Signs by floor type
| Floor | What you might notice |
|---|---|
| Tiles or stone on screed | Dark or damp grout lines, a warm tile, white salts in the grout, tiles that sound hollow or crack, water at the edge of the floor. |
| Laminate, LVT or engineered wood | Boards that lift, cup or separate at the joints, a soft or springy spot, water coming up at the edges or thresholds. |
| Carpet | A damp or cold patch, a musty smell, gripper rods and underlay stained at the edge, mould at the skirting. |
| Timber floorboards upstairs | A stain or bulge in the ceiling below, drips at a light fitting, boards that feel damp or smell. |
| Suspended floor downstairs | Damp air, a musty smell, condensation, the heating losing pressure or the meter moving with little else to see. |
| Underfloor heating | The boiler losing pressure, a patch that stays warm with the heating off, salts or damp in the manifold cupboard, a zone that will not heat. |
Signs on any floor
- The water meter moves when every tap and appliance is off. This points to the water supply.
- The boiler keeps losing pressure with no drips anywhere. This points to the heating.
- A higher water bill than the same period last year, with no change in use.
- A hiss or trickle when the house is silent, often clearest at night.
- Damp at the base of walls that is new, or that appeared after the floor changed.
- A floor that is warmer in one area than it used to be.
Several of these together make a hidden leak much more likely than one on its own.
Things that look like a leak under the floor
Plenty of damp floors have no leak under them. The common causes:
- A leak somewhere else that runs along the floor: a shower tray seal, a bath waste, a toilet connection, a dishwasher or washing machine hose. In one review, what looked like an underfloor heating leak was a toilet pipe, with the water travelling under the floor.
- Condensation, especially on cold solid floors under rugs or in bathrooms, which comes and goes with the weather.
- Rising or penetrating damp from outside, which usually follows external walls and does not move a meter or a pressure gauge.
- Spills and cleaning that have soaked into a floor finish.
A proper survey tests the pipes rather than guessing from where the damp is. If the pipes all hold pressure, you know to look elsewhere, which is useful to know before anything is dug up.
What to do next
Do the simple meter and boiler checks to see which system is involved, turn the water off if it is coming up through the floor, and take photos. Checks you can do safely. Then call and describe what you have found.
Guides by floor: underfloor heating, concrete and screed, floorboards.
