Skim or replaster: which does your wall actually need?

What a skim coat is

A skim is a thin finishing coat applied over a surface that is already sound. It gives a smooth, even face ready for decorating. It works well over old walls that are solid but uneven, over ceilings with a tired or textured finish, and over new plasterboard.

The key word is sound. A skim does not strengthen anything. If the plaster underneath is loose, hollow or crumbling, a fresh skim on top will crack or blow along with it.

When patch repairs are enough

Many walls are mostly fine with a few bad areas: where a fitting has been ripped out, where old pipes have been chased in, or where a knock has broken the surface. Those areas are cut back to firm material, built up and finished flush with the surrounding wall.

Patch repairs are common in bathroom work. Once old tiles come off, the plaster behind is often damaged in places, and it is repaired before the next stage begins rather than hidden.

When a wall has to come back

Some signs mean a skim would only be a cosmetic cover. We check for these by tapping the wall and looking closely before recommending anything.

• A hollow sound over large areas when the wall is tapped
• Plaster that crumbles or powders when touched
• Bulging areas that move under hand pressure
• Salting or staining that points to a damp problem

Plaster and damp are separate questions

Plaster that has failed because of damp should not simply be replaced. The cause comes first. Damp proofing is a separate service that Martin surveys and quotes as its own job, and any plastering after treatment is planned once the cause has been dealt with.

Where the problem is condensation rather than damp in the wall, better ventilation usually does more good than new plaster. Our damp and mould guide explains how to tell the difference.

Drying and decorating

Fresh plaster needs time to dry before it is painted, and painting too early traps moisture and causes flaking. We explain drying expectations at the end of every plastering job so decorating can be planned properly.

How we approach a plastering visit

When Martin looks at a wall, he starts by asking what happened to it. A wall damaged by an old fitting, a wall that has been painted many times over and a wall that has been wet for years all look tired, but they need completely different answers. Tapping across the surface finds hollow areas, running a hand over it finds loose material, and looking at the edges of any cracks shows whether they are old and stable or still moving.

From there the recommendation is usually clear: a skim over a sound surface, local repairs where the damage is contained, or taking the wall back where the plaster has lost its grip. You get that reasoning explained, not just a price, so you can see why the job is being done the way it is.