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Internal · boards · plaster
How many plasterboards, and how much plaster?
Boards, fixings and finish plaster for walls and ceilings. Dot-and-dab and screw-fixing use completely different fixings, so it asks which.
1
Measure it
Every box has its own unit next to it.
Change the unit beside any box and the number converts. The (i) beside each question says what the box wants and where the figure usually comes from. Anything marked per cent is a percentage of the quantity above it.
2
Check the rates
Rates and assumptions used
These are the figures the calculator works to. Change any of them and the order list updates — your merchant’s pack sizes and your own waste allowances beat the defaults every time.
How this one works
Boards = total area × (1 + waste %) ÷ sheet area
Dot and dab: adhesive by the bag per board. Screw fix: screws at 300 mm centres
Plaster coverage scales with thickness: 10 m² a bag at 2 mm becomes 6.7 m² at 3 mm
The figures the calculator works to. Every one can be changed in step 2, and your merchant’s pack sizes and your own waste allowances beat these defaults every time.
Rate
Default
Why
Adhesive per board
5.5 kg
Roughly a third of a bag per board on a flat wall.
Adhesive bag
25 kg
Screws per board
35 no.
At 300 mm centres.
Scrim per board
9 m
Plaster coverage
10 m²/bag
25 kg multi-finish at 2 mm. The calculator scales this for the thickness you set.
PVA coverage
8 m²/L
Water per bag
11 L
A worked example
With the defaults the page opens on:
How much wall? 58 square metres
How much ceiling? 24 square metres
Dab or screw? Dot & dab onto masonry
Which board size? 2400 × 1200 — 2.88 m²
How thick is the skim? 3 millimetres
Spare for cuts 10 per cent
Boarding
Total area: 82 m² — 58 m² wall + 24 m² ceiling
Board waste: 10 %
Boards: 32 sheets— 2.88 m² each
Adhesive: 8 × 25 kg bags— 176 kg at 5.5 kg a board
Scrim tape: 288 m
Corner beads: 10 × 2.4 m — rough count — check it against your corners
Skim
Coverage at 3 mm: 6.7 m²/bag
Multi-finish: 13 × 25 kg bags
PVA: 11 litres
Water: 143 litres — about 11 L a bag
Change any figure above and every line recalculates; the small print under each row is the sum that produced it.
Questions people ask
How many plasterboards do I need?
Total area × waste ÷ sheet area. 58 m² of wall and 24 m² of ceiling at 10% waste needs 32 boards at 2.88 m² (2400 × 1200).
How much plaster per board?
The calculator works coverage from thickness: a 25 kg bag of multi-finish covers 10 m² at 2 mm, so 6.7 m² at 3 mm. It shows the coverage row for the thickness you set and the bags from that.
Dot and dab or screw?
Dab needs adhesive - about 5.5 kg a board, a third of a bag. Screwing needs 35 drywall screws a board at 300 mm centres. They are not interchangeable, so the calculator asks which.
Read before you order. These work out quantities, not structural design — spans, lintels, rebar and foundation depths need an engineer and Building Control sign-off. Waste allowances are defaults, not promises: awkward cuts, long runs and bad weather all eat more than 5%. Where a merchant sells whole packs, the figure is rounded up to whole packs.
