Sinking Foundation: What It Is and How to Fix It

If your floor feels uneven or doors start sticking, your foundation might be sinking. A sinking foundation isn’t just an eyesore – it can lead to cracks, water leaks, and big repair bills. The good news? You can catch it early and choose fixes that fit your budget.

Why Foundations Sink

Most sinking happens because the soil underneath can’t hold the weight of the house. Here are the common culprits:

• Loose or expansive soil – Clay swells when wet and shrinks when dry, shifting the slab.
• Poor drainage – Water pooling around the base erodes support and causes the ground to settle.
• Tree roots – Roots can pull soil away from the footing, leaving a gap.
• Construction errors – Skipping a proper compaction step or using the wrong mix weakens the base from day one.

Knowing the cause helps you pick the right repair method.

Spotting the Warning Signs

Don’t wait for a big crack to appear. Look for these early clues:

• Uneven floors when you roll a marble across the room.
• Doors and windows that stick or don’t close properly.
• Cracks that run diagonally across walls or around door frames.
• Gaps in the exterior brickwork or between the wall and the foundation.

If you notice any of these, call a foundation specialist right away. Small problems are cheaper to fix.

Do‑It‑Yourself Fixes for Minor Sinks

When the movement is slight, you can try a few low‑cost steps before hiring pros:

1. Improve drainage – Clean gutters, add downspouts, and grade the soil away from the house slope.
2. Install soil anchors – Small steel rods driven into stable ground can give extra support.
3. Use a mudjacking kit – This involves drilling a few holes and pumping a cement slurry to lift the slab back up. Kits are sold at hardware stores, but follow safety tips.

These tricks work best when the soil isn’t overly expansive and the sink is less than an inch.

Professional Repair Options

If the sink is more than a finger’s width or the cracks keep growing, call in the experts. Here are the main methods they use:

• Helical piers – Screw‑in steel shafts that go deep into stable soil. They lift and hold the foundation in place.
• Carbon fibre straps – Lightweight straps attached to the walls to prevent further movement.
• Polyurethane foam injection – A foam expands under the slab, raising it quickly without heavy equipment.
• Traditional concrete piering – Large concrete columns poured below the footings to provide a solid base.

Cost varies: foam lifts can be $5‑$10 per square foot, while helical piers often range $15‑$30 per foot. Get at least three quotes and ask each contractor to explain their approach.

Keeping Your Foundation Healthy

After the repair, stay on top of maintenance:

• Check gutters twice a year and keep the soil graded away from the house.
• Watch for new cracks – a tiny hairline line can become a big problem if ignored.
• Consider a moisture barrier under the slab if you have a crawl space.

Simple habits save you from costly fixes later.

Bottom line: a sinking foundation is a warning sign, not a death sentence. Spot the symptoms early, tighten up drainage, and choose the right repair path. Whether you DIY a small lift or bring in professionals for helical piers, acting fast keeps your home safe and your wallet happier.