Roof Lights and Skylights for London Victorian Terraces: Types, Planning, and Costs

THERE ARE SEVERAL DISTINCT ROOF LIGHT CATEGORIES RELEVANT TO LONDON VICTORIAN TERRACES:

PITCHED ROOF VELUX-STYLE ROOF WINDOWS (IN-PLANE / FLUSH): ROOF WINDOWS INSTALLED FLUSH WITH THE EXISTING PITCHED ROOF SURFACE — THE GLASS IS SET INTO THE ROOF SLOPE WITH A FLASHING KIT THAT INTEGRATES WITH THE ROOF TILES: - VELUX PRODUCT RANGE (THE DOMINANT BRAND): GGL (CENTRE-PIVOT TIMBER FRAME), GGU (CENTRE-PIVOT POLYURETHANE FRAME), GPL (TOP-HUNG TIMBER), GPU (TOP-HUNG POLYURETHANE), FCM (FIXED — NON-OPENING — FOR MAXIMUM GLAZING AREA WHERE VENTILATION IS NOT REQUIRED) - ELECTRIC OPENING: VELUX INTEGRA (ELECTRIC MOTOR WITH RAIN SENSOR — CLOSES AUTOMATICALLY WHEN IT RAINS). ALSO AVAILABLE WITH SOLAR POWER (VELUX SOLAR INTEGRA). - SIZE: STANDARD SIZES FROM 550X780MM (SMALLEST — TYPICALLY USED FOR STAIRCASE LIGHT) TO 940X1600MM (LARGEST STANDARD VELUX) AND CUSTOM SIZES ABOVE THIS. - COMPETING BRANDS: FAKRO (POLISH — COMPETITIVE WITH VELUX ON PRICE; FTP-V, FT U RANGE); ROTO (GERMAN — ROTO WDT 700); KEYLITE (UK — INSTALLED AT SAME SPACING AS VELUX WITH UNIVERSAL FLASHING) - INSTALLATION: REQUIRES CUTTING THE RAFTERS AND INSTALLING A TIMBER TRIMMER FRAME (HEAD AND SILL TRIMMERS AT MIN. 38MM ABOVE RAFTERS); ROOF TILE CUTTING AND RELAYING AROUND THE FLASHING KIT; INTERNAL LINING (VELUX LSB INTERNAL REVEAL KIT OR CUSTOM PLASTERBOARD REVEALS)

CONSERVATION AREA ROOF WINDOWS: ON A LONDON CONSERVATION AREA PROPERTY, THE PERMITTED DEVELOPMENT RIGHT FOR ROOF WINDOWS HAS SPECIFIC ADDITIONAL CONSTRAINTS: - GPDO SCHEDULE 2, CLASS C.2: ROOF WINDOWS MUST NOT PROTRUDE MORE THAN 150MM FROM THE PLANE OF THE ROOF SLOPE — FLUSH VELUX AND EQUIVALENT PRODUCTS (SET BELOW THE RIDGE TILE LINE) USUALLY MEET THIS IF FITTED WITH THE STANDARD FLASHING (NOT THE "CONSERVATION" HIGHER-PROFILE FLASHING). - ON THE FRONT ROOF SLOPE IN A CONSERVATION AREA: PLANNING PERMISSION IS REQUIRED (EVEN IF THE STANDARD CLASS B PERMITTED DEVELOPMENT RIGHT WOULD OTHERWISE APPLY). MOST CONSERVATION OFFICERS WILL NOT APPROVE A ROOF WINDOW ON THE FRONT SLOPE OF A LISTED OR CONSERVATION AREA PROPERTY FACING THE STREET. - ON THE REAR ROOF SLOPE: USUALLY PERMITTED DEVELOPMENT — BUT MUST COMPLY WITH THE 150MM PROTRUSION LIMIT.

FLAT ROOF LIGHTS (FRAMELESS WALK-ON AND NON-WALK-ON): ROOFLIGHTS INSTALLED FLAT (0-15 DEGREES PITCH) IN A FLAT ROOF SURFACE — USED OVER REAR EXTENSIONS, GARAGES, AND OUTBUILDINGS: - FRAMELESS ROOFLIGHTS (THE "PITCHLESS" CATEGORY): DESIGNED FOR TRUE FLAT OR NEAR-FLAT ROOFS. MUST BE SELF-DRAINING (MINIMUM INTERNAL DRAINAGE CHANNELS AT PERIMETER). PRODUCTS: VELUX MODULAR SKYLIGHTS (VMS); ROOF MAKER FRAMELESS ROOFLIGHT (THE UK\'S LEADING INDEPENDENT FLAT ROOFLIGHT BRAND — AVAILABLE IN STANDARD AND BESPOKE SIZES); MARDOME (POLYCARBONATE DOME — LOWER-COST OPTION); ATLAS CONSERVATION ROOFLIGHT. - GLASS SPEC FOR FLAT ROOFLIGHTS: MUST BE LAMINATED GLASS ON THE INNER PANE (SAFETY — IF THE GLASS BREAKS, THE INNER LAMINATE HOLDS THE SHARDS AGAINST THE PERSON BELOW). DOUBLE-GLAZED (16MM ARGON GAS CAVITY) OR TRIPLE-GLAZED (ROOF MAKER HIGH PERFORMANCE). U-VALUE FOR BUILDING REGULATIONS PART L: ≤ 1.6 W/M²K FOR A NEW FLAT ROOFLIGHT (2021 PART L REQUIREMENTS). - LANTERNS (PITCHED GLASS PYRAMID OR RIDGE FORM): A LANTERN IS A THREE-DIMENSIONAL GLAZED STRUCTURE SITTING ON A KERB UPSTAND ABOVE THE FLAT ROOF SURFACE — A CENTRAL SPINE/RIDGE WITH GLAZED RAFTERS ON EACH SIDE. POPULAR IN KITCHEN EXTENSIONS.

STRUCTURAL REQUIREMENTS: ALL ROOF LIGHT INSTALLATIONS IN A PITCHED ROOF REQUIRE TIMBER TRIMMER FRAMING AROUND THE OPENING (HEADERS AND SILL TRIMMERS BETWEEN THE ADJACENT RAFTERS TO CARRY THE RAFTER LOADS AROUND THE OPENING). FOR LARGER OPENINGS (OVER TWO RAFTER BAYS — I.E., THREE OR MORE RAFTERS CUT), A STRUCTURAL ENGINEER SHOULD CONFIRM THE TRIMMER BEAM SIZE.

ROOF LIGHT AND SKYLIGHT COSTS (SUPPLY, LONDON 2025-2026): VELUX GGL CENTRE-PIVOT TIMBER ROOF WINDOW (STANDARD SIZE 780X980MM): £200-350 (SUPPLY ONLY) VELUX INTEGRA SOLAR ELECTRIC ROOF WINDOW (780X980MM): £650-900 (SUPPLY ONLY) FAKRO FTP-V ROOF WINDOW (EQUIVALENT SIZE): £150-250 (SUPPLY ONLY — COMPETITIVE WITH VELUX) VELUX STANDARD FLASHING KIT (COMPATIBLE ROOF TILES): £70-120 (SUPPLY ONLY) INSTALLATION OF ONE VELUX-STYLE ROOF WINDOW (LABOUR — OPEN RAFTER, FLASH, INTERNAL REVEAL): £400-700 FLAT FRAMELESS ROOFLIGHT (ROOF MAKER STANDARD — 1000X1000MM, DOUBLE-GLAZED): £900-1,500 (SUPPLY ONLY) FLAT ROOFLIGHT INSTALLATION (LABOUR — INCLUDING UPSTAND FORMING AND WATERPROOFING INTEGRATION): £500-900 GLASS LANTERN (RIDGE LANTERN — 1500X2000MM, ALUMINIUM FRAME, SELF-CLEANING GLASS): £2,500-6,000 (SUPPLY ONLY) GLASS LANTERN INSTALLATION (LABOUR — INCLUDING STRUCTURAL UPSTAND AND WATERPROOFING): £800-1,500

THERMAL PERFORMANCE AND BUILDING REGULATIONS: - EXISTING DWELLINGS (LIKE-FOR-LIKE REPLACEMENT): MINIMUM U-VALUE 1.8 W/M²K FOR A REPLACEMENT ROOF WINDOW UNDER PART L OF THE BUILDING REGULATIONS. - NEW EXTENSIONS: MINIMUM U-VALUE 1.6 W/M²K FOR ROOFLIGHTS (PART L1A 2021 — NEW DWELLINGS AND EXTENSIONS). - VELUX STANDARD DOUBLE GLAZING (ARGON-FILLED): U-VALUE TYPICALLY 1.2-1.4 W/M²K — COMFORTABLY MEETS PART L. - CENTRE-OF-GLASS G-VALUE: GLAZING SOLAR GAIN THROUGH ROOFLIGHTS IS SIGNIFICANT (ROOFLIGHTS FACE THE SKY DIRECTLY). INTERNAL BLINDS (VELUX MK04 BLACKOUT BLIND — FITTING CODE 4574 FOR FLAT ROOF) OR EXTERNAL AWNING BLINDS CONTROL SOLAR GAIN IN SUMMER. - CONDENSATION RISK: ROOFLIGHTS IN BATHROOMS AND KITCHENS NEED ADEQUATE VENTILATION BELOW THEM TO PREVENT CONDENSATION ON THE INNER GLASS SURFACE. VELUX ELECTRIC OPENING WINDOWS WITH RAIN SENSOR (INTEGRA) IMPROVE VENTILATION AND REDUCE CONDENSATION RISK.