Common London stone types + decay patterns
London stone types in residential use: (1) Portland (Dorset Jurassic limestone) — Belgravia, Mayfair, Marylebone, Regent's Park stucco terraces, City of London Georgian/Victorian commercial conversions. Pale cream, fine-grained, durable but soft to weather + acid rain. Decay: surface dissolution from acid rain (post-1960s), salt damage, biological growth, mortar joint failure. (2) Bath stone (Somerset oolitic limestone) — Bayswater, Kensington Georgian + Victorian classical terraces. Honey-cream, very soft + porous. Decay: blackening from carbon, salt crystallisation, severe spalling on exposed elevations + parapets. (3) York stone (Yorkshire sandstone) — chimney cappings, paving, hearthstones, Victorian terrace lintels + sills, banking + civic buildings. Buff to pale grey, durable + weather-resistant. Decay: less common, mostly mechanical damage + iron staining. (4) Kentish Ragstone (Kent sandstone) — Victorian Gothic, civic + church work, mansion blocks. Grey-green, hard + durable. Decay: limited, mostly mortar joint failure + green algae. (5) Granite — door steps, plinth courses, banking facades. Cornish + Scottish granite very durable, rarely needs restoration except polishing or recutting. Decay diagnosis: thermal imaging + sample core analysis by Stone Federation member (£180–£480 per diagnosis report) before repair specification. Common pre-repair scope: jet-clean diagnosis impossible until cleaned (see [[brick-cleaning-restoration-london-cost]]) — sequence is clean first, then assess + repair, then consolidant if needed.
Repair methods + cost + LBC + specialist contractors
Repair methods 2026: (1) Indent — cutting out decayed stone block + replacing with new dimensional stone matched for type, colour, grain direction. £180–£420 per block supply + fit + scaffold-separate. Best for: significant face loss, structural blocks, cornice + parapet. Stone supply Cliveden + Stonewest stockholding + custom quarry orders. Lead 4–10 weeks. (2) Plastic repair — proprietary lime + stone-dust mortar (St Astier Plastic Repair, Lithomex, Pavilion Plaster mix) applied to repair surface decay + lost detail. £85–£180/m² for spread repairs; £140–£420 per discrete defect. Best for: minor surface loss, weathered detail, areas where indent uneconomic. Limitation: visible after 5–8 years as plastic ages differently to host stone. (3) Stone consolidation — Wacker BS 290 / Funcosil silicate consolidant penetrating + binding decayed surface, £45–£120/m² applied. Reversible + non-visible. Used post-cleaning on lightly weathered Portland + Bath stone. (4) Mortar joint repointing — see [[lime-mortar-vs-cement-pointing-london]] — lime mortar mandatory on heritage stonework. (5) Full carved replacement (cornice, capital, baluster, finial) — £450–£1,800 per element supplied + fitted, plus £180–£420 carving from master mason. 8–18 week lead. LBC: every external stone repair on Grade I/II/II* listed requires LBC — method statement + sample + repair register required. CA: pre-application advice + photographic record submission usually adequate. Specialist contractors London: Cliveden Conservation, Owlsworth IJP, Stonewest, Szerelmey (Civic Specialist), Sally Strachey Historic Conservation, Pavilion Plaster — Builderr panel of vetted specialists, all Stone Federation members + RIBA Conservation Architect ARB / CSCS Heritage Skilled. Insurance: specialist £5M+ PI standard. VAT: 0% LBC qualifying repairs on Grade I/II*; 20% otherwise. Common scope on Belgravia / Mayfair Portland stone terrace front: cleaning + indent repairs + plastic repair + consolidant + lime repointing + scaffold + LBC fees — £45,000–£140,000 typical façade restoration.
