests by an engineer are absolutely required to determine if the cause is loose soil and where those areas are. Also, only the most experienced companies are capable of performing compaction grouting to lift a structure back without causing damage.
Up-Rite Foundation will be able to help you identify the source of your foundation failure.
| 
