Plasterboard
Dot and dab adhesive bags and dabs per board
- where
- bags of adhesive needed, unrounded
- wall area to dry line (m²)
- waste allowance (%)
- coverage per bag from the datasheet (m²)
- whole bags to buy
- adhesive needed (kg)
- bag weight (kg)
- dabs per board
- vertical rows of dabs per board
- board height (mm)
- dab centres down each row (mm)
Explain this equation
This works out bags of plasterboard adhesive for dot and dab dry lining, and how many dabs go on each board. Use it when pricing a dry-lining job on masonry walls.
C is the manufacturer’s coverage per bag (about 4.6 m² for Knauf Drywall Adhesive). A is the wall area and w the waste. For the dabs, r is the number of vertical rows across the board, H the board height and d the spacing of dabs down each row.
Adhesive is estimated by area like any coverage figure, then rounded up to whole bags. The dab count is rows times dabs per row, with dabs per row being the board height divided by the spacing, rounded up so the top and bottom are supported.
Sense check: a 30 m² room is about 6.5 bags before waste, so seven or eight bags. A 2400 mm board with three rows at 300 mm takes 24 dabs.
Watch out: the dab count excludes the continuous bands at top, bottom and round openings and services, which use extra adhesive. Very uneven walls need deeper dabs and more adhesive.
Bags of plasterboard adhesive for dot and dab dry lining, and the number of dabs to put on each board.
Enter your values to see the result.
Good to know
Knauf Drywall Adhesive is published at about 4.6 m² per 25 kg bag for dot and dab; British Gypsum DriWall Adhesive gives no area figure but requires at least 20% contact between board and background (BS 8212). NHBC: dabs 50–75 mm wide and about 250 mm long at 300 mm centres vertically, 3 vertical rows per 1200 mm board for 12.5 mm and 15 mm board (4 for 9.5 mm), plus a continuous band at the top and bottom and around openings and services. Uneven or very suctive walls use more adhesive.
Common mistake
Leaving out the continuous perimeter band and the bands round sockets and windows. They stop air leaking behind the board and are needed for airtightness and fire-stopping.
Limits
Coverage depends on how far the background is out of plane (dab depth). The dab count is for the field of the board only.
Sources
- Knauf Drywall Adhesive technical sheet (coverage 4.6 m² per 25 kg bag, dot and dab; dabs 50–75 mm wide × ~250 mm long)
- British Gypsum, Gyproc DriWall Adhesive product data sheet (14 L water per bag; 20% minimum contact per BS 8212)
- NHBC Standards 9.2.4 Dry lining (Table 7 screw centres; Table 9 adhesive dabs 50–75 mm × 250 mm at 300 mm centres, 3 rows per 1200 mm board for 12.5 mm)
- British Gypsum, BS sub-clauses (screws at max. 300 mm centres on walls, 230 mm on ceilings; 10 mm from bound edges, 13 mm from cut edges; dabs ≥ 20% contact)
Results are calculations from the published methods and manufacturer figures shown, and depend on the data you enter. Always follow the manufacturers’ system and product data, BS 8212, BS EN 13914 and Building Regulations. Coverage rates vary by product, background and thickness. Check prices, VAT and CIS rules with your own records and HMRC.