Ceilings, Cornices, and Plasterwork Guide for London Period Homes

ORIGINAL VICTORIAN CEILING PLASTER IN LONDON TERRACES WAS APPLIED IN THREE COATS ONTO RIVEN OAK OR SPLIT PINE LATHS (25X6MM APPROX, NAILED HORIZONTALLY TO THE UNDERSIDE OF THE FLOOR JOISTS WITH GAPS OF 6-8MM TO ALLOW THE PLASTER TO KEY THROUGH): (1) SCRATCH COAT (RENDER COAT): LIME PUTTY (SLAKED LIME) + COARSE SHARP SAND + ANIMAL HAIR (HORSE, COW, OR GOAT — TYPICALLY 25-30MM LONG, USED TO PREVENT SHRINKAGE CRACKING). MIXED APPROXIMATELY 1:2.5 (LIME:SAND) WITH HAIR ADDED AT APPROXIMATELY 1KG PER 100KG DRY MIX. APPLIED TO THE LATHS AT 8-10MM, SCRATCHED BACK WITH A SCRATCHER FLOAT TO PROVIDE KEY. (2) FLOAT COAT (STRAIGHTENING COAT): LIME PUTTY + FINE SHARP SAND + HAIR, 1:2 MIX, APPLIED AT 6-8MM TO EVEN THE BACKGROUND AND FLOAT LEVEL. (3) FINISH COAT (SETTING COAT): LIME PUTTY (UNFIBRED) + FINE CASTING SAND OR POZZOLANIC AGGREGATE (SOME LONDON PLASTERERS USED ITALIAN POZZOLANA POWDER FOR THE SETTING COAT TO ACHIEVE A HARDER SURFACE). APPLIED VERY THINLY (2-3MM) AND BURNISHED TO A SMOOTH FACE. THE SIGNIFICANCE OF HAIR PLASTER: LIME HAIR PLASTER IS FLEXIBLE AND MOVES WITH THE STRUCTURE — SURVIVING INTACT FOR 150+ YEARS IN MANY LONDON PROPERTIES WITHOUT CRACKING. CEMENT-BASED PLASTER (GYPSUM SAND/CEMENT UNDERCOAT) APPLIED DIRECTLY ONTO LIME HAIR PLASTER IS INCOMPATIBLE — DIFFERENTIAL MOVEMENT CAUSES CRACKING AND DELAMINATION. DIAGNOSTIC RULE: IF THE ORIGINAL PLASTER HAS A YELLOWISH-GREY COLOUR, VISIBLE HAIR FIBRES, AND A HOLLOW OR FLEXIBLE SOUND WHEN TAPPED — IT IS LIME HAIR PLASTER AND SHOULD BE RETAINED AND REPAIRED, NOT REPLACED.

THE VICTORIAN CORNICE IS THE DECORATIVE PLASTER MOULDING AT THE JUNCTION OF WALL AND CEILING. IN LONDON PERIOD PROPERTIES, ORIGINAL CORNICES WERE RUN IN SITU BY PLASTERERS USING A "RUNNING RULE" (A TEMPLATE CUT TO THE CORNICE PROFILE PULLED ALONG A FIXED SCREED TO PRODUCE THE CORNICE IN WET LIME PLASTER). ORIGINAL CORNICES ARE IRREPLACEABLE IF DESTROYED — MATCH EXACT PROFILE FOR ANY REPAIR. THREE OPTIONS FOR CORNICE REPAIR/REPLACEMENT: (1) IN-SITU LIME PLASTER REPAIR — THE CORRECT HISTORIC APPROACH FOR CONSERVATION AREA AND LISTED BUILDING WORK. A SKILLED SPECIALIST PLASTER RESTORER (MEMBERS OF THE BRITISH LIME ASSOCIATION OR CONTRACTORS LISTED BY SPAB — SOCIETY FOR THE PROTECTION OF ANCIENT BUILDINGS) CAN RUN NEW SECTIONS IN LIME PLASTER TO MATCH THE EXISTING PROFILE. THEY WILL PRODUCE A RUNNING RULE TEMPLATE FROM THE EXISTING CORNICE PROFILE AND APPLY SECTIONS IN NHL LIME PLASTER MATCHING THE ORIGINAL SPECIFICATION. COST: £150-£400 PER LINEAR METRE (SPECIALIST TRADE — EXTREMELY LABOUR-INTENSIVE). (2) GRG (GLASS REINFORCED GYPSUM) FIBROUS PLASTER — THE HIGHEST-QUALITY REPLACEMENT OPTION. GRG CORNICES ARE MANUFACTURED BY SPECIALIST SUPPLIERS (STEVENSONS OF NORWICH, CLARK & FENN, OR ARCHITECTURAL PLASTER UK) FROM A PROFILE MOULD CAST FROM AN ORIGINAL EXAMPLE. THE GRG MIX (GYPSUM PLASTER + ALKALI-RESISTANT GLASS FIBRE) PRODUCES A LIGHTWEIGHT, RIGID SECTION WITH HIGH DETAIL DEFINITION AND A DENSITY AND WEIGHT SIMILAR TO THE ORIGINAL PLASTER. GRG CORNICES ARE FIXED WITH CORNICE ADHESIVE (BRITISH GYPSUM THISTLE BONDING COMPOUND OR PLASTERMASTER CORNICE FIX) AND FINISHED IN JOINTING COMPOUND. COST: £20-£80 PER LINEAR METRE SUPPLY (DEPENDS ON PROFILE COMPLEXITY AND SUPPLIER). (3) POLYSTYRENE COVING — THE CHEAPEST OPTION (ANAGLYPTA OR HERITAGE PLASTER POLYSTYRENE COVING FROM £2-£5/LM SUPPLY). LIGHTWEIGHT, EASY TO FIT (ADHESIVE ONLY), BUT VISIBLE HOLLOW SECTION ON CLOSE INSPECTION AND LOW DETAIL DEFINITION. NOT APPROPRIATE FOR CONSERVATION AREAS OR LISTED BUILDINGS. ACCEPTABLE AS A BUDGET SOLUTION IN ROOMS WHERE PERIOD AUTHENTICITY IS NOT A PRIORITY.

ALONG WITH CORNICES, THREE OTHER PERIOD PLASTERWORK ELEMENTS ARE COMMONLY ENCOUNTERED IN LONDON VICTORIAN AND EDWARDIAN PROPERTIES: (1) CEILING ROSES — THE DECORATIVE PLASTERWORK FEATURE AT THE CENTRE OF THE MAIN RECEPTION ROOM CEILING (TYPICALLY IN THE FRONT RECEPTION ROOM AND REAR RECEPTION ROOM OF A VICTORIAN LONDON TERRACE). ORIGINAL CEILING ROSES ARE GRG OR RUN LIME PLASTER — TYPICAL VICTORIAN PATTERNS: SIMPLE ACANTHUS LEAF WITH EGG-AND-DART BORDER (SMALLER, C.1890-1910), COMPLEX FLORAL WITH ROPE MOULDING AND ANTHEMION (LARGER, C.1870-1890). REPLACEMENT: GRG FIBROUS PLASTER REPRODUCTION CEILING ROSES FROM STEVENSONS OF NORWICH (DESIGN 88, DESIGN 89, DESIGN 91) OR CLARK & FENN (CAVENDISH ROSE, BELGRAVIA ROSE) — SIZES FROM 300MM TO 900MM DIAMETER; £30-£300 SUPPLY DEPENDING ON DESIGN AND DIAMETER. (2) DADO RAILS — THE HORIZONTAL MOULDING AT APPROXIMATELY 900MM HEIGHT (WAIST LEVEL) THAT ORIGINALLY PROTECTED THE LOWER WALL FROM CHAIR BACKS. TIMBER DADO RAILS (PRIMED MDF OR SOLID PINE) FROM RICHARD BURBIDGE OR CHESHIRE MOULDINGS (OGEE, TORUS, OR CLASSIC PROFILES). FITTED WITH 50MM LOST-HEAD OVAL NAILS INTO TIMBER GROUNDS (FOUND BY STUD-FINDER) OR MIRRORFIX ADHESIVE PLUS PINS. (3) PICTURE RAILS — THE NARROW MOULDING AT APPROXIMATELY 1800-2000MM HEIGHT (JUST BELOW THE CORNICE) FROM WHICH PICTURES WERE HUNG USING PICTURE-RAIL HOOKS (AVOIDING HOLES IN THE WALLS BELOW). PRIMED MDF PICTURE RAILS (CHESHIRE MOULDINGS, B&Q OWN BRAND, TRAVIS PERKINS) FIXED IN THE SAME WAY AS DADO RAILS. IN PERIOD RESTORATION, ALL THREE ELEMENTS SHOULD BE PRESENT IN A CORRECTLY RESTORED VICTORIAN RECEPTION ROOM — THEY DEFINE THE PROPORTIONS AND CHARACTER OF THE SPACE AND ARE MISSING FROM MANY LONDON TERRACE RECEPTIONS THAT WERE STRIPPED IN THE 1970S AND 1980S.

FOR NEWLY BUILT ROOMS (LOFT CONVERSIONS, EXTENSIONS, GARAGE CONVERSIONS), NEW CEILINGS ARE CONSTRUCTED FROM PLASTERBOARD ON TIMBER OR METAL STUD CEILING GRID. THE CORRECT SPECIFICATION DEPENDS ON THE ROOM'S REQUIREMENTS: STANDARD CEILING (NON-FIRE, NON-ACOUSTIC): 12.5MM BRITISH GYPSUM GYPROC WALLBOARD ON TIMBER BATTEN CEILING (MINIMUM 47X47MM BATTENS AT 600MM CENTRES, SCREWED TO JOISTS OR CEILING RUNNER) OR METAL FURRING CHANNEL SYSTEM (BRITISH GYPSUM MF CEILING — METAL FURRING CHANNEL AT 600MM CENTRES, HANGERS FROM STRUCTURE). FIRE-RATED CEILING (BELOW A LOFT ROOM, LOFT CONVERSION STRUCTURE, OR HABITABLE FLOOR): 2X 15MM BRITISH GYPSUM GYPROC FIRELINE (GLASS FIBRE REINFORCED, FIRE RESISTANCE TO BS EN 520 TYPE F) — SCREW-FIXED TO CEILING GRID. GIVES 30 MINUTES FIRE RESISTANCE (REI 30) FROM BELOW. ACOUSTIC CEILING (BETWEEN FLOORS IN MULTI-STOREY BUILDING, LONDON APARTMENT): BRITISH GYPSUM GYPFRAME RESILIENT BARS (GRB 20) AT 400MM CENTRES, SUSPENSION FROM ACOUSTIC ISOLATION HANGERS (GENIECLIP LB OR KINETICS RIM), 2X 15MM GYPROC SOUNDBLOC — ACHIEVES Dw ≈ 45DB AIRBORNE AND LW ≈ 65DB IMPACT SOUND REDUCTION. PLASTER FINISH: STANDARD MULTI-FINISH PLASTER (BRITISH GYPSUM THISTLE MULTI-FINISH) — APPLIED IN 2MM WET PLASTER SKIM COAT AFTER BOARD SCRIM IS TAPED (50MM GYPROC JOINT TAPE OVER ALL JOINTS, BEDDED IN THISTLE BOARD FINISH). ALTERNATIVELY, DRY LINING TAPING AND JOINTING (BRITISH GYPSUM GYPROC EASYFILL OR BEADEX ULTRALIGHT FOR FLAT FINISH WITHOUT WET PLASTERING — INCREASINGLY POPULAR IN LONDON RENOVATIONS).

ORIGINAL LIME PLASTER REPAIR (SPECIALIST, PER M2): £80-£150/M2 FOR STRAIGHTFORWARD AREAS; £150-£300/M2 FOR CORNICE AND DECORATIVE WORK. CORNICE RESTORATION (IN-SITU LIME, SPECIALIST PLASTERER): £150-£400/LM. GRG CORNICE SUPPLY AND FIT (TYPICAL VICTORIAN PROFILE — STEVENSONS, 135MM PROJECTION X 120MM HEIGHT): £30-£60/LM SUPPLY + £15-£30/LM FIXING = £45-£90/LM TOTAL. POLYSTYRENE COVING SUPPLY AND FIT: £5-£15/LM. CEILING ROSE (GRG, 600MM DIAMETER, SUPPLY AND FIT): £100-£250. FULL CEILING REPLACEMENT (PLASTERBOARD AND SKIM, INCLUDING BOARD-FIX AND PLASTERBOARD): £15-£30/M2 (STANDARD BOARD + SKIM); £25-£50/M2 (FIRELINE OR ACOUSTIC). ACOUSTIC CEILING INSTALLATION (RESILIENT BAR SYSTEM — GENIECLIP): £40-£80/M2. DADO RAIL INSTALLATION (PINE PRIMED, MDF, 2M ROOM RUN): £80-£150. PICTURE RAIL INSTALLATION: £80-£150 PER ROOM. FULL RECEPTION ROOM PERIOD RESTORATION (CORNICE GRG, CEILING ROSE, DADO RAIL, PICTURE RAIL, ORIGINAL PLASTER REPAIR, DECORATED): £2,000-£5,000 PER ROOM DEPENDING ON ROOM SIZE, CORNICE COMPLEXITY, AND EXTENT OF REPAIR NEEDED.