Costs & advice
Skimming or replastering — which do I need?
The difference is significant in both cost and mess, and there is a quick test that tells you most of what you need to know.
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What the two words actually mean
Skimming is a thin finishing coat — usually two or three millimetres — applied over a surface that is already sound and reasonably flat. It gives you a smooth finish ready for decorating. It is quick, comparatively cheap and comparatively clean.
Replastering means taking the failed material off and building the wall back up: repairing or preparing the background, applying backing coats, fitting beads where needed, and then finishing. It costs more and makes considerably more mess, because there is genuinely more work in it.
The words get used loosely, including by people quoting you, so it is always worth checking which one a price actually covers.
The ten-second test
Go and tap your wall with a knuckle. Work across it — high, low, near the window, behind where the radiator is, in the corners.
- Solid, dull, no give. The plaster is bonded to what is behind it. This is a candidate for skimming.
- Hollow, drummy, a bit like a drum skin. The plaster has come away from the background. That area is "blown" and it has to come off — skimming over it adds weight to something already failing.
A patch or two of hollow in an otherwise sound wall is a repair job followed by a skim. Hollow across a large proportion of the wall points to a replaster.
Other things that push it towards a replaster
- Anything damp
- Active moisture has to be resolved first, whatever else happens. Plastering over a wet wall fails, and salt staining comes back through the new finish.
- Cracks that keep coming back
- A crack that reopens after being filled is reporting movement rather than causing it. That needs diagnosing before any plastering, or you will pay for the same wall twice.
- Loose, powdery or crumbling surface
- If it comes off on your hand or a screwdriver goes in easily, there is nothing there for a new finish to grip.
- Old, unsuitable coatings
- Some historic paints, textured coatings and sealers stop new plaster adhering. They either come off or get sealed appropriately, and that is preparation work either way.
- Modern plaster on a solid, breathable wall
- A common pattern in older Shropshire properties: gypsum or cement over a wall built to breathe, now blown at low level with salts showing. That is not a finish problem, it is a specification problem, and skimming over it repeats the mistake. See our lime plastering page.
- Very uneven walls
- A skim follows the shape it goes on. Genuinely straightening a wall means building it out or dry lining it — see dry lining.
What each involves in practice
| Skim | Replaster | |
|---|---|---|
| Existing plaster | Stays | Comes off, in whole or in part |
| Mess | Moderate | Considerable — dust and waste |
| Waste | Minimal | Significant, and it has to be disposed of |
| Time on site | Shorter | Longer, with coats between |
| Drying time before decorating | Shorter — thin coat | Longer — much more water in the wall |
| Cost | Lower | Higher |
| Fixes underlying problems | No | Yes, if the cause is dealt with too |
The middle ground
Most real jobs are not one or the other. A typical room might need two blown patches cut out and made good, a crack raked and reinforced, and then the whole wall skimmed. That is normal and it is the reason a quote based on square metres alone rarely survives contact with the actual wall.
What to send for a quote
- A wide photo of each wall you want covered
- Close-ups of any cracking, blown areas or previous repairs
- A note of where the wall sounded hollow when you tapped it
- Anything you know about damp, leaks or movement, even historic
- The approximate age of the property
That last one matters more than people expect. A pre-1919 solid-walled property and a 1990s plasterboard house need different answers to the same-looking problem.
Common questions
Can I tell which I need myself?
You can get most of the way there with the knuckle test described above, plus a look at whether anything is damp, cracked or moving. What you cannot judge from the surface is suction, contamination and whether a previous coating will hold — those need someone who has done it before.
The plasterer says it needs a full replaster and I was quoted for a skim elsewhere. Who is right?
Not necessarily either — they may be quoting for different work. Ask the one recommending a replaster to show you which areas sound hollow and why. A good plasterer will happily tap the wall in front of you. If the answer is vague, get a third opinion.
Is replastering always better?
No. If the existing plaster is sound, taking it off and starting again is money and mess for no benefit. Skimming a good background is the right answer far more often than not, and a plasterer recommending it is usually being straight with you rather than cutting corners.
What about walls that have been dot-and-dabbed?
Plasterboard fixed with adhesive can usually take a skim well, provided the boards are secure and the joints are sound. Press firmly in the middle of a board — noticeable flex means the fixing is not right, and skimming over a moving board will crack.