How To Identify and Repair a Sinking Foundation (2024 Guide)
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Your home’s foundation sits on layers of soil that can shift under the weight of the structure. Some shifting and settling is normal, but a sinking foundation is a serious problem you should address immediately. Our guide covers the warning signs and causes of a sinking foundation, plus steps you can take to remedy the situation.
Warning Signs of a Sinking Foundation
Some warning signs of a sinking foundation include cracked drywall, wall gaps, and a leaning chimney. Learn more about these signs and others below.
Cracked Drywall or Floors
The pressure and distortions caused by a sinking foundation can manifest as cracks in your walls and ceilings, often occurring near corners or around doors and windows.
Cracks in your foundation, drywall, and floors are normal as your house ages, but floor or drywall cracks that have the following characteristics warrant further investigation by a foundation inspector:
- Diagonal cracks (45-degree angle)
- Cracks wider than 1/8 inch
- Cracks that are wider at one end than the other
- Horizontal cracks
Gaps Between Walls, Windows, or Cabinets
You may have a bad foundation if you notice your window frames, doorframes, or cabinets pulling away from your walls. There may also be gaps between your wall and chair molding or between the kitchen backsplash and countertop. These fixtures can pull away from the wall and shift when a weak foundation moves and sinks.
Gaps between the floor and wall or between the baseboard and wall could allow moisture and pests inside your home.
Leaning Chimney
You may not notice your chimney leaning when your foundation first starts sinking because it takes years for this structure to shift. However, you’ll eventually see a space between the chimney and your home’s exterior. Moisture can collect in the gap between your chimney and foundation, resulting in mold growth.
Misaligned Doors and Windows
Humidity and temperature changes can cause doors and windows to swell and shrink, making them difficult to operate. However, a sinking foundation or uneven settling could also be the culprit. These issues can put pressure on the frames, causing them to warp or creating gaps. Check for foundation cracks if you suspect a sinking foundation is the cause for your misaligned doors or windows.
Musty Basements
Moisture can enter through tiny cracks in your basement or crawl space when your foundation shifts, leading to rotting wood and mildew growth. Mold can also grow if you have excess moisture in your basement. Exposure to mold over time could affect your health, so it’s important to identify and address the underlying cause of your musty basement as soon as possible.
Protruding Nails
Another sign of a house sinking is protruding nails in your walls, sometimes referring to as “nail pops.” When a structurally unstable foundation shifts, the house’s weight is redistributed, and the extra pressure may cause the wall studs to bend and jut out. If a sinking foundation is behind your nail pops, could see several loose or protruding nails.
Sagging Ceilings or Floors
Floors and ceilings rely on the stability of the walls and beams supported by the foundation. Sinking or uneven settling causes these beams to tilt, twist, or bow, resulting in visible sagging in floors and ceilings. Your floor might develop noticeable dips or slopes in various areas, or you may hear new creaks as you walk around. Similarly, your ceilings might develop dips or appear wavy.
What Causes a Foundation To Sink?
Foundations can sink for several reasons, such as changes in the weather, poor home construction, and soil composition.
Changes in Weather
Extreme temperature and moisture fluctuations can cause foundation problems. Specifically, ice formations can develop under your home when damp soil freezes, expanding and shifting your foundation upward. It’s normal for soil to contract and expand depending on how much water it absorbs, but these freeze-thaw cycles can cause foundation issues if the soil wasn’t compacted or prepared properly.
Natural Disasters
Major flooding events can erode and destabilize the soil around the foundation, causing significant sinking. Seismic activity can also cause sinking. In earthquake-prone areas, even well-constructed foundations can be affected.
Soil Composition
If the soil beneath the foundation wasn’t adequately compacted during construction, it can settle over time, leading to sinking. Sandy soil can compress under the weight of your home, causing a shift in the foundation. Clay soil might dry and shrink or expand and push upward due to drought, broken water lines, improper drainage, or even tree root activity. The soil underneath your home may also shift if a contractor built the house over swampy land.
Poor Construction
The U.S. Department of Housing and Urban Development has outlined foundation requirements that home builders must follow when building a home. Homes built more than 50 years ago may not be up to code, which could result in structural damage over time.
Even if a contractor has built your house to code, its foundation can still shift due to mortar joint structures that absorb moisture.
If the foundation wasn’t designed or built to properly support the weight of the structure, it can eventually sink under the pressure. Improper reinforcement or the use of unsuitable materials can lead to structural weaknesses and eventual sinking.
Failing to install a proper footing is one construction issue that could cause a foundation to sink over time. That’s the problem Mark McCullough uncovered in the video below. Watch him walk host Kevin O’Connor through the problem and his process for adding footings to an existing home:
What To Do About a Sinking Foundation
A contractor may be able to lift your home to make repairs if it’s a mild or moderate home foundation issue. A contractor will cut your house from its foundation and lift it using a hydraulic jack. A wooden, steel, plastic, or concrete crib wall will temporarily support your home while the contractor installs a new foundation or extends the existing one.
More severe foundation problems will be more expensive and likely require a combination of solutions to fix the issue.
Most repair methods involve underpinning, which reinforces an existing foundation. The contractor will lift the house using a hydraulic jack and installs beams, or piers, into the ground, stabilizing the structure.
We’ve listed three piering methods below:
Here are two other options to fix your foundation without underpinning:
Should I Hire a Professional for Foundation Repair?
Foundation repair can be expensive, but tackling this project yourself is risky and could result in further damage. For example, homeowners who try to fix their sinking foundation often use a self-leveling compound or concrete haunches. These temporary fixes can actually cause more sinking.
It’s easier to fix small structural issues in interior walls, such as vertical cracks, by filling them with a resin injection. Exterior walls that line your perimeter sit on concrete and require special tools and expertise that most homeowners don’t have, making them much more difficult to repair.
Our Conclusion
We recommend hiring a foundation repair expert to fix a sinking foundation because most homeowners don’t have the tools or skills to fix it on their own. Enlist a structural engineer to perform a foundation inspection, and obtain multiple quotes before hiring a contractor for the repair. If you need help covering the cost, the federal government does offer a few assistance programs that make home repairs and renovations more affordable.
FAQ About Sinking Foundations
How serious is a sinking foundation?
A sinking foundation isn’t something you should ignore. Your home’s alignment could worsen and compromise the safety and stability of your home if you don’t address the issue immediately.
When should I be worried about foundation settling?
You should be worried about foundation settling if you notice horizontal cracks on your foundation walls, cracks in your floors, foundation cracks at a 45-degree angle, or gaps between your walls and cabinets. You’ll also want to keep an eye on a sinking foundation if one side of the foundation is higher than the other or if you have a leaning chimney.
Do foundation cracks mean my foundation is sinking?
Not necessarily. Although foundation cracks can be a sign of a sinking foundation, they can have other causes. Hairline cracks, for instance, can occur naturally as concrete cures and may not indicate a serious problem.
How much does it cost to fix a sinking foundation?
It generally costs between $2,174 and $7,828 to fix a foundation, with the average cost being approximately $4,998*.
*Cost data via Angi.
Who should I contact first if I suspect a sinking foundation?
If you suspect a sinking foundation, start by contacting a qualified structural engineer. They can accurately diagnose the issue and provide an unbiased recommendation regarding next steps. Avoid relying solely on contractors or general handymen.
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