Heritage breathable finishes
Lime render + limewash: traditional pre-1920s construction relies on breathable lime mortar + render + limewash; allows building fabric to breathe — moisture evaporates from masonry naturally; prevents trapped moisture causing internal damp + structural decay. Modern cement render + acrylic paint on heritage wall: traps moisture inside masonry; classic cause of internal damp in Victorian/Edwardian + Georgian houses after misguided 1970s/80s 'modernisation'. Lime render application: 2-coat lime + sand 20–30mm total thickness on prepared masonry; cure 28+ days before limewash. Limewash: 3–5 thin coats (looks watery during application; develops opacity + colour as carbonates with air over weeks). Colour: natural earth pigments (ochre, umber, charcoal, brick red, ivory, taupe) — limited heritage palette. Cost: lime render £45–£125/m² supplied + applied; limewash £25–£55/m² (3 coats); specialist installer (Lime Stuff, Tomahawk, Ty-Mawr) experienced in heritage spec essential. Mineral / silicate paint (Keim, Beeck): modern alternative to limewash — bonds chemically to mineral substrate (lime render + sand-cement render + brick + concrete); breathable; 25+ year life on properly prepared substrate; wide colour palette. Application: 2 coats over Keim Concretal Lasur primer (sealer + binder); spray + brush; £35–£95/L paint + £25–£75/m² install = £55–£135/m² supplied + applied. Best for: Conservation Area properties + Listed Buildings + sympathetic restoration where breathability essential; modern alternative achieving heritage performance + lower maintenance vs limewash.
Modern masonry paint
Acrylic masonry paint (Dulux Weathershield, Sandtex 10-Year, Crown Trade Weathercoat, Wickes Cover-All): water-based + film-forming on masonry; 10–15 year life on properly prepared substrate; durable + colour-stable. Cost £25–£55/L (5L covers ~30m² 2 coats); install £18–£35/m² supplied + applied (£50–£90/m² total typical 3-bed elevation). Best for: 1930s+ properties with cement render substrate (acrylic appropriate match — not heritage breathable spec); modern extension; uPVC + composite cladding overpaint; rendered new-build. Avoid: pre-1920s heritage construction where breathable finish required. Pliolite-based exterior paint: solvent-based, deeper penetration into masonry, better grip on weathered surface; £35–£75/L; preferred for refurbishment of heavily weathered or contaminated masonry; durable 10–18 year life. Silicone-based render paint (K-Rend, Marmorit, EWI Pro): part of premium render system — pre-coloured silicone-cement render with self-coloured finish (no separate paint layer); 25+ year colour stability; breathable; £125–£245/m² supplied + applied for full render system. Best for: new-build extension + insulated render system (EWI — external wall insulation finished with silicone render); premium spec rendered extension. Lifetime + value: silicone render highest premium + longest life; mineral paint mid-premium with heritage compatibility; acrylic masonry value spec for modern construction.
Specification at planning + Conservation
Conservation Area + Listed Building: exterior finish + colour subject to Conservation Officer approval — heritage breathable + heritage colour palette typically required (limewash, mineral paint Keim) in heritage tones (Wevet, Wimborne, ochre, charcoal). Acrylic + cement render on Listed Building: refused without specific justification (modern materials damage heritage fabric). Specify at planning application + heritage statement; sample area approved by Conservation Officer before full application. Non-heritage areas: wider material choice — modern acrylic + silicone render acceptable; colour palette unrestricted (avoid jarring contemporary colours in established residential streets — Conservation Officer may object even outside CA). Cost: heritage spec (lime render + limewash, Keim mineral paint) 1.5–3× cost of modern acrylic masonry equivalent; budget at design + planning stage. Maintenance schedule: limewash 5–8 year recoat; Keim mineral paint 15–25 year recoat; acrylic masonry 10–15 year recoat. Heritage spec lower whole-life maintenance cost despite higher upfront — fewer recoats + better fabric protection. Builderr default heritage spec: Keim Concretal-A or Keim Soldalit on existing render + 2 coats on prepared substrate; Conservation Officer engaged at early design; sample wall approved before scope. Modern extension default: Dulux Weathershield Smooth Masonry + Sandtex Fine Textured for traditional look, K-Rend silicone render system for contemporary.
