Sinking Foundation: Causes, Warning Signs, and Fixes
If you’ve noticed doors dragging, cracks spreading, or uneven floors, your house might be dealing with a sinking foundation. It’s not just an eyesore – it can lead to serious structural damage if you ignore it. Below we break down why this happens, what to look for, and what to do next.
Why Foundations Sink
Most sinking foundations are the result of soil movement beneath the slab. In the UK, common culprits include clay soils that expand when wet and shrink when dry, poor compaction during construction, and drainage issues that wash away supporting earth. Even a small shift can set a chain reaction of cracks and sloping floors.
Another hidden factor is groundwater. If your property sits near a river or has a high water table, changing water levels can erode the ground that holds the concrete. Sub‑surface work like digging a new garden room or installing a pool can also destabilise the foundation if proper shoring isn’t used.
How to Deal with a Sinking Foundation
First thing – get a clear picture of the problem. Walk around the exterior and interior, measuring cracks with a ruler or a crack‑width gauge. Note any doors that won’t close fully and check if the floor slopes more than 1‑2 mm per metre. These simple checks help the engineer focus on the right spots.
Next, call a qualified structural engineer. They’ll assess soil conditions, the foundation type, and the extent of movement. In many cases the engineer will recommend underpinning – inserting reinforced concrete piers or steel brackets beneath the existing footings to transfer the load to stable ground.
If the issue is water‑related, improving drainage can stop further sinking. Install French drains, extend downspouts away from the house, and make sure the ground slopes at least 5 cm away from the walls. Good drainage not only protects the foundation but also reduces the risk of future cracks.
For minor settlement, a simple grout injection can fill voids and stabilize the soil. This method uses a low‑shrink, high‑strength cement mix that expands slightly as it sets, lifting the slab back into place. It’s a cost‑effective option when only a small area is affected.
Don’t forget to keep an eye on your insurance policy. Some home insurance plans exclude coverage for foundation problems caused by subsidence or poor construction. Knowing what’s covered can save you from unexpected out‑of‑pocket expenses.
Finally, plan your next steps. If underpinning or grout work is recommended, get at least three quotes and ask each contractor about certifications, warranties, and past project references. A reputable builder will explain the process in plain English and give you a realistic timeline.
In short, a sinking foundation isn’t something you can fix with a DIY patch‑up. Spot the signs early, bring in a professional, address water and soil issues, and choose the right repair method. Acting now protects your home’s value and keeps you from living with a sloping floor for years to come.
