Wall plastering in Singapore: the full guide
What plastering actually does
Plaster is the layer between your wall and your paint. On most Singapore jobs it is either a thin skim coat over an existing surface, or a cement render where the substrate is rough or has been hacked back. Paint does not hide a bad wall. It follows every ripple, and gloss follows them worse than matt.
When a wall needs it
Run your hand across the wall in raked light from a window. If you feel ridges where old paint was patched, if a knuckle tap sounds hollow in places, or if you can see trowel lines through two coats of emulsion, the wall needs skimming before it sees any more paint.
Hollow spots matter more than cracks. A hollow area means the plaster has debonded from the substrate. Paint over it and eighteen months later the whole patch comes away in a sheet, and your topcoat leaves with it.
The materials we use and why
Cement render goes on structural walls, wet areas and anywhere that sees moisture. It is harder, slower to cure, and it tolerates the humidity in a Singapore kitchen or bathroom.
Gypsum skim goes on interior walls that are already sound. It sands to a finer finish than cement and takes paint beautifully, but it softens if it gets wet, so it stays out of shower walls and service yards.
Lime plaster comes up on older shophouse and conservation work, where a cement render would trap moisture behind it and blow the wall.
Why humidity changes the job here
Plaster cures by losing water. At 80 percent ambient humidity it loses that water slowly, so a coat that would be paintable in three days in a dry climate can still be green on day five here. Painting a green wall seals the moisture in. It shows up as blistering, patchy sheen, or a bloom of salts on the surface within a few months.
We check with a moisture meter rather than by eye. Under 12 percent and the wall takes paint. Above that, it waits, and we tell you the job has moved a day.
The process, start to finish
Furniture comes out or gets sheeted, then loose material is hacked back to sound substrate. Anything smooth or previously painted gets a bonding agent first, because plaster will not grip gloss. The render or skim goes on in two passes rather than one thick one, since a thick coat cracks as it shrinks. Then it cures, gets sanded, and takes a sealer before any paint.
The sanding stage is where most of the finish quality lives, and it is the stage a cheap quote leaves out.
Where DIY plastering goes wrong
The four failures we get called to fix, in order of how often we see them: mixing too wet so the plaster slumps and cracks, skipping the bonding agent on a painted wall, laying one thick coat instead of two thin ones, and painting before the wall has cured.
All four look fine on the day. All four show up between six and twenty-four months later, and fixing them costs more than the original job because the failed layer has to come off first.
What it costs
Skim coat is quoted per square foot, from $3.50. Cement render starts at $6.50 per square foot because it is slower and heavier. Crack filling and small patch repairs are folded into a painting quote rather than billed separately.
Hacking off failed plaster, treating mould and repairing water damage are itemised. You can see what each one costs and drop any of them.
Questions worth asking any plasterer
Ask what they are skimming with and why that material suits the room. Ask how long they will leave it to cure before painting, and what they will use to check. Ask whether the price includes sanding and priming, because a quote that stops at the render is not a finished wall.
If the answer to the curing question is a number of days with no mention of measuring, get a second quote.
