Damp plaster is a symptom, not a cause. Before any replastering is done, the source of damp must be identified and resolved — otherwise the new plaster will fail just as the old did.
Signs of Damp Plaster
- Dark patches or tide marks on walls
- Peeling paint or wallpaper
- White salt deposits (efflorescence) on the surface
- Soft or crumbling plaster that sounds hollow
- Musty smell in the room
Common Causes of Damp Plaster
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| Cause | Location | Solution |
|---|---|---|
| Rising damp | Ground floor walls, near floor level | DPC injection + replaster with salt-resistant render |
| Penetrating damp | Exposed walls, around window frames | Fix external defect, dry out, replaster |
| Condensation | Cold external walls, bathrooms | Improve ventilation, insulation |
| Plumbing leak | Around pipes, ceilings below bathrooms | Fix leak, allow to dry, replaster |
| Roof leak | Ceilings, top floor walls | Fix roof first, then replaster |
Should You Replaster Over Damp Walls?
Never. Plastering over damp walls is a waste of money — the moisture will push through the new plaster and cause it to fail. Always fix the source first, allow the wall to dry thoroughly (which can take weeks in bad cases), and then replaster.
Cost to Replaster After Damp Repair
Replastering a damp-affected area after the damp has been treated typically costs £200–£600 for a small area to £800–£2,000 for a whole wall or room. Saltproof render is used in rising damp situations, which adds a small material premium.
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