Replaster or Just Fill? How to Tell With Your Walls

The tap test: hollow means trouble

The most useful check is to knock gently across the wall with your knuckles. Sound plaster that is well stuck gives a solid, dull thud. A patch that sounds hollow, drummy or papery has 'blown'. That means it has come away from the wall behind it. Filler will not fix a blown area, because there is nothing solid holding it in place.

Blown plaster is common in older Stirling homes, especially stone terraces and Victorian tenements. It shows up on outside walls where damp has crept in over the years. Mark the hollow areas with a pencil. If they cover more than the odd patch, you are looking at replastering, not filling.

What filler can genuinely handle

Plenty of tired walls look worse than they are. If the plaster underneath is solid and only the surface is damaged, filler and a bit of patience will do the job. These are jobs a competent homeowner can often tackle over a weekend.

• Fine hairline cracks, especially above doors and windows where the house has settled
• Small chips and dents from furniture, radiators or pictures being removed
• Screw and rawlplug holes
• Shallow surface scuffs where the paint has pulled away but the plaster is firm

Signs you are past filling

Some problems point to replastering, or a fresh skim over the whole wall. Watch for cracks wider than a couple of millimetres, or ones that keep coming back after filling. These usually mean movement, or plaster coming away underneath. A wall that bulges, feels soft or crumbles to dust when you scrape it has failed and needs taking off.

Watch for damp too. Brown tide marks, salty white marks or bubbling paint all mean water is getting in. In Central Scotland that is often rain driving onto a gable wall or an old chimney breast. Filling over damp plaster just traps the problem, and it comes back within months. The cause of the damp has to be fixed first, then the damaged plaster replaced.

Skim, patch or full replaster

Even when replastering is needed, it is rarely all or nothing. Most of the wall may be sound but uneven, or covered in old artex and patches. Then a skim coat is enough. A skim of roughly 2 to 3mm over the whole wall gives a fresh, flat finish. If only one part has blown, patching it and reskimming that wall keeps the cost down.

A small patch is a quick job. Skimming a full room is a bigger one, and the price depends on size, ceiling height and access. Bare-back replastering, where old plaster comes off and fresh coats go on, is a bigger job again. We look for free and give you one fixed price before any work starts. Any honest plasterer will happily tell you when a job is genuinely a filler and roller weekend rather than a paid one.

Common questions

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