Plasters: Types & Costs
Interior plasters (walls/ceilings)
Gypsum plaster (powder) – standard interior
- Best for: Dry rooms. Pros: Smooth, fast set, easy sanding. Cons: Not for damp.
- Cost vs baseline (Gypsum = 0%)
- Ready-mix polymer skim: +20–60% (fewer defects, longer open time)
- Cement-based interior (wet areas): +10–35%
- Lime / lime-gypsum (breathable): +15–40%
- Clay plaster (natural, hygroscopic): +30–80%
- Venetian/plaster stucco (polished lime): +120–250%
When to use
- Wet rooms/kitchens: Cement-based skim (then waterproofing/tiles/paint).
- Heritage/breathable masonry: Lime/lime-gypsum or clay.
- Premium decorative: Venetian/polished lime.
- Fast, smooth refits: Ready-mix polymer skim.
Exterior renders (façades)
Cement–lime render (traditional) – base reference
- Best for: General façades, robust base for paint/finish coat.
- Pros: Tough, widely available. Cons: Needs curing; can micro-crack if not detailed.
Monocouche (through-colour cement render)
- Pros: One-coat, coloured through, scraped finish. Cons: Junction cracking if detailing is poor.
- Cost vs baseline (Cement–lime = 0%): +20–50%
Thin-coat systems (final coat over basecoat/ETICS)
- Acrylic (organic): Very flexible, big colour range; lower vapor openness. +10–30%
- Silicone/siloxane: Self-cleaning, water-repellent, good UV; balanced vapor. +20–45%
- Silicate (mineral): Highly vapor-open, mineral look; needs mineral substrates/primers. +15–40%
Mineral basecoats (cementitious)
- Machine-applied base + mesh; then thin-coat finish. +5–20% vs cement–lime (for base layer)
Specialty
- Insulating/thermal plasters (perlite, aerogel): Adds R-value, light but pricey; not a substitute for ETICS thickness. +80–200%
- Pebble-dash/stone-dash: Very durable; rustic aesthetic. −10–+10% (materials vary)
Performance highlights
Interior
- Smoothness: Gypsum & polymer skim = best finish.
- Moisture tolerance: Cement ▶ Polymer ▶ Gypsum; Lime/clay are breathable (not water-resistant).
- Breathability: Clay/Lime ▶ Gypsum ▶ Polymer ▶ Cement.
- Repairability: Gypsum/Polymer easiest; Venetian needs skilled touch-ups.
Exterior
- Crack resistance: Silicone/acrylic thin-coat (on mesh) ▶ Monocouche ▶ Cement–lime.
- Vapor openness: Silicate ▶ Silicone ▶ Acrylic.
- Self-cleaning: Silicone/siloxane best.
- Colour stability: Mineral/silicate and quality silicone hold colour well.
Pros & cons (quick)
Gypsum (int.)
- Smooth, fast, economical | − Not for damp
Polymer ready-mix (int.)
- Flexible, fewer pinholes | − Longer dry, higher material %
Cement-based (int./ext.)
- Hard, moisture/frost tolerant | − Harder to sand; can shrink if rushed
Lime / Clay (int.)
- Breathable, healthy interiors | − Lower hardness; skilled application
Venetian (int.)
- Luxury finish, depth | − High skill/cost
Cement–lime render (ext.)
- Robust, universal | − Needs curing; may micro-crack
Monocouche (ext.)
- One-coat, coloured | − Sensitive at joints/details
Acrylic thin-coat (ext.)
- Flexible, many colours | − Lower vapor openness
Silicone/siloxane thin-coat (ext.)
- Water-repellent, self-cleaning | − Higher material %
Silicate thin-coat (ext.)
- Mineral, vapor-open | − Strict substrate/primer rules
Risks & how to avoid
- Substrate movement / cracks (ext.): Add reinforcement mesh in base; respect movement joints.
- Blistering/peeling: Wrong primer or damp substrate. Fix: moisture tests, correct primers, curing times.
- Salt efflorescence: Trapped moisture/salts. Fix: capillary breaks, breathable systems (silicate/lime) where needed.
- Mould (int.): Low breathability + humidity. Fix: ventilation, breathable plasters/paints in problem rooms.
- Colour mismatch (ext. thin-coats/monocouche): Batch variation. Fix: order one batch; mix pails; keep wet edge.
Quick choice guide
- Interior, dry & smooth: Gypsum or Polymer skim
- Interior, breathable/heritage: Lime or Clay
- Interior, wet-prone zones: Cement-based (then waterproof/finish)
- Exterior, durable & clean: Silicone thin-coat over reinforced base
- Exterior, mineral & vapor-open: Silicate thin-coat
- Exterior, one-coat with colour: Monocouche
- Need added insulation in a thin layer: Thermal plaster (understand limits)
