Pitched Roof Repair for London Victorian Terraces: From Single Tiles to Full Re-Roof

ORIGINAL PLAIN CLAY TILES ON LONDON VICTORIAN TERRACES: - PLAIN CLAY TILES ARE THE STANDARD COVERING ON LONDON VICTORIAN TERRACES FROM APPROXIMATELY 1880 ONWARDS. THE ORIGINAL TILES ARE HAND-MADE OR MACHINE-PRESSED CLAY TILES: 265MM × 165MM (THE STANDARD UK PLAIN TILE SIZE — THE ONLY SIZE THAT HAS REMAINED BROADLY CONSISTENT FROM VICTORIAN TO MODERN). TWO NIBS ON THE BACK FACE HOOK OVER THE TILE BATTEN; NAILED EVERY 4TH COURSE (NAILING EVERY COURSE — "EVERY TILE NAILED" — WAS NOT STANDARD IN ORIGINAL VICTORIAN CONSTRUCTION). THE TILE IS SINGLE CAMBERED (SLIGHTLY CURVED ALONG ITS LENGTH — THE CURVE ENSURES THAT THE LOWER EDGE OF EACH TILE IS LIFTED SLIGHTLY AWAY FROM THE FACE OF THE TILE BELOW, ALLOWING DRAINAGE AND PREVENTING CAPILLARY ACTION). - TYPES OF ORIGINAL TILE (COMMONLY FOUND ON LONDON VICTORIAN TERRACES): - HANDMADE CLAY TILE (PRE-1900): IRREGULAR SURFACE, SLIGHTLY VARIED COLOUR AND PROFILE. OFTEN MORE VALUABLE FOR CONSERVATION REASONS THAN MACHINE-PRESSED. - MACHINE-PRESSED CLAY TILE (1890S+): MORE UNIFORM BUT STILL NATURAL CLAY — TYPICALLY DARK RED OR BUFF. - SAND-FACED CLAY TILE (1890S-1940S): A MACHINE-PRESSED TILE WITH A SAND TEXTURE APPLIED TO THE FACE — PROVIDES A TEXTURED APPEARANCE AND IMPROVES RESISTANCE TO ALGAE GROWTH. - CAMBER AND FITTING: PLAIN TILES MUST BE FITTED WITH THE CORRECT CAMBER ORIENTATION — CURVE UPWARD (CONCAVE FACE DOWN). A TILE FITTED UPSIDE DOWN SITS FLAT, CUPS WATER, AND WILL FROST-CRACK.

COMMON DEFECTS IN PLAIN CLAY TILE ROOFS: 1. CRACKED OR BROKEN TILES: IMPACT DAMAGE (FALLING CHIMNEY POTS, FALLING TILES FROM ABOVE, PERSONS WALKING ON THE ROOF WITHOUT BOARDS). ALSO: FROST CRACKING (TILES THAT WERE NOT FIRED TO A SUFFICIENT TEMPERATURE TO ACHIEVE LOW WATER ABSORPTION — < 0.5% WATER ABSORPTION BY WEIGHT IN A FROST-RESISTANT TILE; TILES WITH HIGHER WATER ABSORPTION CRACK ON FREEZING WHEN WET). ORIGINAL HAND-MADE AND MACHINE-PRESSED CLAY TILES ARE GENERALLY FROST-RESISTANT IF ORIGINALLY WELL-FIRED. 2. SLIPPED TILES: A TILE HAS SLID DOWN THE SLOPE (THE NIBS HAVE DISENGAGED FROM THE BATTEN — DUE TO THE BATTEN SHRINKING, DECAYING, OR THE TILE BEING CRACKED AT THE NI). SLIPPED TILES LEAVE A VISIBLE GAP AND EXPOSE THE SARKING MEMBRANE OR LATH AND PLASTER (ORIGINAL) TO UV AND WIND. 3. MOSS AND LICHEN GROWTH: VERY COMMON ON NORTH-FACING SLOPES AND IN SHADED AREAS — MOSS RETAINS MOISTURE AND ACCELERATES TILE FREEZE-THAW DAMAGE. BIOCIDE TREATMENT (BATICLEAN CR, ALGAECLEAR PROFESSIONAL): SPRAY ON; ALLOW MOSS TO DIE AND DRY OVER 4-6 WEEKS; BRUSH OFF. DO NOT PRESSURE WASH (THE JET PENETRATES UNDER TILE EDGES AND CAN LIFT TILES AND FORCE WATER INTO THE SARKING). 4. MISSING OR FAILED SARKING (UNDERLAY): ORIGINAL VICTORIAN ROOFS WERE TYPICALLY BUILT WITHOUT A SARKING MEMBRANE (JUST BATTENS ON RAFTERS) — WIND-DRIVEN RAIN AND SNOW DIRECTLY ENTERS AROUND THE TILE EDGES AND THROUGH TILE CRACKS. FITTING A BREATHABLE SARKING MEMBRANE IS PART OF A FULL RE-ROOF BUT CANNOT BE RETROFITTED TO A STANDING TILE ROOF WITHOUT STRIPPING.

SINGLE TILE REPLACEMENT: BROKEN OR SLIPPED TILES CAN BE REPLACED INDIVIDUALLY WITHOUT LIFTING ADJACENT TILES IF ACCESS IS AVAILABLE: - LIFT THE TILES IN THE COURSE ABOVE THE DEFECTIVE TILE (USING A TILE LIFTER OR A FLAT PRYBAR CAREFULLY INSERTED UNDER THE NI EDGE — DO NOT CRACK ADJACENT TILES). - REMOVE THE DEFECTIVE TILE. - FIT REPLACEMENT TILE — NI ONTO BATTEN; CHECK CAMBER ORIENTATION (CURVE UP); LOWER THE COURSE ABOVE. - NAIL THE REPLACEMENT TILE IF IT IS IN A NAILING COURSE. SOURCING MATCHING TILES: RECLAIMED PLAIN CLAY TILES — FROM LOCAL SALVAGE YARDS (LASSCO, THORNHILL RECYCLED BRICK AND TILE, BUILDSTOCK) — MUST MATCH PROFILE AND COLOUR AS CLOSELY AS POSSIBLE. NEW TILES: MARLEY PLAIN TILE (HEATHLAND — CLOSEST TO ORIGINAL MACHINE-PRESSED), DREADNOUGHT CLAY PLAIN TILE, KEYMER CLAY PLAIN TILE.

EMERGENCY ROOF REPAIR — STORM DAMAGE: WHERE MULTIPLE TILES ARE LOST OR BROKEN IN A STORM, EMERGENCY MEASURES ARE NEEDED BEFORE A ROOFER CAN ATTEND FOR A FULL REPAIR: - TEMPORARY WATERPROOFING: LARGE GAUGE POLYTHENE SHEET (MINIMUM 1000 GAUGE — 250 MICRON) DRAPED OVER THE RIDGE AND TIED TO THE GUTTERS WITH ROPE (DO NOT USE BRICKS TO WEIGHT IT — HEAVY ITEMS SLIDING OFF A PITCHED ROOF ARE DANGEROUS). DO NOT ATTEMPT TO WORK ON A ROOF IN WIND ABOVE APPROXIMATELY 20 MPH. - ROOF REPAIR TAPE: FROM INSIDE THE LOFT, SELF-ADHESIVE ROOF REPAIR TAPE (EZY-FIX ROOF REPAIR TAPE, GEOCEL STORM SEAL) CAN BE APPLIED OVER SARKING FELT PUNCTURES FROM BELOW — A TEMPORARY INTERIOR PATCH. THIS DOES NOT REPLACE EXTERNAL TILE REPLACEMENT BUT STOPS ACTIVE DRIPPING WHILE THE EXTERNAL REPAIR IS ARRANGED. - EMERGENCY ROOFER CALL-OUT: MOST LONDON ROOFING CONTRACTORS CAN RESPOND WITHIN 24-48 HOURS FOR EMERGENCY STORM DAMAGE. SCAFFOLDING MAY BE REQUIRED FOR LARGER AREAS OF DAMAGE — NOT ALL REPAIRS CAN BE DONE FROM A ROOF LADDER.

RE-ROOF DECISION GUIDE: FULL RE-ROOFING IS GENERALLY JUSTIFIED WHEN: - MORE THAN 25-30% OF TILES ARE CRACKED, DELAMINATING, OR BROKEN - THE BATTENS ARE ROTTEN (CRUMBLING OR SOFT WHEN PROBED) - THE SARKING FELT IS ABSENT OR UNIVERSALLY FAILED (STIFF, BRITTLE, TEARING) - WIDESPREAD SLIPPAGE AFFECTS MULTIPLE COURSES - PREVIOUS REPAIRS HAVE USED INCOMPATIBLE MATERIALS (CEMENT POINTING OVER LIME MORTAR; WRONG TILE TYPES) - THE ROOF IS MORE THAN 50-60 YEARS OLD WITHOUT A MAJOR RENOVATION

COSTS (SUPPLY AND FIT, LONDON 2025-2026): SINGLE PLAIN TILE REPLACEMENT (RECLAIMED CLAY — SUPPLY AND FIT PER TILE): £50-150 (MAINLY SCAFFOLDING CALL-OUT) STRIP AND RE-ROOF WITH RECLAIMED CLAY PLAIN TILES (PER M²): £90-160/M² STRIP AND RE-ROOF WITH NEW CLAY PLAIN TILES (MARLEY, DREADNOUGHT — PER M²): £100-180/M² STRIP AND RE-ROOF WITH CONCRETE PLAIN TILE (NOT RECOMMENDED FOR CONSERVATION AREAS — PER M²): £60-100/M² BREATHABLE SARKING MEMBRANE AND RE-BATTEN (PART OF ANY FULL RE-ROOF): INCLUDED SCAFFOLDING (TYPICAL LONDON VICTORIAN TERRACE — PER WEEK): £1,500-3,000