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Foundation Soils

How Foundation Soils Affect Residential Foundations

What Is Your Home Sitting On?

The simple answer is "the ground". However, the real answer is a bit more complicated than that.

Soils are composed of different ingredients like sand, silt, loam, and clay. These ingredients determine how soils behave under wet and dry conditions and when they need to support weight.

Soil characteristics have a major effect on the foundations and other structures upon which they're built.

Moisture And Soil

Different soil types are affected by moisture in different ways. Each of these three soils reacts to water differently:

Sandy Soils & Your Foundation

Water passes through sandy soils rather than being absorbed. This fact makes sandy soils very stable. Instead of expanding as they absorb moisture and contracting as they dry out, sandy soils maintain a fairly consistent volume and density.

Because of their stability and good load-bearing qualities, sandy soils are less likely to shift and settle, so they rarely cause foundation problems. Unfortunately, sandy soils are less commonly found than other more problematic soil types.

How Clay Soils Affect Your Foundation

Soils rich in clay and silt have the greatest potential to damage a foundation. Clay absorbs water easily, expanding in volume as it becomes more saturated. So-called "expansive clays" can cause foundations to crack, heave and shift.

When clay soils dry out, they shrink and crack, leaving gaps around a house where water from the next storm can penetrate easily and deeply to repeat the expansion cycle. Clay-rich soils usually cause more foundation damage by expanding than by contracting.

Sandy Loam Soils

Loamy soils are usually a very stable soil that shows little change with the increase or decrease of moisture temperature.

The primary concern with foundations built on loamy soils is erosion. When soils underneath your foundation erode, they may begin to be inappropriate strata for sustaining the weight of a foundation and home structure.

The "Active Zone" Of Foundation Soils

active zone of foundation soils

Illustration of the active zone around and underneath a foundation.

Your home is resting on many different layers of soil, each with different thicknesses and performance characteristics that can affect a house foundation.

These soils have been formed or deposited there over thousands of years -- some by water, some by wind, some by glaciers, and some by the contractor who built your home.

Typically, soil layers gain in stability and load-bearing capacity with depth. The surface layer is made up of organic materials, making it easy for plants and other forms of vegetation to grow.

As you go down, you'll find layers of sand, silt, clay, and loam soils, depending on where you live. Deep below these layers is a layer of bedrock. Bedrock is a layer composed of either rock or very stable, densely packed soils.

The soil you should be most concerned about is known as the active zone immediately around and underneath the house. This soil is most affected by changes in moisture and climate -- and the source of most foundation problems. The active zone may vary from a few feet below the surface to more than 30' below grade, depending on what area of the country you live in.

How Does Foundation Settlement Occur?

Foundation settlement is the movement your foundation experiences when the soil can no longer support the weight of your home. Three of the most common reasons for foundation settlement are drying and shrinking of soil, wetting and softening of soil, and poorly compacted fill soil.

dying and shrinking of soil

1. Drying And Shrinking Of Soil

Foundation soils experience most of their drying and shrinking from two common causes:

Drought: Prolonged dry periods cause soil to dry out. As we know, when clay dries out, it shrinks. Soil shrinkage beneath a foundation has the same effect as soil settling: It usually causes a section of the foundation to crack and settle into the void or hollow area where settlement has occurred.

Maturing Trees: The root system of a tree can be up to twice the size of the tree's canopy. If a tree's branches extend over your home, there's a good chance that they extend under your house as well, drawing moisture up from the soil and causing it to shrink significantly.

wetting and softening of soil

2. Wetting And Softening Of Soil

The soils around your foundation experience wetting and softening primarily for these three reasons:

Heavy Rain & Flood Conditions: As clay soil gets wet, it holds on to water and becomes very soft. This soft soil can be weak, causing the home to shift (or "sink") down into it.

Poor Drainage: If water is allowed to stand or "pond" next to your home, the soil will absorb the water. As it does, the soil can weaken and soften once again.

Plumbing Leaks & Broken Water Lines: When a home's plumbing begins to leak under a slab foundation, the soils underneath can begin to become saturated, weakening their supporting capacity.

poorly compacted fill soil

3. Poorly Compacted Fill Soil

In order to level a site where a foundation will be built, builders sometimes bring in loose soil from another location to fill depressed or hollow areas.

This newly moved "fill" soil is much looser and lighter than the dense, hard-packed virgin soils at the site that haven't been disturbed -- possibly for centuries!

The fill soil brought in by the builder has to be compacted thoroughly before a foundation is built on top of it. If the soil is not compacted well, it may begin to compress underneath the weight of your new home, creating settlement problems that can damage your foundation.

Our Foundation Repair Contractors Proudly Serve MI

As a locally owned and operated foundation repair company, we understand the ways that soils in Michigan affect the homes they surround. Our team of in-house foundation contractors is ready to meet with you to explain what's happening with your foundation -- and how to fix it.

To help you decide, we provide each of our customers with a free, no-obligation foundation repair quote, in writing, before you spend a dime with us. Each quote includes an on-site inspection, a personal consultation, and a detailed proposal on how we can work to fix your problem.

We proudly serve Ann Arbor, Warren, Traverse City, Saginaw, nearby areas such as Flint, Waterford, Bloomfield Hills, Taylor, Petoskey, Troy, Sterling Heights, and the surrounding areas of MI.

Schedule a Free Estimate

Please fill in the information below to setup your FREE INSPECTION! A member of our team will call you to confirm the details and walk you through the process.

Please Note: You must be the Homeowner to receive our Free Estimate. Prospective buyers, renters, and non-homeowners will be charged a $250. fee for the written quote. This fee is payable upon setting the appointment, but will be credited to the final job cost if the work is completed by Foundation Systems of Michigan.

Related Resources

Foundation Problems
Foundation Problems

We specialize in repairing structural foundation problems, and can help homeowners like you fix your damaged foundation.

Settlement Sinking
Settlement Sinking

As foundations settle or are pushed in various directions, cracks in masonry are likely to develop.