Sagging Floor
A noticeable dip or slope in the floor, where furniture rocks or a ball rolls to one side of the room.
What Is Causing This?
- 1Rotting floor joists due to damp or woodworm
- 2Undersized joists for the span
- 3Subsidence or foundation movement beneath
How Urgent Is This?
This needs prompt attention. Delaying could cause further damage, safety risks, or significantly higher repair costs.
What Needs to Be Done
A builder will lift the floor covering, inspect the joists and supporting structure, and replace or sister damaged timbers. Subfloor ventilation may also need improving.
How Much Will It Cost?
National average estimate
Labour: £3,325 – £8,250 | Materials: £2,300 – £6,700
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Prices are estimates based on typical UK rates. Actual costs depend on the specific issue, accessibility, and your location. All quotes from tradespeople on Tradesfolk are completely free.
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Ask a QuestionPlanning Permission Guidance
Some fixes for this problem may require planning permission or building regulations approval. Check if your project needs permission:
Generally permitted under Part 1, Class A of the GPDO. Standard permitted development allows a maximum projection of 3m ...
Garage ConversionGenerally permitted as an internal alteration that does not enlarge the building. Replacing the garage door with a windo...
Basement ConversionInternal works to convert an existing basement or cellar are generally permitted as internal alterations. However, excav...
How to Prevent This
Ensure underfloor ventilation is not blocked by garden soil or paving. Treat any woodworm promptly. Fix leaks quickly to prevent timber rot.
Related Problems
Floorboards that creak or squeak when walked on, especially noticeable at night.
Diagonal cracks appearing around windows and doors, doors sticking, and visible sinking on one side of the building.
Cracks visible in the foundation walls or signs of foundation movement such as doors sticking and walls cracking.
Other Builder Problems
A visible crack running through the outside wall of your property, which may be widening over time.
An exterior or interior wall that bulges or leans outward, visible when looking along its length.
Diagonal cracks appearing around windows and doors, doors sticking, and visible sinking on one side of the building.
The mortar between bricks is cracking, crumbling, or falling out, leaving gaps in the brickwork.