How-to
P-Sand for Plastering: How to Get a Smooth, Crack-Free Wall
A good plaster job is mostly about three things: the right sand, the right ratio, and proper curing. Here is how to get all three.
Plaster is the finish people actually see and touch, so its quality matters as much as the structure behind it. The most common plaster problems — cracks, a rough surface, hollow patches — usually trace back to sand choice, mix ratio or curing. Here is how to get each right.
Start with the right sand
Use P-Sand (plastering sand), not coarse concrete sand. Its finer, uniform grains spread smoothly, reduce rebound (material falling off as you work), and leave a clean surface that needs less putty afterwards. The sand should be clean and low in silt — silty sand is a leading cause of plaster cracks.
Get the ratio right
Typical cement-to-sand ratios for plaster:
| Coat / location | Common ratio (cement : sand) |
|---|---|
| External / rough wall | 1 : 4 to 1 : 5 |
| Internal walls | 1 : 5 to 1 : 6 |
| Ceiling | 1 : 3 to 1 : 4 |
Richer (more cement) is not always better — too much cement increases shrinkage and can cause cracks. Match the ratio to the surface.
Work in the right thickness
- Keep each coat to a sensible thickness — roughly 12–15 mm for walls; build up in two coats if you need more rather than one thick layer.
- Dampen the wall before plastering so it does not pull water out of the mix too fast.
Cure properly
Keep the plastered surface damp — by sprinkling water — for at least 5 to 7 days. This lets the cement gain strength slowly and evenly, which is what prevents fine surface cracks.
Common mistakes to avoid
- Using coarse or silty sand instead of clean P-Sand;
- Over-cementing the mix in the belief it makes plaster "stronger";
- Plastering onto a dry, dusty wall;
- Skipping curing because the surface "looks dry."
Get the sand and the curing right, and most plaster problems simply never appear.
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Wilgro Infra supplies washed M-Sand, P-Sand and graded aggregates across Sarjapur, Hosur, Attibele and all over Bangalore — by the tonne or by the load, with sieve reports on request.