Sign of damp
Crumbling plaster
Plaster that turns to sand when you press it, falls away in chunks, or sounds hollow when tapped. Often found low on walls, around windows, under bathrooms and on external walls, usually with salts, staining or peeling paint around it.
What it might mean in a flat
Soft, powdery or hollow plaster.
Plaster that crumbles has usually been wet for a long time, often through several monsoons. Patch repairs with fresh plaster and paint can hide it for a season, but if the water source stays, the new plaster goes the same way. Hollow-sounding plaster may also have lost its bond and could come away.
Common causes
- Long-term moisture weakening the cement plaster and its bond to the brick or block behind
- Salts crystallising inside the plaster and breaking it up from within
- Rain driving through cracks in the external plaster on monsoon-facing walls
- Rising damp at ground-floor skirting
- A leaking concealed pipe keeping one section wet
What an inspection checks
How we confirm it.
- Tapping to find hollow areas, marked on the floor sketch
- Pin and pinless meter readings across the area and around it, against the dry reference, keeping in mind that salts in crumbling plaster can raise pin readings
- Thermal scan of the whole wall, with each cool area confirmed by the meter
- Tracing the water path from the location: external face, window, bathroom, pipe route or ground
When to worry
Signals that it's active.
- Large hollow areas, especially on a ceiling
- Readings stay high, so the wall is still wet
- Fresh patch repairs in a resale flat, which can mean the problem was covered recently
Where it usually comes from
Questions buyers ask
Can crumbling plaster just be re-plastered?
Yes, once the water source is fixed and the wall has dried. Re-plastering a wet wall usually breaks down again within a season or two.
Do you remove plaster to check?
No. Megahedge does not drill, cut or open walls. Hollow areas are found by tapping and recorded.
Is hollow plaster on the ceiling a concern?
It can come away, so it should be looked at by whoever repairs it. The report marks it clearly.
Not ready to book? Walk the flat with our 10-minute self-check and get a snag list to take to the seller.
Start the Damp CheckFind the damp before you pay for it.
Book a moisture and thermal inspection. Report on WhatsApp within 24 hours.