What is plaster skimming? A plain-English guide
What a skim coat is, when walls need skimming, and why plasterers price it at around 18 m² per day.
Updated 2 September 2026
Skimming is the thin finishing coat of plaster that gives a wall or ceiling its smooth, paintable surface. It is applied as two wet layers of multi-finish over plasterboard or old plaster, at roughly 18 m² per day for the £230 Swindon day rate. One 25 kg bag covers about 10 m². People say "plastering" and "skimming" as if they were the same job — an easy mix-up, and a costly one, because the two can be quoted as entirely different pieces of work. Knowing which one you need is the difference between one visit and a replaster. And a skim coat fixes surface finish, not structure — it will not straighten a badly uneven wall or cure damp; those need boarding or a damp specialist first.
What a skim coat actually is
A skim coat is a layer of finishing plaster only a few millimetres thick. It is not structural; it smooths and evens an existing surface. On new plasterboard it is the final surface; on old walls it hides minor imperfections and old paint texture. Because it is so thin, it follows the wall rather than straightening it, which is why badly uneven walls need boarding or replastering first, not a thicker skim. The finished result should be flat, smooth and ready for paint without sanding.
When a wall needs skimming
Walls are skimmed after plasterboarding, after a rewire has left chases to fill, or when old plaster is sound but the surface is tired. If the old plaster has blown or crumbled, it should be removed and the wall replastered rather than skimmed over, or the finish will fail. A local plasterer can tell the difference by tapping the wall and checking for hollow, drummy patches, and will only skim a surface that is sound enough to take it.
How it is priced
A plasterer skims about 18 m² per day. A 3 m × 4 m room with a 2.4 m ceiling is roughly 45 m², so it takes three days and about £690 in labour before materials. Bonding bare brick first adds a day and pushes the coverage down to 2.7 m² per bag of bonding coat. The full method is explained in how much plastering costs. Because skimming is priced by area, the room size and ceiling height matter more than anything else.
Skimming vs plastering
People often use the two words as if they were the same, but skimming is one specific job. Plastering is the whole trade, which also includes bonding, rendering, lime work and boarding. When you ask for a "replaster", make clear whether you mean a fresh skim over the existing surface or stripping back to bare brick and starting again, because the price and the number of visits are very different. Being specific about the method also stops two different plasterers from quoting for two different jobs.
Common skim problems
The finish can crack if the wall behind it moves or if the plaster dried too fast. Small shrinkage cracks are normal and easily filled; wide or spreading cracks point to a problem underneath. A patchy or powdery surface usually means the plaster was over-worked or dried too quickly. If you spot a problem in the first days, raise it with the plasterer while it is fresh, because most good tradespeople will come back and put a small issue right.
Aftercare and painting
Let a skim coat dry for one to two weeks before painting, then start with a watered-down mist coat. Sanding is not needed on a good skim; if the surface feels gritty, the plasterer can polish it while it is still workable. See the plastering process guide for what happens on each visit and how long to wait. Keeping the room ventilated while it dries helps the plaster cure evenly and avoids the dark patches that delay decorating. And that is the plain-English promise kept: a skim coat is a specific job — now you know when your wall needs one, what it costs and what to ask for, rather than paying for "plastering" and hoping.
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What is plaster skimming? A plain-English guide: quick questions
How thick is a skim coat?
A skim coat is typically 2 to 3 mm thick, thin enough that it smooths the wall without changing its dimensions. If a wall needs significant levelling, that is a separate job, usually boarding or bonding first.
Can you skim over wallpaper?
No. Wallpaper must come off first; plaster will not bond to it, and any paste left behind can cause the new skim to fail. Stripping paper is preparation you can do yourself to keep costs down.
How much does a skim coat cost?
Labour runs at £230 per day at roughly 18 m² per day, so a 45 m² room is about £690 before materials. Materials add a few pounds per square metre. For room-by-room figures see plastering costs in Swindon.
Do I need to skim before wallpapering?
You can paper over sound old plaster if the surface is flat and clean, but skimming first gives a smoother base and hides old texture and minor marks. If the wall is uneven or has been painted with gloss, skimming is the better preparation and makes the paper hang cleanly.