Plaster blown,
cracked or
coming away?
Hollow plaster has already let go of the wall behind it. Filling and painting over it puts the problem back for a year. Here is how to tell what you are dealing with.
Tap it. That tells
you almost everything.
Run your knuckles across the wall. Sound plaster is dull and solid. Where it sounds hollow or drummy, the plaster has debonded from the wall behind and is being held up by the paint and its own edges. That area will not take a skim, a filler or a wallpaper. It has to come off back to something solid.
Fine hairline cracking that follows no particular direction is usually shrinkage in the plaster or the decoration and is cosmetic. A straight crack that follows a line, especially at a ceiling to wall junction or diagonally from the corner of a door, is telling you about movement behind the plaster rather than in it.
Plaster that is blown low down on a ground floor wall, often with a tide mark and sometimes with salt crystals on the surface, is a damp symptom and not a plastering problem. Replastering it without dealing with where the water is coming from produces exactly the same wall again within two years, which is the single most common wasted spend in this trade.
Three different jobs
people use one word for.
Skimming is a thin finishing coat over a surface that is already sound and flat. It is what you want when the walls are structurally fine but the surface is tired, patched or textured. It is quick, it is comparatively cheap, and it will not rescue a wall that is blown underneath.
Replastering means taking the failed material off and building the wall back up in coats: a backing coat to get flatness and a finish coat on top. It is the right answer where plaster has debonded, or where the original is so uneven that a skim would not hide it.
Overboarding means fixing plasterboard over the existing surface and skimming that. On ceilings it is often the sensible answer because it avoids bringing down a heavy, dusty ceiling, and it is fast. It costs a small amount of room height and it means anything behind it stays behind it.
Which one is right is usually decided by tapping the wall and by what your survey says, not by preference.
Old ceilings deserve
a decision, not a guess.
In Victorian and Edwardian London, ceilings were built from timber laths with plaster pushed through the gaps to form nibs on the other side. Those nibs are what hold the ceiling up. Over a century they get brittle and break, and the ceiling starts to sag away from the joists.
The safety point is real. A lath and plaster ceiling that has lost its nibs over a large area can come down in one piece and it is heavy. Signs to take seriously are visible sagging, long cracks running parallel to the joists, and a bulge that moves if you press it gently.
There are two honest options. Overboarding fixes plasterboard through the old ceiling into the joists above, which supports it and gives a new surface. Full replacement takes the old ceiling down entirely, which is dirtier and more disruptive but removes the question permanently, and it is the only option where the laths themselves have gone.
Original cornice and ceiling roses complicate this and are usually worth saving. They can be protected and worked around rather than lost, but that has to be planned rather than discovered on the day.
Somebody has to
tidy up afterwards.
Most plastering work in a survey led project is not decorative, it is making good. A rewire means chased walls. A damp proof course means the plaster comes off to a metre and goes back in a salt resisting mix. Removing a chimney breast leaves three walls needing attention.
This is where jobs commonly fall apart, because the electrician does not plaster and the plasterer did not do the chasing, and the homeowner ends up holding the gap between two trades who each say it is the other one.
One firm doing both is not a sales line, it is the specific problem being solved. We plaster after our own first fix work, so there is nobody to blame and no second mobilisation to pay for.
Questions we get
asked most.
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price.
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What plasterers do when a wall is taken back.
Replastering is a sequence, and skipping any part of it is why a wall comes back. The old plaster is taken off back to the brick, the joints are raked where they are loose, and the wall is left to show what it is actually made of. Only then can plasterers decide between a sand and cement render coat with a gypsum finish, a lime system on a solid wall, or boarding out where the background is too uneven to float economically.
Where a wall has been damp, the salts that came up with the moisture are still in it, and they will pass through new gypsum and show as staining within months. That wall needs either a salt retardant additive in the render coat or a lime system that can handle it, plus time to dry before anything is applied. Plasterers who skim a damp wall on the Friday it was hacked off are giving you a finish that lasts until the first cold snap.
Areas we cover.
We take replastering work across all 32 London boroughs. Most of our work is in west London, in Shepherd's Bush, Hammersmith, Fulham, Kensington, Chiswick and White City, and in south west London, in Putney, Wandsworth and Wimbledon. We also work in south east London, in Greenwich, Blackheath and Lewisham.
If your property is outside these areas, call us anyway. We travel across London and will tell you honestly if a job is too far to price properly.