Homeowner guide
Skimming vs Replastering: Which Does Your Wall Need?
Ask two people what your cracked wall needs and one will say skim it, the other will say hack it off. Both can be right. The choice depends on what is going on underneath the surface, not on how the wall looks from across the room.
What skimming actually is
A skim is a thin finishing coat of plaster, usually a few millimetres, applied over a surface that is already sound. It gives a smooth, fresh face ready for decoration. It hides surface faults such as fine cracks, old filler, uneven paint build up and the marks left by removing wallpaper.
What a skim cannot do is fix a wall whose backing has failed. If the plaster underneath is loose, the new skim bonds to something that is itself coming away.
What replastering involves
Replastering means removing the old plaster back to the brick or block, then building the wall up again, either with a backing coat and finish or by fixing plasterboard and skimming it. It is messier, takes longer and needs more drying time, but it deals with the cause rather than covering it.
How to tell which your wall needs
The tap test tells us most of what we need to know. Solid walls sound dull. Areas that sound hollow or drummy have lost their key to the masonry.
- Skim is usually enough: fine cracks, sound plaster, old wallpaper damage, rough previous repairs
- Replaster is usually needed: large hollow areas, crumbling or powdery plaster, plaster blown by damp
- Plasterboard walls: damaged boards are replaced and skimmed rather than replastered
- Ceilings: a sound ceiling can be skimmed; a sagging or cracked old ceiling is often better overboarded
Damp changes the answer
Plaster that has been soaked by a leak or rising moisture often turns soft, salty or powdery. Skimming over it traps the problem and the new finish blisters or stains. In that case the cause of the moisture has to be fixed first, the old plaster removed and the wall allowed to dry before new plaster goes on. Our guide to damp and condensation in rented property explains how to tell condensation apart from other moisture sources.
Drying time and decorating
A fresh skim needs to dry thoroughly before painting, and a full replaster needs longer still. Painting too early traps moisture and leads to peeling. New plaster should be sealed with a suitable mist coat rather than standard emulsion. We will give you honest timings on the quote so decorating can be planned properly, and because decorating is one of our trades, we can take the job through to the final coat.
Getting it assessed
A free quote visit is the quickest way to settle it. We tap test the walls, look for moisture and tell you which approach will last. Where only part of a wall is hollow, we will often replaster that section and skim the rest so the whole wall finishes as one surface. All plastering work carries our 1-year workmanship warranty.
Frequently asked questions
Can you skim over painted walls?
Yes, if the paint and plaster underneath are sound. The surface is prepared with a bonding treatment first.
Can you skim over cracks?
Fine surface cracks, yes, often with scrim tape. Cracks from movement or hollow plaster need investigating first.
Is replastering much messier than skimming?
Yes. Removing old plaster creates a lot of dust and debris, so rooms are sheeted and cleared before we start.
When can I paint new plaster?
Only once it is fully dry and has changed to an even pale colour. We will tell you when it is ready.
Do you plaster ceilings too?
Yes. Ceiling repairs, skimming and overboarding are all part of our plastering work.
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