Putty Quantity Calculator
Area × coats × consumption to bags.
Inputs
Result
Formula
| Per coat = base consumption × substrate factor | |
| Total = per coat × coats × area | |
| Bags = ceil(total ÷ bag size) |
200 m² of cement plaster with two coats of water-resistant putty: 1.35 kg/m² per coat, 2.70 per m², 540 kg total, 27 bags of 20 kg. On a rough wall (1.3 factor) it becomes 702 kg and 36 bags.
FAQ
Why is water-resistant putty both dearer and heavier to use?
It contains more redispersible polymer and water repellent, is denser and covers better, so more material goes on per square metre. It also resists damp, does not powder or shell off - essential in humid regions and around kitchens and bathrooms. The saving on material is nothing against one redo.
How many coats, and can one thick coat do?
Two: the first levels, the second tightens. A single thick coat dries unevenly - skin first, core later - and cracks while it shrinks, and sands through easily. Codes limit each coat to about 1 mm of water-resistant putty and total thickness to 2-3 mm; beyond 5 mm it may detach, so level with gypsum plaster or mortar first.
Putty versus gypsum levelling?
Gypsum levelling plaster handles large thicknesses - 5-20 mm in one go - with high strength and fast drying, but poor water resistance, so dry interiors only. Putty is a 2-3 mm finish coat. The order is substrate preparation, gypsum levelling, putty, primer, topcoat. Using putty to fill a 10 mm hollow will always crack.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.