In other blogs, I’ve spent considerable time discussing how to distinguish between heave and settlement. Below is a quick primer. For more information, see this blog. Keep in mind that on newer structures, heave will typically manifest first at the edges. Over time, it migrates toward the center, creating a dome-shaped heave pattern.

Below is a depiction of a typical edge settlement.

The section view above manifests with the topo pattern below.

Over time, moisture migrates to the center portions of the structure. See my blog posts.

The above section view will manifest as a topographic pattern below.

As noted earlier, this is a very simplistic review. For more information, please see my previous blogs about floor elevation and soil moisture in foundation inspections.

As shown below, piering to fix expansive soil heave is ill-advised. More on that later. So now that we have recognized heave, what are the available tools to remedy it? Here are a few.

• Cut Off Walls
• Slab Removal and Replacement
• Grading and Drainage Improvements
• Excavation Lowering
• MoistureLevel® Soil Moisture Management System

Let’s explore these!

Cut Off Walls

Cut off walls can be effective in reducing moisture intrusion from outside to under the slab. They are expensive and intrusive/disruptive. What they do is effectively lock in the moisture that already exists under the slab for good or bad. It reduces fluctuations. 

A Variation of this is a horizontal heavy plastic cut off wall. Below are details from David Deatherage PE. 

Slab Removal and Replacement

This is expensive and difficult to pull off constructively in a workmanlike way. It’s usually cheaper to rebuild from the ground up.

Grading and Drainage Improvements

These are almost universally recommended with the direction of an experienced forensic geotechnical engineer. In drier climates, the plan is usually to move the water away from the home with gutters and below-grade hard pipes. In wetter climates, water soaking may be advised or equalizing the moisture around the home. 

These types of repairs can be effective for edge heave but are less effective with dome heave profiles. Below is an example of a typical plan. 

Excavation Lowering

This is the method of using air tools to excavate under existing slabs with the goal of supporting it with piles and lowering it to a more serviceable elevation. It is expensive and intrusive. This is usually more effective with uniform thickness post-tensioned slabs with a smooth under slab profile.  

Below is shown with a cut off wall in addition to the excavation lowering.

MoistureLevel® Soil Moisture Management System

This system was first developed by myself and J. David Deatherage, P.E., in 2015. Dave also authored a white paper documenting its performance. On average, the system removed 62 lbs of moisture per day.

It utilizes active soil depressurization, which is a concept that’s been proven in the environmental engineering field, especially within the radon industry, since the 1980s. It works by moving dry air through the porous sand and gravel layer. 

As the flow of air moves across the surface clay layers directly below it, the top surface of the clay is dried out. Then, as the moisture in the lower layers wicks up to the dried layer, it continues to dry, forcing more wicking from sequentially deeper and deeper layers to 3-5 feet, depending on the soil and moisture characteristics. 

It then utilizes a moisture sensor 24 below the sand/gravel layer to turn the vacuum unit down to a maintenance level when moisture dryness is achieved. 

Expansive soil heave is a topic ignored by the foundation repair industry. Why? Because the industry is largely built by suppliers who cannot make money selling products to installers when providing these products. However, that does not negate the need to provide the right solution for the corresponding problem.

What the industry tells their installers is that you can raise the lower portions of the home to make it more level for a heaving area. While this may achieve a more level floor slab temporarily (that includes risk to infrastructure for raising to a new, unprecedented elevation), the big problem continues to go unaddressed and could easily continue unabated. Clearly, a more sustainable solution is in order.

The solution chosen should suit the particular problem of edge heave vs center heave. Most importantly, the data should guide the correct diagnoses and if the problem indicates expansive soil heave then the solutions should include the methods to address it.