plastering techniques

Quick Answer: Skimming plaster (also called skim coating) involves applying a thin 2-3mm layer of finishing plaster over plasterboard, old plaster, or prepared surfaces to create a smooth, paint-ready finish. Using multi-finish gypsum plaster, professional plasterers typically complete a room in 1-2 days, with surfaces ready to decorate after 5-7 days of drying. The technique requires specific tools (laying-on trowel, water spray, hawk), proper mixing ratios (add plaster to water, never reverse), and two-coat application with precise timing between coats. Expect to pay £15-25 per m² for professional skimming in 2026. What Is Skimming Plaster and Why It Matters Skimming plaster represents the final, most visible stage of plastering work — the difference between a professional finish and an amateur job. When done correctly, skimming creates a perfectly smooth, flat surface that accepts paint, wallpaper, or decorative finishes without visible imperfections. In the UK construction industry, skimming typically refers to applying British Gypsum Multi-Finish plaster (or equivalent products like Thistle Board Finish) in two thin coats totalling 2-3mm thickness. This differs from rendering (external cement work) or floating (thicker backing coats). Professional plasterers spend years mastering this skill. The technique demands precise timing, consistent mixing, and the ability to “read” the plaster as it sets — skills that separate competent tradespeople from cowboys. When You Need Skimming: Common Scenarios Homeowners and contractors commission skimming work in several situations: New plasterboard installations: After fitting 12.5mm plasterboard, the joints and surface require skim coating for a uniform finish Renovation projects: Damaged or dated textured walls (Artex, woodchip) need skimming after preparation Post-rewire or replumb work: Chased walls and filled channels require skimming to restore the surface Covering old lime plaster: When retention is possible, skimming over bonding coat provides a modern finish New extensions or loft conversions: Fresh stud walls need complete plastering including skim coat Damp repair completion: After remedial work and replastering with sand/cement, skimming provides the final surface Pro Tip: Never skim directly onto painted surfaces, glossy plasterboard, or dusty substrates. The plaster won’t bond properly and will likely crack or detach within months. Always assess the substrate first — sometimes bonding coat, PVA solution, or Blue Grit preparation is essential. Essential Materials for Skimming Plaster Professional results demand quality materials. Here’s what you’ll need: Plaster Selection Product Best For Setting Time Price (25kg) British Gypsum Multi-Finish Most surfaces, general purpose 90-120 minutes £8-11 Thistle Board Finish Plasterboard only 90-120 minutes £8-11 Knauf MP75 Machine application Variable £9-12 Speedskim One-Coat DIY, small repairs 60-90 minutes £12-15 Coverage rates: One 25kg bag covers approximately 10-13m² at 2mm thickness. Professional plasterers calculate 2.5kg per square metre for two-coat work, plus 15% wastage. Substrate Preparation Materials PVA bonding solution: Unibond or similar (£8-12 per 5L) — dilute 1:4 with water for most applications Blue Grit bonding agent: For painted surfaces or difficult substrates (£18-25 per 5L) Scrim tape: 50mm self-adhesive mesh for plasterboard joints (£3-5 per 90m roll) Joint filler: Gyproc EasiJoint or similar for deep gaps (£6-9 per 5kg tub) You can source these materials from Screwfix, Wickes, or specialist suppliers like Travis Perkins. Trade accounts typically offer 10-15% discount on list prices. Tools Required for Professional Skimming Quality tools make an enormous difference. Here’s the complete kit: Core Plastering Tools Laying-on trowel: 14″ or 16″ high-carbon steel (Marshalltown, Refina, or Nela — £35-75) Finishing trowel: 11″ or 13″ for second coat (£25-55) Hawk: 12-13″ aluminium or magnesium (£15-35) Mixing paddle: 120mm spiral mixer for drill (£8-15) Corded drill: Minimum 850W, variable speed essential (£60-120) Mixing buckets: Flexible rubber buckets, 25L capacity (£8-12 each — buy 3-4) Water spray bottle: Fine mist sprayer (£4-7) Spot board: 600mm x 600mm board on stand (£25-45 or DIY with ply) Spirit level: 1200mm for checking flatness (£20-45) Plasterer’s brush: For damping and cleaning (£6-12) For detailed guidance on selecting the best tools, consult our complete guide to plastering trowels. Safety Equipment Don’t overlook protection — gypsum dust causes respiratory irritation and eye damage: FFP2 or FFP3 dust masks (£1.50-4 each) Safety goggles or glasses with side protection Dust sheets and polythene floor protection Work boots with steel toe caps Cotton or latex work gloves (gypsum is alkaline and dries skin) Professional plasterers maintain comprehensive safety equipment — learn more in our guide to plasterer safety equipment. Step-by-Step Skimming Technique Here’s how professional plasterers achieve that perfect finish: Stage 1: Surface Preparation (Critical) Never rush this stage. Poor preparation causes 80% of skimming failures. Clean the surface: Remove all dust, grease, paint flakes, and loose material with a stiff brush Fill major defects: Use bonding plaster for deep holes (over 6mm), joint filler for smaller gaps Apply scrim tape: Cover all plasterboard joints with self-adhesive mesh tape, pressing firmly Seal the substrate: Apply diluted PVA (1:4 ratio) with a brush or roller — two coats for very absorbent surfaces Check PVA timing: Wait until tacky but not fully dry (usually 20-30 minutes depending on temperature) ⚠️ Warning: If PVA fully dries before you apply plaster, it creates a sealed surface that repels water. The plaster won’t bond and will slide off the wall. If this happens, apply another PVA coat and time it correctly. The substrate should feel slightly sticky when you start plastering. Stage 2: Mixing the Plaster Consistency determines workability and final quality. Professional plasterers achieve this through precise technique: The correct mixing sequence: Fill a clean bucket with approximately 10-12 litres of cold, clean water Add plaster gradually, sprinkling it evenly across the water surface Continue adding until plaster forms an “island” just above water level Wait 30-60 seconds for absorption (no stirring yet) Mix thoroughly with paddle at low-medium speed (400-600 RPM) for 2-3 minutes Scrape down bucket sides and mix briefly again Target consistency: Thick double cream or soft butter — the plaster should drop slowly from the trowel, not run off or stick stubbornly. Common mixing mistakes include adding water to plaster (creates lumps), over-mixing (accelerates setting), and contaminated equipment (old plaster fragments speed setting dramatically). Stage 3: