Grade II Georgian whole-house heritage restoration, Canonbury

Brief

A Grade II listed Georgian terrace (built 1825) in Canonbury, Islington — N1, Canonbury Conservation Area with Article 4 direction. The property: 178m² over four floors (basement, ground, first, second), three bedrooms, two reception rooms, original lower-ground kitchen and dining room. Listed grade II since 1972; key features include original lime-plaster cornices and ceiling roses (heavily over-painted), original pitch pine parquet (heavily worn), original mahogany staircase and handrail, original cast-iron fireplaces (three, all painted over), original front door with stained glass fanlight and side panels, original cast iron railings (Victorian replacement of original Georgian; partly missing from WW2 removal). Clients (retired barrister and architect spouse) purchased property at £2.4M with the express goal of bringing it back to historically authentic specification while integrating modern services discreetly. Listed Building Consent and Conservation Area planning required for all interventions.

Challenge

Five major heritage restoration challenges. (1) Listed Building Consent for whole-house intervention — Islington Council Conservation Officer involvement throughout; LBC application included 47-page heritage statement, photographic record of every original feature, method statement for each restoration intervention, conservation accreditation evidence for every specialist subcontractor. (2) Lime versus gypsum throughout — pre-1919 lime-plaster walls and ceilings throughout the property; any modern gypsum intervention would chemically destabilise original work; entire scope used NHL 3.5 lime-gauged plaster + sand mixes (sourced from Ty-Mawr Lime and St Astier). Specialist plasterers required (general plasterers not trained in lime work). (3) Cornice and ceiling rose replication in destroyed rooms — first-floor reception cornice destroyed in 1970s ceiling re-skim; second-floor bedroom ceiling rose lost; full run-in-situ lime-gauged replication required to match adjacent intact original. (4) Parquet restoration over solid concrete sub-floor — original pitch pine parquet over bitumen on Victorian concrete slab; significant cupping and lifting in five rooms from rising damp; required full removal, DPM retrofit (Sika SikaFloor EpoCem epoxy), and re-laying with reclaimed Victorian parquet to match original; sourced 38m² of period-correct reclaimed pitch pine from Hicks Joinery. (5) Stained glass front door restoration — original Victorian Art Nouveau stained glass in front door + fanlight + 2 side panels; 28% of glass broken or missing; restoration required period-matching glass sourcing from Holy Well Glass with specialist conservator coordination over 9-week workshop programme.

Solution

Pre-construction: Listed Building Consent approved at 14 weeks (full application + 21-day public consultation + Conservation Officer site visit + revised method statement); Planning Permission for area railings replication approved separately at 10 weeks. Heritage team appointed: lead conservation architect (RIBA Conservation Registered), specialist plasterer (Locker & Riley senior craftsman), stained glass conservator (Holy Well Glass), heritage joiner (Hicks Joinery), specialist fireplace restorer (London Fireplaces), specialist decorator (Sarah Frame Heritage Decoration). Builderr coordinated the heritage team as principal contractor with primary responsibility for programme, sequencing, and quality control. Programme. Weeks 1–4: enabling works — temporary roofs, scaffolding, sub-floor investigation, condition surveys. Weeks 5–12: hidden works — sub-floor DPM, electrical first-fix, plumbing first-fix, structural repairs (one cracked joist replaced in first-floor reception ceiling). Weeks 13–22: heritage restoration — cornice and ceiling rose work, fireplace restoration in three rooms, parquet relay (in 5 rooms over 3 weeks), staircase restoration. Weeks 23–28: decoration and finishing — specialist mineral paints (Edward Bulmer Natural Paint), period-correct colour scheme advised by conservation architect, stained glass reinstallation at week 26, area railings reinstalled at week 27. Specific specifications. Cornice: run-in-situ lime-gauged plaster in 3 rooms (28m + 32m + 36m linear metres = 96m total, £14,400 specialist labour over 4 weeks). Ceiling roses: 2 restored, 1 newly cast and installed. Fireplaces: 3 cast-iron register grates restored; chimneys swept and CCTV inspected; one stove install (Charnwood C-Four DEFRA-exempt, kitchen). Parquet: 38m² reclaimed pitch pine parquet relaid in 5 rooms over Sika EpoCem DPM; Osmo Polyx-Oil finish. Staircase: mahogany handrail paint-stripped, repaired, French polished; 28 cast-iron balusters cleaned and repainted in Crystal Palace Green. Stained glass: 4 panels (door, fanlight, 2 side panels); 3 panels restored in situ glass; 1 panel (left side) required complete rebuild with period-matching glass from Holy Well's salvage stock. Area railings: 5m of new cast iron railings replicated to match original (foundry: Castings of Whitchurch); set in lead in stone base; painted Crystal Palace Green.

Outcome

All heritage features fully restored or sympathetically replicated. Property valuation: pre-restoration £2.4M; post-restoration £3.45M (a £1.05M gross value uplift on £385,000 build cost — 273% ROI). EPC: D (61) → C (74) — improved by secondary glazing (Selectaglaze on 14 windows), loft insulation (sheep's wool, breathable), basement floor insulation. Listed Building Consent and Conservation Area planning sign-off achieved; Conservation Officer wrote letter of commendation for the project to be filed in the council heritage record. Project won 'Best Heritage Restoration London 2026' (Heritage London Awards). Press coverage in Country Life and Listed Heritage magazine. Clients fully occupied property from week 29; testimony from clients filed with Builderr as case study.