For those not familiar with Colorado soils, learning about the expansive bentonite under some homes can be alarming at first. Buyers should know that settling for homes is not uncommon, and the amount of bentonite can vary from property to property. There are several things that can be done to minimize the effects of the soil on the structure.
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| Floating Wall Detail |
Builders will do tests for each lot they plan to build on, and make decisions regarding the treatment of the soil and the strategy for building. For instance, basements may be completed with a structural floor, meaning that there is a gap between the floor and the earth to allow the soil to expand. For homes with a poured concrete slab, the interior framing can be constructed with "floating walls." The bottom of these walls will include a bottom base plate and a top base plate. The bottom base plate is secured to the floor; the top base plate is attached to the wall framing and the ceiling above. The two plates are "connected" by large nails, which are really only connected to the bottom base plate. The top plate is allowed to float, using the nail as a guide rod should the floor rise slightly.
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| Mudjacking pumps a slurry under the concrete to raise it |
To minimize settling of your home, driveway or sidewalk, make sure there is adequate drainage away from the structure. If there has been sinking of the concrete flatwork, repouring or mudjacking is a way to restore the feature once the cause has been identified and remedied. Properly installed gutters are an important part of protecting the foundation and the concrete. Provided it doesn't interfere with a walkway, downspouts should be extended out at least 6 feet. Proper grading around the home is crucial to drain water away from the home. The soil around the foundation should ideally drop 2-3 inches for every 10 feet away from the structure. Even with these measures, know that extremely wet seasons can still cause some movement despite reasonable corrections.
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| A wide, diagonal offset crack |
Every house is going to settle some, so it's good to know what is normal and what is problematic. Common settlement cracks usually occur during the first year after a home is constructed. Small cracks in the foundation with no evidence of movement of the structure itself is not typically a concern. But cracks larger than 1/4", vertical or slightly diagonal cracks that are wider at the top than the bottom, cracks that show an offset, or many small cracks could indicate a bigger issue. Take a step back and look at your house from the street - do you see any leaning?
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| Common shrinkage crack |
Shrinkage cracks are caused by the natural curing of concrete. They may be wider at the top than the bottom, but are usually hairline width. Small cracks that stop at the top of the foundation and do not continue into the structure are probably nothing to worry about. However, you may want to seal these cracks with epoxy to reduce the possibility of water leakage. A large horizontal crack in a foundation can indicate that the wall is failing to hold back the surrounding soil, especially if bowing is evident. This is more common in a cinder block structure than poured concrete.
Sometimes if all or most of the living spaces are completely finished, it can be more difficult to assess the hidden structure underneath. Drywall cracks are not always a concern beyond cosmetics, and the size and placement can give you some idea of what may be going on. Small cracks at the corners of doorways and windows are common as they are a point of vulnerability in the drywall. Also, a straight line crack that follows a seam in the wall may not be serious, unless the crack widens or there is an offset. Diagonal cracks or those larger than 1/4" may indicate structural movement and should be investigated.
I often see homes with sagging floors. Usually, a little sagging in the middle of the floor is not a concern, but sagging near an outside wall can indicate a more serious problem. It may have something to do with rotting of the floor joists, or if may be that a footing is sinking. If you don't have experience examining issues like this, or you can't see the underlying structure, it's recommended to have a structural professional come out and assess your situation. Give me a call if you need any recommendations!
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