A new wall can look fine for a week and then show hairline cracks, sandy patches or a surface that won't take putty evenly. Often the problem started with the sand. Wrong grade, too much mud, or sand that wasn't sieved at site — and the plaster shows it.
What makes good plastering sand
Plastering sand should be fine, clean and low in mud or silt. Fine grains let the mason spread a thin, even coat. Clean sand means cement can bind properly instead of fighting clay and organic muck. If you rub a wet pinch between your fingers and it leaves a muddy stain, that load is dirty — send it back or sieve hard before you use it.
Why Ganga sand is the usual choice in Patna
Around Patna, Ganga balu is the sand most masons ask for when the job is plaster. It's fine and light in colour, mixes into a smooth mortar, and leaves a wall that takes paint well. That's why you'll hear people call it white sand or safed balu even though it's really a pale grey. For finishing coats, it beats coarser options almost every time.
Inside plaster vs outside plaster: what changes
Inside walls usually get thinner coats and a smoother finish, so fine Ganga sand is ideal. Outside plaster faces rain and sun; some masons prefer a slightly richer mix or a touch of coarser sand in the first coat for grip, then fine Ganga sand for the final coat. Follow your mason or engineer — local practice varies by house type and exposure.
Can you use M-sand or P-sand for plaster?
Manufactured sand (M-sand) and plaster sand (P-sand) are common in other parts of India. In Bihar, river sand is still what most sites use for plaster because it's available and masons know how it behaves. If someone offers M-sand for plaster, ask whether it's graded for finishing and check a sample on a small patch first. Don't switch mid-job without talking to your mason.
Three mistakes to avoid
- Dirty sand. Mud and silt weaken plaster and cause patches. Do a quick glass-of-water test when the load arrives.
- Not sieving at site. Even decent sand can have lumps. A quick sieve before mixing saves rework.
- Poor curing. Good sand won't save plaster that dries out too fast. Keep walls damp as your mason advises, especially in hot weather.
How much sand for plastering a room
Rough guides exist (often a few CFT per 100 sq ft of wall, depending on thickness), but wall height, double coats and openings change the number a lot. Tell us the size of the rooms and whether it's a first coat or re-plaster, and we'll help estimate a tractor load. Always confirm the final quantity with your mason before you book.
For the difference between Ganga and Sone sand, see Ganga Sand vs Sone Sand.