Plaster calculator

Bags of finish plaster for a skim, or backing and finish for float and set, from the area of the walls and ceilings.

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Measure the rooms once, walls, openings and ceilings, and SiteHelm PRO works out the plaster, beads and scrim, then puts them into an order or a quote. Save it to the job.

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Worked example

Skimming 30 m² of new plasterboard walls and ceiling:

4 bags of finish plaster (25 kg)

30.0 m², with 10% extra
About 38 m of scrim tape for the board joints (1 roll of 90 m)

How the sum works

A 25 kg bag of multi-finish covers about 10 m² at 2 mm, so the calculator divides the area, plus waste, by the coverage and rounds up. For float and set it adds the backing coat: a 25 kg bag of hardwall covers about 3.2 m² at 11 mm and bonding about 2.7 m².

On plasterboard it adds scrim tape at about 1.25 m per m² of board for the joints.

Before you order

Coverage varies by brand and background, and suction changes how far a bag goes: check the bag or the maker's data sheet. Plaster has a shelf life, so check the date on the bag and keep it dry.

Guides that go with it

How do I do a quantity take-off from drawings?How to take off quantities from drawings for a small job: scale check, set order, deductions, waste and pricing, with a worked garden room example.What should I put in a quote for building work?What a quote for building work should say: scope, exclusions, drawings, price and VAT, validity, payment stages, dates, provisional sums and variations.How do you record daywork so you get paid for it?How to record daywork so it gets paid: get the instruction first, log labour, materials and plant each day, and get the sheet signed straight away.

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