In earlier blogs, I discuss soil types, foundation types, and other key factors to help diagnose foundation problems. Now, once we have diagnosed the problem, we can explore solutions. Here are the top effective methods to fix settlement. First, we’ll examine solutions for foundation settlement, followed by solutions for heave.

Foundation Settlement

Helical Piles

A common tool used to fix foundation settlement is helical piles. These are steel shafts available in both solid square and hollow round steel tube forms, with various segmented lengths. In residential applications, they typically range from 5 to 7 feet long and feature one or more helixes near the bottom. 

When properly manufactured, the leading and trailing edges must be parallel. This ensures that as the pile rotates through the soil, it cuts and slices cleanly without auguring or excessively disturbing the surrounding soil. See below.

This cutting through the soil means that the friction generated as the pile slices through the soil can be measured by the torque required to twist it. Since this friction is directly related to the strength of the soil, we can approximate the final bearing capacity of the helix (or helices) using torque measurements.

As a result, by measuring the torque, we can determine the bearing capacity of the pile through torque correlation coefficients. According to the ICC (International Code Council), these coefficients are standardized for all soil types based on shaft size, as shaft size influences torque friction. These standards are outlined in AC 358 (ICC Acceptance Criteria).

• Torque Factor
  • 10             Square bars and 2 3/8” diameter shafts
  • 9                2 7/8” diameter round shaft
  • 7                3 ½”     diameter round shaft

There are larger sizes but they would rarely be used in residential applications. The formula for calculating bearing capacity is:

Bearing Capacity = Torque Factor X Torque (required to twist)

For example:

50,000lbs = 10 (top value for square and 2 3/8”) X 5000 lbs of force to twist

These torque values are conservative values that can be relied on in pretty much all soil types. If a load test is performed by pulling or pushing on the pile with a known force after it is installed on a particular site, it may reveal higher torque correlation coefficients. This would allow for an increased bearing capacity at that location. However, load tests are not typically performed on residential projects.

Helical piles have a number of advantages, including quick installation, no soil spoils, the ability to determine load capacity in real-time, and the ease of driving them with small equipment, such as a compact tractor.

However, they struggle in rocky/cobbley (3”-12” diameter rock) soils.

In residential applications, installers typically use a side-loading retrofit bracket, which introduces an eccentric load. To counter this, an additional steel sleeve is added to the upper 4–5 feet of the pile to resist the eccentric load. Piles are usually driven to refusal to bypass softer, problematic soils.

Good systems have evaluation reports from either ICC or IAPMO and can be looked up on their websites.

Most major manufacturers can be found on Helical Pile World.

In a later blog, I will go into more detail on detailed inspection points for proper installation.

Push Pile

Push piles or hydraulically driven piles are round hollow steel shafts that are pushed into the soil with hydraulic cylinders. These hydraulic cylinders are similar to ones used in everyday tractors.  See below.

These piles are manufactured with various bracket configurations, allowing the weight of the house to push against them as the shaft is driven into the ground.

Similar to helical piles, the force required for installation is measured and used to determine the bearing capacity at refusal, ensuring problematic soils are bypassed. However, these piles require even less equipment for installation compared to helical piles. (essentially a small lawn mower sized hydraulic pump)

They typically feature a friction ring at the bottom, which helps reduce shaft friction, allowing the pile to rely primarily on end-bearing capacity.

Like helical piles, they come with evaluation reports from ICC and IAPMO for verification.

Concrete Push-Type Variation

A variation of the steel shafts are concrete pile segments, usually about 12”  long and 6” in diameter, that are stacked and driven into the soil directly under the footing without a side bracket. Most use a steel cable down the center to maintain vertical alignment. These piles don’t perform well in harder soils.

Micro Pile

Rarely used in residential applications, micro piles are another tool used to overcome the limitations of rocky soils that stop helical and push piles. A common type is hollow bar piles, which are hammered and twisted into the ground while grout is injected and percussively driven to a predetermined depth as the pile is drills through soil and rock.

However, micro piles require larger, more expensive equipment and significantly greater skill to install. Unlike other pile types, micro piles rely on skin friction and therefore cannot be calculated by the force used to drive them. 

Instead, a geotechnical engineer must evaluate the site-specific soil conditions and friction between the grout and surrounding soil to estimate their load-bearing capacity.

Below is a part of a spreadsheet used to estimate bearing capacity for a micro pile:

Compaction Grouting

Compaction Grouting is an excellent tool but a less commonly used technique, primarily due to the high initial equipment costs and the lack of national distributors promoting the process. 

It is done by driving a hollow steel tube down to a predetermined depth. The tip is then knocked out, and then stiff cement grout is pumped with a high-pressure grout pump, down to the bottom until grout refusal occurs. Then, the pipe is raised 12’-36”, and more grout is injected until refusal. The process is repeated until the pipe bottoms near the surface.

The Geo-Institute embarked on a massive research program that resulted in publishing the Consensus Grout Handbook. 

The key concept is the material properties of the grout. It must be loose enough to pump, yet more importantly, stiff enough to not travel once injected into the soil under high pressure. Instead, it needs to stay in a round bulb that displaces the soil, compacting and densifying it. Done in a grid pattern, it compacts the soil between the grout columns.

The depth of the pipe can be based on refusal to drive the pipe. This can be dangerous as it could terminate on top of a rock with soft soil under it that could be overloaded with the weight of the grout column on top of it. For this reason, more data is usually required to avoid this problem.

One key advantage of this repair method is that it simultaneously lifts the footings, floor slab, surrounding soil, and even plumbing and electrical lines, ensuring a uniform elevation correction. The materials are fairly cheap, but the equipment can be somewhat expensive.

The disadvantage of this work is that the process is messy. Cleanup is difficult and time-consuming.

Regardless of whether piles or compaction grouting is used, they must be installed deep enough to reach beyond the active zone—a soil layer that remains unaffected by water fluctuations. If the piles or grout do not extend deep enough, settlement could still occur after the work is completed.

Mud Jacking and Polyurethane Injection

Mud Jacking is done to raise sidewalks, driveways and slabs. This method involves coring 2-inch holes into the slab and injecting grout directly beneath it, lifting the slab through the pressure of the injected material.

A more modern approach is to drill small 3/8” holes in the slab followed by injection of expanding polyurethane grout.

Both methods work well as slab lifting. However, neither method improves the soil and does nothing to stop future movement. Slabs don’t have a lot of weight on them, so this may not be a crucial factor. Also, if there are elevation differences that are a result of expansive soil heave, raising the low slab may not be a long-term solution, as heaving could easily continue and be the cause of much more destructive damage.

Most of the problems with soil-caused foundation movement are the result of changes in moisture. If the soil in the local conditions has been wet or dry, the goal is to keep it that way. 

• In drier climates, the goals revolve around drainage improvement. Getting water away from the foundation. Gutters, drain lines, proper slopes, and avoiding planters that trap water. 
• In wetter climates, the goal is to ensure that the perimeters stay equally moist to avoid drying out.

Grading and drainage should be the first line of defense and can usually be done cheaply by landscapers or even self-performing homeowners. The key is to get the right plan from an experienced geotechnical engineer.

Since the American Concrete Institute (ACI)  has shown that the new slabs regularly are out of level by as much as 1.5”, the current floor levels may not show movement all by themselves. Because of this, professionals often recommend monitoring the home for 6 to 12 months before taking corrective action. Tracking movement over time helps determine whether foundation movement is ongoing or stabilizing, making monitoring a common first step in professional evaluations.

Key Takeaway: Top Methods to Fix Settlement

Experienced contractors can offer more than one solution that fits the needs of the situation to avoid putting round pegs in square holes.  Most of these solutions should be overseen by special inspectors who are licensed professional engineers. Preferably the engineer who diagnosed the problems and designed the solution to fix it. Later, we can discuss how to design the pier configuration to address specific settlement problems as well as solutions for expansive soil heave.