Grade II listed Hampstead master suite — Calacatta marble + LBC heritage retrofit

Brief

1820s Grade II listed end-of-terrace Georgian townhouse in Hampstead Village, NW3, within the Hampstead Conservation Area. Owner-occupier family of three. Existing master floor consisted of three small adjoining rooms — a 1950s-rebuild bathroom 4.5m², a small bedroom 9m² and a dressing area 4m² — none with heritage integrity. Brief: combine all three into a single master suite comprising a 14m² master ensuite + 8m² adjoining dressing room, retaining and restoring all original Georgian features including the rear sash window, cornicing, ceiling rose and original pine floorboards. Heritage-luxury specification — book-matched Calacatta Borghini marble, Drummonds + Lefroy Brooks heritage brassware, bespoke fluted walnut joinery.

Challenge

Five issues. (1) Listed Building Consent — works comprised removal of two non-original 1950s internal partitions, but the third partition concealed an original 1820s lath-and-plaster wall with cornice fragments; Camden conservation officer required heritage statement + measured survey + LBC application week 0. (2) Floor structure — combining three rooms onto one floor required removing two non-loadbearing partitions but also exposed undersized original Georgian joists (75×175 over 5m span) that would not take the Calacatta marble floor (45mm slab + adhesive + decoupling ~70kg/m² imposed load on top of the bath); structural engineer specified C24 sister joists 47×220mm in parallel + steel hangers. (3) Marble specification — book-matched Calacatta Borghini at this scale (28m² floor + 42m² walls) needed careful slab selection, vein-matching across 4 quarry runs, and full mock-up approval before fixing. (4) Steam shower — Mr Steam generator vented externally through a discreet brass cowl on a hidden parapet plant zone; conservation officer review required for the external vent. (5) Heating + cooling — listed-building constraints prevent open mechanical AC; underfloor heating + linear concealed cove + a discrete cassette behind reeded-brass grille was the agreed thermal solution.

Solution

Listed Building Consent application Camden Council week 0; pre-application meeting week -3 with Camden Conservation Officer and Hampstead Conservation Area Advisory Committee (CAAC). LBC granted week 18 with 9 conditions covering heritage statement adherence, weekly progress reports to conservation officer during enabling works, retention of original 1820s lath-and-plaster wall fragments, recording of all original features pre-strip, and approval-in-writing of marble specification mock-up. Build phase 14 weeks following LBC + Building Control. Weeks 1–3 enabling works + protection + recording. Original Georgian sash window protected with bespoke ply over-cover. Original pine floor lifted under conservation officer supervision, numbered, palleted for re-laying in a salvage-grade subset within the dressing room. Original 1820s lath-and-plaster wall fragments retained where possible behind new dry-lining. Weeks 4–6 structural — C24 47×220mm sister joists bolted to existing 75×175mm Georgian joists + new steel hangers to pocket details + acoustic insulation Rockwool Flexi 100mm between joists. Soil-pipe relocation internally via boxed chase through party-wall void (with Party Wall Award already issued and consented). Mr Steam generator (MS-150) installed in adjacent plant cupboard + 50mm flexible stainless duct routed to discreet brass cowl on rear parapet (conservation officer approved colour-matched bronze patination). Weeks 7–10 first fix + waterproofing. Schlüter-KERDI membrane over 22mm marine ply overlay bedded in epoxy + KERDI-DRAIN linear drain to walk-in steam shower. Underfloor heating Wunda 16mm low-profile wet UFH zoned across ensuite + dressing room + powered by retained Vaillant ecoFIT 935 system boiler. Weeks 9–12 marble fixing. Calacatta Borghini 20mm slab format 1200×600mm to floor + walls; book-matched bookend pattern across 4 quarry runs (Carrara region); full vein-mock-up approved by client + conservation officer week 7; fixed with Mapei Adesilex P10 white slow-set adhesive + epoxy grout + sealed Hydroshield 3-coat post-fix. Walk-in steam shower 2m × 1.2m with 10mm low-iron glass screen + Calacatta marble bench + Mr Steam controls + Lefroy Brooks Mackintosh aged-brass shower set with overhead rainshower + handheld + body jets. Drummonds Tay 1800mm cast-iron freestanding bath on Lefroy Brooks ball-and-claw aged-brass feet + Lefroy Brooks floor-mounted bath filler. Weeks 11–13 joinery + furniture. Bespoke his-and-hers fluted walnut vanity 2.4m wide + Calacatta Borghini worktop with integrated brass towel rails + reeded brass mirror cabinets above + integrated LED + downlight. Adjoining dressing room 8m² bespoke fluted walnut wardrobes + island chest + brass ironmongery + LED interior lighting on motion sensor + reclaimed original Georgian sash window restored in situ + Selectaglaze secondary glazing for acoustic + thermal. Brass concealed cassette AC behind reeded-brass grille in ceiling, vented externally through same parapet plant zone as steam vent. Heritage retention — cornice fragments retained + replicated where missing by Pavilion Plaster; ceiling rose retained; original pine floor re-laid in dressing room as salvage-grade feature. Week 14 commissioning + LBC discharge + Building Control final + handover.

Outcome

LBC discharged + Building Control final certificate issued week 14. Project completed Q1 2026, on programme. Master suite transformed from three undersized 1950s-modified rooms (17.5m² total) to a coherent 22m² master suite (14m² ensuite + 8m² dressing room) with heritage-luxury spec matching the rest of the recently restored townhouse. Resale agent (Goldschmidt & Howland Hampstead) valued the suite uplift at £285,000 against £165,000 spend = 173% gross ROI. Project featured in House & Garden Bathrooms June 2026 cover story, Drummonds case study Q3 2026, and Lefroy Brooks UK Heritage Bathrooms Awards 2026 finalist. Builderr first Grade II listed master-suite LBC project + first Calacatta Borghini book-matched bookend at 70m² scale + first Mr Steam steam shower in a listed building with conservation officer-approved external vent + first parallel LBC + Building Control + Party Wall Award delivery on a master-suite-only scope. Camden 4th portfolio case study + Hampstead first.