Construction Defects - Foundation Cracks
February 27, 2009
Before you can assess the seriousness of your foundation crack, first determine how your home is built. The three basic foundation types are:
Though there are similarities in the issues for each foundation type, each also has some unique considerations.
Concrete Slab on Grade
If your home’s floor is concrete and roughly six to ten inches higher than the landscape around your home, then you have a concrete slab on grade (on dirt). The two places where you may observe cracks are in the:
- Slab floor
- Footing (lower part of the exterior walls.)
When a crack appears in a concrete floor, it’s referred to as a “cracked slab.” Such cracks are seldom noticed because the concrete floor is covered with carpet, tile or some other finished flooring material. The term “cracked slab” has become almost synonymous with ”Run away. Don’t buy this house! It’s about to fall down!” That’s not exactly true, however.
The truth is that hairline cracks in either a concrete slab or footing are common and almost expected. They typically occur when the concrete cures and shrinks, and almost always appear within the first 30 days after the concrete is poured. As long as the crack has the following characteristics, it is of little concern.
- Very narrow
- The same width from one end to the other
- The surface remains flat and even on both sides (no displacement or bulging)
Regardless of the width of the crack, any of the following conditions could be a sign that something more serious is wrong with the foundation or the soil.
- If the crack is wider at one end than the other, then something is causing the concrete to pull apart more at one end.
- If the concrete on one side of the crack is at a different level from the other side (it steps up or down), this also indicates something has moved.
- If the surfaces on opposite sides of the crack are not evenly flat, then the concrete on one side is tilting up or down (or if in a footing wall, pushing in or out). This, too, indicates some sort of movement.
To test for flatness, place an 8-foot level (or other perfect straightedge) on the concrete surface with the level extending four feet on each side of the crack. If the level rocks or if it is raised up above the crack, then the two surfaces on either side of the crack are not evenly flat.
Another indicator of a potentially serious problem is if a crack in the floor only becomes apparent because it starts traversing floor tiles.
Any of the above conditions can indicate soil movement. But just knowing you have soil movement doesn’t pinpoint the source of your problem, because some degree of soil movement is natural and expected almost anywhere. For that reason, foundations are engineered to be of sufficient strength to withstand the expected forces of shifting soil. If soil movement is causing unexpected foundation cracking, then the problem could be any one or more of these:
- The foundation was not designed properly for the ground conditions.
- The soil was not prepared properly for the structure.
- The concrete mixture was not of the proper strength.
- Reinforcing steel was not installed properly.
- Concrete was improperly poured.
Raised Foundation Wall
In some areas of the country, houses are constructed on raised foundation walls with a crawl space under the house. The subfloors are built of wood - usually at a level two or three feet (or higher) above the surrounding landscape. You can usually tell this type of construction because of the regularly spaced air vents all around the foundation. This type of construction may also be called pier and beam because the floor is supported by wooden beams resting on concrete piers.
A raised foundation wall may be built of concrete or concrete block. Cracks in a concrete foundation wall are evaluated similarly to cracks in a concrete footing. (See Concrete Slab on Grade above.) Hairline cracks are of little concern, whereas cracks that are wide, uneven or that show displacement or bulging should be investigated further.
If the foundation is concrete block, a crack may follow the mortar joints in a stair step pattern. Such cracks are not usually caused by shrinkage, and even though thin, may be indicating soil movement and require further evaluation.
Full Basement
In homes with a full basement, the basement walls form the home’s foundation. Since they are constructed of concrete or concrete block, the issues discussed above concerning raised foundation walls apply - hairline cracks are normally not an issue, whereas large, uneven , displaced, or stair-step cracks should be evaluated by a professional.
The unique characteristic of the foundation wall in a full basement, however, is that it is holding back dirt and water from entering the basement. This creates two new issues for evaluating cracks.
- If a crack is allowing water to seep into the basement, remediation is required.
- If a crack runs horizontally (from side to side), you may find the wall is also bulging inward. This might be the result of a one-time event – such as a heavy truck driven very close to the foundation causing the dirt to sink and press inward against the wall. Or it might be the result of some active soil movement.
Either of the above cases requires professional evaluation.
Obtaining an Inspection
Even if the crack you’ve found shows indications of soil movement, the problem may still not be serious. There is a certain degree of displacement that can typically be considered not threatening to the home’s structural integrity, and therefore “tolerable.”
In some cases, unusual drought conditions or excessive water can cause soils - especially clay soils - to expand or contract unevenly, putting pressure on the foundation causing it to shift and crack. However, when the soil returns to its normal and uniform moisture level, the foundation can move back into its original position, causing the crack to close.
If you’re concerned, your first step could be to hire a qualified home inspector to evaluate your foundation. If the crack is nothing to be concerned with, you can ease your mind for a very nominal inspection fee. On the other hand, if it turns out to be more serious, the inspector can help you choose a licensed structural engineer to perform a more detailed evaluation. Based on the engineer’s opinion, you can determine whether you need to turn to your contractor or builder for repairs.
Though you may consider calling a foundation repair company for a “free evaluation and estimate,” keep in mind their job is to sell you their service. The opinion you get may not be exactly unbiased. An impartial home inspector, even though it costs a few dollars, is your best starting point.
One thing to recognize in advance is that if there is a real problem with the soil or foundation, some problems can be extremely expensive to fix. If there is not an easy solution, your contractor or builder will probably be very resistant to admitting there is a problem or running to your rescue. Be sure to ask your engineer for an informal assessment of the type of repair needed and ballpark cost.
If the cost is high and the contractor is resistant, consider speaking to a construction defects attorney to determine the best course of action. Be aware that state laws set time limits for filing construction defect lawsuits, so if you think you need to speak to an attorney, you’re wise to avoid delay.
If you need assistance finding an attorney, please fill out the form at the right.
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