Plastering Calculator
Calculate the quantity of plaster needed for any room or wall — from finishing skim over plasterboard to full two-coat work on solid walls.
Plastering Guide
Plaster Types
Finish plaster (skim): a thin 2–3mm layer applied over plasterboard or a flat base coat. Carlite Finish and British Gypsum Thistle Multi-Finish are the most common. Browning plaster: the standard base coat for brick and block walls before skimming. Applied 8–12mm thick. Higher porosity surfaces may need a second browning coat. Bonding plaster: used on low-porosity surfaces (concrete, dense block, painted surfaces) that do not absorb water enough for browning to adhere. One-coat plaster: suitable
Coverage Rates
Finish plaster (2–3mm): approximately 4–5 m² per 25kg bag. Browning (11mm typical): approximately 1.8–2.5 m² per 25kg bag. Bonding (8mm): approximately 3–3.5 m² per 25kg bag. One-coat (10mm): approximately 2.5–3 m² per 25kg bag. Always buy 10–15% more than calculated to allow for waste and ensuring you do not run short mid-room (different batches can have slightly different colour). Mix only as much as you can use in 30–45 minutes.
PVA Priming
PVA (polyvinyl acetate) bonding agent is essential before plastering. It seals porous surfaces to prevent them sucking water from the plaster too quickly (causing cracking), and provides a mechanical key. Apply diluted 1:5 (PVA:water) as a diluted primer, then a stronger 1:4 coat applied just before plastering — leaving it tacky rather than fully dry. Plasterboard needs light misting with water or a sealing coat of diluted PVA. Dense surfaces need a more concentrated PVA coat (1:3) or specialist
DIY vs Professional Plastering
Plastering is one of the more difficult DIY skills to master — achieving a truly flat finish takes significant practice. Professional plasterers charge £150–200/day plus materials, or £6–10 per m² for skim over plasterboard. A typical bedroom (40m²) costs £600–800 labour. For small patches, holes, and limited DIY plastering, the techniques are learnable. For full room replastering, especially if the final finish will be painted (which highlights every imperfection), consider using a professional
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