· by Michael Blair, Nashville's Foundation Repair
Piers transfer a foundation’s load past unstable soil to something that will carry it. Ram Jack’s engineer manual, written by a pier maker for its own driven and helical piles, describes advancing each one until it bears on rock or another suitable bearing stratum. In our judgment they are the right answer for a footing that has genuinely settled and the wrong answer for a shrinkage crack, and our post on which foundation cracks matter goes through how to tell the two apart before anyone quotes you for steel.
What do foundation piers do?
They are driven or screwed down until they reach a bearing layer or the installation force or torque the design calls for, then the foundation is transferred onto them. The Ram Jack manual stops a driven pile when the target force is reached or the structure starts to lift as the pile advances, and a helical pile when it reaches a specified torque. That takes the house off the soil that has been moving. The DOE’s Building America guide to gutters and downspouts warns that expansive soils can put extreme pressure on foundations, and our post on what clay does to a foundation covers how that plays out under houses here.
They can stabilize in place or, sometimes, lift back toward the original position. The manual treats lifting as something done only if required, and says a design professional has to verify any lift so the foundation and the house above it are not overstressed. Lift is not always achievable, and we are wary of any quote that promises it before the floor has been measured.
Push piers and helical piers
Push piers use the weight of the structure to drive steel sections down, so they need a heavy structure above them. The Ram Jack manual says its driven piles use the building as the reaction force, typically need a wall load of at least 700 pounds per linear foot, and should not go under light structures such as carports, wing walls, light porches or interior floor slabs. Helical piers are screwed in with torque, and the manual uses that installation torque to verify their capacity. Because they do not depend on the weight of the house to go in, they can be used where a structure is too light for push piers, and the same manual also lists them for underpinning foundations that need to carry heavier loads. Either way the piles go in one at a time, with the load taken off each one before the next is installed.
Both are legitimate. Which suits a job depends on the weight of the structure and the soil, and the manual leaves pile locations and installation criteria to a design professional working from the foundation investigation. A contractor should be able to explain the choice in those terms. Our post on how push and helical piers work follows the installation step by step, and our pier and settlement repair page covers how we take the job on.
- Piers: for genuine settlement of the footing
- Wall anchors or carbon fiber: for bowing walls under lateral pressure
- Crack injection: we use it to seal a crack against water once movement is ruled out
- Drainage and grading: for a common cause, water collecting against the foundation
- Slab jacking: we use it on slabs, not on footings
Bowing walls need something different
A wall pushed inward by soil pressure is not settling. The 2018 Tennessee edition of the residential code sizes and reinforces basement walls by soil class and lateral soil load, a sideways load rather than the downward one a pier is built to carry, and the Ram Jack manual says its driven piles are typically used only in compression. So push piers resist downward load, not sideways push. Ram Jack’s carbon fiber support page describes its straps as made to hold walls that have fractured or bowed from soil pressure or water damage, and the manual lists helical piles in tension as tiebacks for basement walls. How far the wall has moved decides which it gets, and our post on bowing basement walls covers how we measure that.
Water is what keeps adding to that pressure. The DOE’s Building America guide to footing drains says saturated soil can overwhelm the water-sealing on a foundation and recommends a footing drain to carry water away from it. Whatever holds the wall, we correct the drainage and grading alongside it, because a strapped or anchored wall with the same wet soil behind it is still carrying the same load.
Why get an engineer’s opinion before foundation repair?
The diagnosis decides the repair, and the repair decides the price. An independent structural engineer’s report gives you a defined scope to quote against, and an engineer is the kind of design professional the Ram Jack manual expects to place piers and sign off on any lift.
It also lets you compare contractors on the same defined scope, rather than on three different descriptions of what is wrong. If you want the floor levels measured first, our inspection and report starts there, and when you have a scope in hand, ask us for a free estimate.
Sources
- Ram Jack (Gregory Enterprises), Ram Jack Engineer Manual v1.1.1 (July 2023) — Piles advanced to a bearing stratum; stop at target force, uplift or specified torque; lift only if required and verified by a design professional; driven piles use the structure as reaction, about 700 lb per linear foot minimum, not for light structures; torque verifies helical capacity; helical for heavier loads and tiebacks; driven piles in compression; piles installed one at a time; locations from a design professional
- Ram Jack, Carbon Fiber Support — Carbon fiber straps for walls fractured or bowed by soil pressure or water damage
- Tennessee Residential Code 2018, Chapter 4 Foundations (UpCodes) — Foundation walls designed by soil class and lateral soil load
- U.S. Department of Energy, Building America Solution Center, Footing Drain Pipe (updated 2017) — Saturated soil can overwhelm water-sealing on a foundation; a footing drain carries water away
- U.S. Department of Energy, Building America Solution Center, Gutters and Downspouts (updated 2021) — Expansive soils can put extreme pressure on foundations
FAQ
Foundation Piers and What They Actually Fix — questions
How much does foundation repair cost in Nashville?
We would not put a number on it without seeing the house, because the price follows the method, the number of piers, the digging and access, and whatever drainage work goes with it. That spread is exactly why an independent engineer’s assessment first is worth it: it defines the scope, so the quotes you collect are for the same work.
Will piers lift my house back to level?
Sometimes partly, and sometimes not at all. Stabilizing the foundation where it sits, with no lift, is a standard option, and any lift has to be checked by a design professional so the foundation and the house above it are not overstressed. A contractor promising a full return to the original level should be asked what happens if the structure will not take it.
Does foundation repair affect resale?
We cannot speak for every buyer or lender. What we tell owners is to keep the record together: the engineer’s report, the scope of the repair, the floor measurements before and after, and the warranty, including whether it transfers to a new owner. A repair with that paperwork gives a buyer answers, and visible symptoms with none give them questions.
How does foundation repair work?
It starts with a diagnosis, because the cause decides the repair. Piers carry a footing that has genuinely settled, carbon fiber straps or wall anchors hold a bowing wall, crack injection seals a crack against water once movement is ruled out, and slab jacking is for slabs. Drainage and grading deal with a common cause, water collecting against the foundation.