Foundations sink for a variety of reasons and a common culprit is excess moisture in the load-bearing strata. For example, after heavy rains the water table rises and saturates the soil that supports the foundation. The soil then swells because it has absorbed moisture. Later, when the soil dries, it shrinks. This expansion followed by contraction followed by expansion again and then contraction – because it’s almost always cyclical due to seasonal weather changes – puts stress on the foundation and can cause major structural damage.
Certain types of soil are more likely to cause foundation problems. Soil with a lot of clay or sand in it is particularly problematic. When you build on top of clay or sand (common in coastal regions) you run the biggest risk of problems with your foundation.
Repair solutions for foundations include push piers, helical piers, and slab piers. Of course, the repair method will vary according to the type of problem.
How to Fix a Sinking Foundation – Underpinning methods
The goal of the underpinning process is to transfer the building’s weight to load bearing strata. This involves driving steel posts deep into the earth until they reach stable material. Hydraulic jacks are then used to raise the structure.
Steel push piers (resistance piers)
Hydraulic pressure and the weight of the structure itself are used to drive steel push piers – also known as resistance piers – deep into the soil until they hit the load bearing strata. Once all piers are driven, a synchronized hydraulic system is used to lift and level the building. Once the jacks are removed, the building continues to be supported by the push piers.
Helical piers
Screw-shaped piers are driven into the soil until they reach load-bearing strata. The bearing capacity of each helical pier directly relates to the torque required to advance them. (Helical piers don’t use the structure’s weight to drive the piles.) After the piers are installed, the same synchronized hydraulic system is used to lift and level the building. Unlike push piers, helical piers are also used to support new construction foundations.
Slab piers
Slab piers can be either steel push piers or helical piers . The difference is they are installed by core drilling small holes in the concrete slab. Anchors are then driven through the holes and down into the soil until they reach load-bearing strata. Steel brackets are then inserted into the holes to secure the anchors to the foundation.
Causes of foundation problems
As we mentioned above, excess moisture is usually the reason for foundation problems. The seasonal changes in moisture content cause expansive soils (explained below) to go through a shrink-swell cycle that creates movement under the foundation. If this goes on for long enough, there will be structural damage.
Things that make a structure susceptible to foundation damage include…
- Expansive soil. Expansive soils with a lot of clay or peat in them cause more foundation problems because they swell and shrink according to seasonal weather changes. The damage happens because this movement in the foundation never happens uniformly. If it did, there wouldn’t be anything to worry about. However, when only one area under the foundation settles, this differential movement can cause significant damage.
- Sandy soil. Sandy soil also causes problems. Although sand doesn’t expand and contract like clay, it can wash away. When this happens gaps form under the foundation and this leads to instability.
- Soil that wasn’t properly prepared or compacted. Soil that has been either disturbed or brought in to use for fill needs to be properly compacted before a foundation is placed on top of it. Fill solid that has organic matter also poses a problem because as the organic matter degrades, it can leave voids leading to settlement or sinkholes.
- Poor drainage around the foundation. As we’ve already pointed out, most foundation problems are caused by moisture. Therefore, make sure there’s good drainage around your foundation. Basements should also be waterproofed. Dramatic seasonal weather changes. As we pointed out above, this is problematic when the soil in your region is expansive. All that shrinking and swelling put stress on a foundation.
- Leaky plumbing under the structure. Leaky plumbing can increase the moisture content in the soil around the building. If the structure is built on expansive soil, this could lead to foundation problems.
- Large tree roots near the structure. Trees take in moisture through their roots. This could cause the soil to dry out, shrink, and become unstable.
- Floods, earthquakes, or droughts. This goes without saying. Floods and droughts cause extreme changes in the soil’s moisture content, and earthquakes, well, you know what they can do to a structure.
Signs of foundation problems
Sinking foundations can cause serious structural damage that could even lead to safety issues if the problem isn’t repaired immediately. If you see any of the following signs, contact a foundation professional right away.
Exterior signs of foundation problems
- Wall rotation. Do your exterior walls seem out of place? If the soil under the house gets saturated with water, the outside edge of the foundation might sink while the inside edge pulls up. When this happens, it causes the wall to rotate in place.
- Separation or cracks around doors, walls, and windows. This is caused by movement in your foundation.
- Stair step cracks. Stair step cracks in brick or cinder block walls – cracks in the mortar between the blocks – are a telltale sign of foundation trouble.
- Steps that are pulling away from the foundation. If you see this, it might be just the foundation under the chimney or porch. However, it could be your home’s foundation.
Interior signs of foundation problems
- Doors and windows that stick. Even small movements in the foundation can cause this.
- Bowed and/or cracked walls, including drywall. While hairline cracks are normal, larger cracks that appear suddenly are a sign of foundation problems. Wallpaper tears as well.
- Floor cracks. Cracks caused by dropping something on the floor are usually localized to one or two tiles at the most. However, cracks that run straight across the floor – wall-to-wall – are an indication that you could have problems with your foundation. Tiles that have lifted up off the floor are another sign of foundation trouble.
- Floors that aren’t even or that bulge. Call a foundation professional if you see uneven, sunken, sloping, or bowed floors. Also, floors that have separated from the wall.
- Moldings that are out of place. Moldings can crack – or even rip away from the walls entirely – when there’s movement in the foundation.
- Wet, moldy crawl spaces. Damp crawl spaces that smell of mold could be a sign that the soil around your foundation is saturated with water.
- Corners of doors and windows cracked. Look for larger cracks that run from the corners of doors and windows up toward the ceiling. Small, hairline cracks probably aren’t a problem.
Read more about Foundation Leveling Methods
Sinking Foundation Repair Cost
The cost of repairing a sinking foundation depends on various factors including your geographical location, the cause and severity of the problem, and the chosen repair solution. Each home’s repair is different and pricing is case by case. Therefore, we can’t give you an exact repair estimate without first inspecting the foundation.
To know how much it will cost to fix your sinking foundation, most foundation companies offer free estimates and inspections for homeowners. Contact us today to schedule your foundation inspection if you live in the Bay Area or Northern California.
Think you might have a sinking foundation?
Yes, trouble with your foundation is serious business. It’s not something you can afford to ignore. The good news though is that foundations don’t need to be rebuilt from scratch. They can be repaired, often quite easily.
If you notice any of the above, contact us today to set up an inspection.
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