Signs Your Walls Need Replastering

Not sure if your walls need replastering or just redecorating? Here are the warning signs that indicate it's time to call a professional.

Published 17 August 2026 by Exeter Plastering Co

Plaster doesn't last forever. After years of settling, moisture, and general wear, it can deteriorate to the point where filling and painting won't fix the problem. Here's how to tell when replastering is needed.

1. Hollow Sounds When You Tap the Wall

Tap your wall gently with your knuckles. A solid, dull thud is normal. A hollow, drumming sound means the plaster has come away from the wall behind it. This is called "blown" plaster.

Blown plaster happens when:

• The bond between plaster and wall fails (often due to moisture)
• The building has settled and movement has cracked the adhesion
• The original plaster was applied to a dusty or unsuitable surface

Blown plaster will eventually fall off, so it needs replacing. You can't fix it with filler.

2. Cracks That Keep Coming Back

Small hairline cracks are normal and can be filled. But if you fill a crack and it reappears within months, that's a sign of a deeper problem.

Recurring cracks suggest:

• Ongoing movement in the building
• The plaster is too old and brittle
• There's a structural issue that needs addressing first

If cracks keep reappearing, replastering won't fix the problem permanently unless the underlying cause is addressed. Get a surveyor's opinion if cracks are severe or widening.

3. Bulges or Bumps on the Surface

If you can see or feel bulges, ripples, or lumpy areas on your walls, the plaster is failing. Bulges form when:

• Moisture gets behind the plaster and causes it to expand
• The plaster has lost adhesion and is sagging
• Salts from the wall are pushing the plaster outward

Bulging plaster should be removed and replaced. It will continue to get worse if left.

4. Damp Patches or Staining

Brown, yellow, or dark staining on walls is usually a sign of moisture. If the staining won't paint over and keeps reappearing, you likely have damp getting into or through the wall.

Common causes:

• Leaking pipes inside the wall
• Rising damp from the ground (common in older properties without a damp-proof course)
• Penetrating damp from outside (failed pointing, blocked gutters, render damage)
• Condensation in poorly ventilated rooms

Fix the source of moisture first, then replaster. Plastering over damp walls just traps the problem and causes the new plaster to fail.

5. Powdery or Crumbling Surface

If your plaster feels dusty, powdery, or crumbles when you touch it, the plaster has broken down. This is particularly common in older properties or rooms that have experienced damp.

Causes include:

• Old age (plaster can last 50-100 years, but not forever)
• Moisture damage weakening the plaster over time
• Salts from the wall crystallising and breaking down the plaster

Powdery plaster can't be saved. It needs removing and replacing.

6. Peeling or Flaking Paint That Won't Stick

If paint peels off in large sheets no matter how well you prepare the surface, the plaster underneath is likely failing. Paint adheres to sound plaster. If it won't stick, there's a problem with the substrate.

This often indicates:

• The plaster surface has broken down
• Moisture is present beneath the paint
• The wrong type of paint was previously used (non-breathable paint on lime plaster, for example)

7. You've Just Had Damp Treatment

After damp-proof course injection or tanking, the old plaster has to come off. Damp treatment chemicals make the plaster unsuitable for reuse, and new plaster is needed to complete the job.

Use breathable plaster (or sand/cement render) in areas where damp proofing has been applied. Standard gypsum plaster isn't suitable.

8. Large Areas of Damage

Minor damage can be patched. But if more than about 30% of a wall is damaged, it's often more cost-effective and better-looking to replaster the whole wall.

Patching large areas can result in:

• Visible differences in texture or colour
• Uneven surfaces that show up under raking light
• More work than just re-skimming the whole wall

When a Re-skim Is Enough

Not all damaged plaster needs full replastering. A re-skim (applying a thin finishing coat over sound plaster) works when:

• The existing plaster is solid and well-bonded
• You're removing wallpaper and the surface beneath is rough
• There are only minor surface imperfections
• You want a smooth modern finish over old textured plaster

A re-skim costs less than full replastering and is much quicker. A good plasterer can tell you during a site visit whether a skim will suffice or full replastering is needed.