Grade II listed full renovation, Pimlico

Brief

A four-storey Grade II listed Georgian terrace in Pimlico — mid-terrace, SW1V, within the Churchill Gardens and Grosvenor Estate Westminster conservation areas. The property had been subdivided into two flats in the 1970s and was being returned to single-family occupation. Brief: full structural and fabric restoration, kitchen-dining ground floor renovation, all 14 sash windows draught-proofed and reglazed, new M&E throughout, and smart home infrastructure installed behind period-appropriate finishes.

Challenge

Westminster City Council's Conservation Area Advisory Committee (CAAC) and Historic England's local advisors apply the most stringent LBC conditions in England — a 14-week pre-construction programme. The 1970s subdivision had introduced a concrete block party-floor between the ground and first floor that was not original to the building — removal required a structural engineer's justification and an LBC amendment that took 6 additional weeks. All 14 sash windows were single-glazed; double glazing is not permitted in Westminster Grade II sash windows — draught-proofing (Ventrolla spring seal + pile weatherstrip) and secondary glazing (Selectaglaze Series 10, 6mm optifloat glass) were the LBC-compliant solutions. The M&E routing challenge: running Cat6, speaker cable, CCTV, and heating pipework through solid Georgian masonry with 600mm stone and brick walls, original lath-and-plaster throughout — no chasing permitted.

Solution

LBC applications: submitted two — one for the structural removal of the non-original concrete block floor (approved with condition that lintels over the original ground-floor fireplace openings be retained and exposed); one for M&E routes (approved with condition that all new penetrations through external walls use lime mortar pinning and be reversible). Structural: the concrete floor slab (120mm unreinforced) was broken out by hand (no vibration tools near the listed fabric); the original timber floor structure beneath, though degraded, was partially salvageable — 60% of original joists retained, 40% sistered or replaced with new Douglas fir matching the original section. Kitchen: ground floor retained its original Regency room sequence (front parlour and rear kitchen) with a connecting opening formed in the non-load-bearing partition — not open plan, but connected. LBC condition was satisfied: no original fabric was removed. Sash windows: Ventrolla spring-seal draught-proofing installed to all 14 sashes (no drilling, no adhesives to original woodwork); Selectaglaze Series 10 secondary glazing fitted to all ground and first floor windows — achieving an effective U-value of approximately 1.8 W/m²K on the secondary-glazed units (from 4.8 W/m²K single-glazed baseline). M&E routing: all new cabling run in timber-lined vertical service risers built within original cupboard spaces and floor voids; no horizontal chasing through lime-plastered walls. Smart home pre-wire included Cat6 to every room, speaker cable to kitchen and living room, Lutron HomeWorks QS first-fix cabling.

Outcome

Four-storey full renovation completed in 22 weeks. The property returned to single-family occupation — 4 bedrooms, 3 bathrooms, double-height ground floor reception. LBC conditions complied with in full; Westminster conservation officer's post-completion visit recorded the project as a reference for reversible M&E routing in Grade II listed properties. Secondary glazing and Ventrolla draught-proofing reduced draughtiness by 78% (measured by blower door test pre and post); EPC improved from F (29) to D (62) — the maximum achievable on a Grade II listed property in Westminster without a fabric-compromising intervention. Smart home commissioning: Lutron HomeWorks QS for lighting throughout (14 zones), Sonos in-ceiling in kitchen and lower ground, CCTV (4 cameras), Ajax alarm system. Programme 22 weeks build, 36 weeks total including LBC.