A quality wall plaster needs three things: a smooth, even finish; strong adhesion to the wall surface; and resistance to cracking as the building settles and temperature changes. The sand you use determines all three. Coarse or badly graded sand produces a rough finish that requires multiple coats and still shows defects. Sand with high silt or clay content shrinks as it dries, causing the characteristic hairline cracks you see on plastered walls within months of construction.
M Sand is engineered for concrete — it has angular, coarse particles (up to 4.75mm) and some silt content (up to 8% per IS 383). These properties are fine for structural concrete but terrible for plaster. The angular particles do not pack smoothly; the coarser sizes leave a gritty texture; and the permitted silt content, while acceptable for concrete, is enough to cause cracking in a plaster coat.
P Sand (Plastering Sand) is manufactured to much tighter specifications than M Sand. Particle size: 150 microns to 2.36mm (much finer than M Sand). Silt content: 0% — completely removed. Powder and dust: 0% — washed and screened. The result is a sand that packs tightly, bonds strongly to cement and wall surfaces, dries evenly, and produces a smooth, crack-resistant finish ready for paint or tile work.
Replastering a wall is expensive — typically 3–5x the cost of the original plaster work, plus the disruption. If you are building a new home, using the right P Sand from the start costs marginally more than M Sand but saves significantly on cracked plaster repairs within 1–2 years. Always specify P Sand to your contractor for all interior and exterior wall plastering work.
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