Sandy soil (left) and sandy loam soils (middle) expand and contract very little with moisture changes. They can be very reliable when supporting a foundation.
Clay soils (right) expand and shrink in volume dramatically with moisture changes and can cause significant foundation damage.
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:
Because of the constant cycle of wet and dry periods that occur as the weather changes, certain types of soil can expand and contract indefinitely, subjecting your foundation to settling or expansive stresses that often cause damage.
Our team of in-house foundation contractors can get your home back on solid ground! Call us for a free on-site inspection today! We serve Glendale, Scottsdale, Mesa, Phoenix, and many nearby areas in Arizona.
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 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.
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.
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.
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.
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.
The MoistureLevel Smart Foundation System was developed to alleviate problems caused by expansive soil beneath concrete slab foundations. Borrowing from radon mitigation technology, the foundation repair method uses a fan and plastic pipe to create air movement and suction on the under-slab soil. The introduction of outside air on the damp soil causes evaporation of the excess moisture. The newly dried soil reduces the soil expansion and resulting foundation damage.
Cut off walls is one method that has been a standard accepted solution by most local forensic geo-technical engineers. This method involves trenching around the perimeter of the house or building to a depth recommended by the geo-technical engineer. Then a very thick layer of plastic is installed, which is run up along the trench and adhered to the base of the foundation. It is then backfilled with either grout or soil cement.
Depending on the situation and the location of the house, we often use this method, as well as helical piers, to fix failing foundations. Since we've opened our doors in 1988, we have seen the most movement with soils in areas surrounding the valley.
With the proper design on a new construction project, the addition of a cut off wall can allow the structural engineer to reduce the thickness of the concrete and decrease the spacing of the cables on a post tension slab. It can therefore pay for itself with initial costs in addition to providing for a better protection against heave or settlement.
Several years ago one of our clients approached us to solve a particular problem of which no existing solution existed. An existing post-tension slab had experienced a large differential edge heave that was bringing severe damage to the house. A manometer survey indicated that it had as much as 2 ½ inches of floor elevation difference.
Because of the geography and climate in the Greater Phoenix area, heaving is much more prevalent than settlement in a residential setting. Many of the symptoms of a heave are mistakenly misidentified as settlement, resulting in scopes of repair that many times are not consistent with what is really needed.
With over a decade of experience, we have developed and patented a proprietary process for excavation that can level, restore and protect a home or other structure from differential heave.
As a locally owned and operated foundation repair company, we understand the ways that soils in Arizona 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 on-site inspection, before you spend a dime with us. Each inspection includes an on-site inspection, a personal consultation, and a detailed proposal on how we can work to fix your problem.
We proudly serve Glendale, Scottsdale, Mesa, Phoenix, nearby areas such as Scottsdale, Chandler, Sedona, Payson, Flagstaff, Peoria, Prescott, and the entire state of Arizona of AZ.
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.
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.
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.