Dot and Dab Calculator — Adhesive & Plasterboard Estimator

British Gypsum states that one 25kg bag of Gyproc Dri-Wall adhesive is enough for two standard 2400 × 1200mm boards under normal use — about 5.76 m² per bag. Knauf's plasterboard adhesive (Perlfix) covers roughly 4.6 m² per bag. The dabs should be roughly 50-75mm wide and spaced at 600mm centres horizontally, with three dabs per plasterboard width, plus a continuous ribbon along the top and bottom of each board. Allow more on uneven or out-of-plumb walls, which is where the wastage percentage helps.

Dot and dab (also called dry lining) is a method of fixing plasterboard directly to masonry walls using adhesive dabs. Blobs of adhesive (typically Gyproc Dri-Wall or Knauf Perlfix) are applied to the wall, then the plasterboard is pressed onto them and straightened with a spirit level. It is faster than traditional wet plastering and is the standard method for lining brick or block walls in UK new builds. For stud-framed dry lining systems, see our Dry Lining Calculator.

A dot and dab wall adds approximately 22-25mm to the wall thickness — roughly 10mm of adhesive gap plus 12.5mm of plasterboard. This is significantly thinner than a metal stud dry lining system. The gap between the wall and plasterboard also provides a small amount of insulation and allows for minor wall irregularities.

Dot and dab works best on solid masonry walls — brick, block, or concrete. The wall must be structurally sound, clean, and free from loose material. It is NOT recommended for damp walls (damp must be treated first), painted surfaces (unless scored), or stud partition walls (use screws instead). Use a suitable primer if the surface is very absorbent.

Divide your total wall area by the sheet area. A standard 2400 × 1200mm plasterboard sheet covers 2.88 m². For example, a wall that is 5m long and 2.4m high (12 m²) would need approximately 5 sheets, plus 10% wastage = 6 sheets. Always round up to the next whole sheet. Our Plasterboard Calculator can also help if you need to account for door and window openings. Once the boards are up, use our Plaster Coverage Calculator to work out how much multi-finish plaster you need for the skim coat — one 25kg bag covers 10 m² at 2mm.