Skylights for London Victorian Terraces: Fixed vs Opening, Dormer, and Walk-On Options

FIXED SKYLIGHTS (ROOFLIGHTS — DAYLIGHT ONLY): A FIXED SKYLIGHT IS PERMANENTLY CLOSED — IT ADMITS DAYLIGHT AND SOLAR HEAT BUT PROVIDES NO VENTILATION AND NO EMERGENCY ESCAPE ROUTE. APPROPRIATE APPLICATIONS IN A LONDON VICTORIAN TERRACE: - HALLWAYS AND LANDINGS (WHERE VENTILATION IS PROVIDED BY OTHER MEANS — EXISTING SASH WINDOWS, MECHANICAL EXTRACT) - REAR FLAT ROOF EXTENSIONS WHERE VENTILATION IS PROVIDED BY ADJACENT DOORS OR WINDOWS - BATHROOM SUN TUNNEL DIFFUSERS (FIXED — VENTILATION VIA MEV OR DMEV EXTRACT FAN) - OVER STAIRS OR OPEN-PLAN AREAS WHERE DAYLIGHT PENETRATION IS THE PRIORITY AND VENTILATION IS FROM OTHER SOURCES

FIXED SKYLIGHTS FOR FLAT ROOFS ARE AVAILABLE AS: - UPSTAND-MOUNTED UNITS (ON A RAISED KERB — MOST COMMON FLAT ROOF OPTION) - FLUSH-MOUNTED WALK-ON UNITS (FRAMELESS OR MINIMAL FRAME — FOR ACCESSIBLE ROOF TERRACES) - STRUCTURAL GLASS FLOORS (WALK-ON GLASS, FIRE-RESISTANT WHERE ABOVE ESCAPE ROUTES)

OPENING SKYLIGHTS (SKYLIGHT WINDOWS — DAYLIGHT AND VENTILATION): AN OPENING SKYLIGHT PROVIDES DAYLIGHT AND VENTILATION AND — IF OF SUFFICIENT CLEAR OPENING DIMENSIONS — CAN CONSTITUTE A HABITABLE ROOM EMERGENCY ESCAPE ROUTE UNDER PART B OF THE BUILDING REGULATIONS. APPROPRIATE APPLICATIONS IN A LONDON VICTORIAN TERRACE LOFT CONVERSION: - ALL HABITABLE ROOMS IN A LOFT CONVERSION (BUILDING REGS REQUIRE AT LEAST ONE OPENING ROOFLIGHT SATISFYING PART F VENTILATION REQUIREMENTS) - LOFT BEDROOM FIRE ESCAPE ROUTE (PART B: MINIMUM 0.33M² CLEAR OPENING, MIN 450×450MM, MAX SILL 1.1M FROM FLOOR) - KITCHEN AND BATHROOM EXTENSIONS WITH A FLAT ROOF WHERE OPENING SKYLIGHTS PROVIDE THE ONLY VENTILATION

OPENING SKYLIGHT TYPES: - CENTRE-PIVOT OPENING (VELUX GGL/GGU — THE UK MARKET STANDARD): THE MOST COST-EFFECTIVE OPENING OPTION FOR PITCHED ROOFS. SUITABLE FOR PITCHED ROOFS BETWEEN 15° AND 90°. - TOP-HUNG OPENING (VELUX GHL/GHU): HINGED AT THE TOP — UNOBSTRUCTED VIEW, BETTER UPPER-ZONE DAYLIGHT DISTRIBUTION. REQUIRES MORE HEADROOM. - ELECTRICALLY OPERATED OPENING SKYLIGHTS (VELUX INTEGRA SOLAR OR ELECTRIC): SOLAR-POWERED OR MAINS-WIRED, REMOTE CONTROL OR SMARTPHONE OPERATION, RAIN SENSOR AVAILABLE. RECOMMENDED FOR HARD-TO-REACH SKYLIGHTS IN LOFT CONVERSIONS. - FLAT ROOF OPENING SKYLIGHTS (E.G., VELUX CFP, FAKRO DMG, ARMSTRONG GLASS ROOF LIGHTS WITH CASEMENT OPENING): OPENING UNITS FOR FLAT ROOFS — TYPICALLY HINGED AT ONE SIDE; SUITABLE WHERE BOTH DAYLIGHT AND VENTILATION ARE REQUIRED FROM A FLAT ROOF.

PART F (VENTILATION) REQUIREMENTS FOR SKYLIGHTS IN HABITABLE ROOMS: UNDER BUILDING REGULATIONS PART F, HABITABLE ROOMS MUST HAVE RAPID VENTILATION (OPENABLE WINDOW OR SKYLIGHT) WITH AN AREA AT LEAST 1/20TH OF THE FLOOR AREA. FOR A 15M² LOFT BEDROOM, THE OPENING AREA MUST BE AT LEAST 0.75M² — A VELUX FK06 (66×118CM) CENTRE-PIVOT PROVIDES A CLEAR OPENING OF APPROXIMATELY 0.5M² WHEN FULLY OPEN; AN FK08 (66×140CM) PROVIDES APPROXIMATELY 0.6M². IN PRACTICE, TWO FK04 OR LARGER UNITS ARE OFTEN SPECIFIED TO SATISFY PART F VENTILATION IN A LOFT CONVERSION BEDROOM.

DORMER-STYLE SKYLIGHTS: A DORMER SKYLIGHT IS A COMBINATION OF A VERTICAL-FACE WINDOW AND A PROJECTING DORMER STRUCTURE — THE WINDOW SITS IN THE VERTICAL FACE OF A DORMER BOX THAT PROJECTS FROM THE ROOF SLOPE. DORMER SKYLIGHTS PROVIDE MORE USABLE HEADROOM THAN A SLOPED VELUX-TYPE UNIT AND ARE THE PREFERRED SPECIFICATION FOR A LOFT CONVERSION BEDROOM: - CONSTRUCTION: A TIMBER OR STEEL DORMER BOX PROJECTS FROM THE MAIN ROOF SLOPE; THE DORMER CHEEKS (SIDE WALLS) ARE TYPICALLY LEAD-CLAD OR ZINC-CLAD; THE DORMER ROOF IS A FLAT LEAD OR ZINC UPSTAND ROOF; THE DORMER FACE IS A CONVENTIONAL VERTICAL OPENING CASEMENT OR SASH WINDOW. - PLANNING: A REAR DORMER (FACING THE GARDEN — NOT THE HIGHWAY) ON A LONDON VICTORIAN TERRACE IS PERMITTED DEVELOPMENT (NO PLANNING REQUIRED) IF: IT DOES NOT EXTEND BEYOND THE PLANE OF THE EXISTING ROOF SLOPE FACING A HIGHWAY; THE DORMER VOLUME DOES NOT EXCEED 40M³ (TERRACED HOUSE); NO PART OF THE DORMER PROTRUDES ABOVE THE HIGHEST PART OF THE EXISTING ROOF; NO BALCONY OR VERANDA IS INCLUDED; THE DORMER IS SET BACK A MINIMUM OF 200MM FROM EACH EAVE.

WALK-ON GLASS SKYLIGHTS: WALK-ON GLASS SKYLIGHTS ARE SET INTO THE FLOOR OF AN UPPER LEVEL OR ROOF TERRACE TO ALLOW DAYLIGHT TO PASS DOWN TO THE SPACE BELOW. TYPICAL APPLICATIONS IN A LONDON VICTORIAN EXTENSION: - OVER A REAR EXTENSION: GLASS FLOOR PANELS IN THE UPPER FLOOR ALLOW DAYLIGHT TO PASS FROM A VELUX OR ROOFLIGHT ABOVE DOWN INTO THE GROUND-FLOOR EXTENSION BELOW — PARTICULARLY USEFUL FOR DEEP PLAN EXTENSIONS WHERE THE GROUND FLOOR DOES NOT EXTEND BACK AS FAR AS THE ROOFLIGHT. - ROOF TERRACE WALK-ON LIGHT: WHERE THE EXTENSION ROOF IS USED AS AN ACCESSIBLE TERRACE, A WALK-ON ROOFLIGHT SET INTO THE TERRACE FLOOR ILLUMINATES THE ROOM BELOW. MUST BE WALK-ON RATED (PAS 24 / BS EN 1873 — MINIMUM 0.3 KN/M² IMPOSED LOAD; ANTI-SLIP TOP SURFACE, TYPICALLY SANDBLASTED OR ACID-ETCHED; STRUCTURAL GLASS THICKNESS TYPICALLY 33.1+16MM+33.1 TRIPLE LAMINATE).

PLANNING SUMMARY FOR SKYLIGHTS IN LONDON VICTORIAN TERRACES: - REAR PITCHED ROOF (VELUX-TYPE OPENING OR FIXED ROOFLIGHT): PERMITTED DEVELOPMENT — NO PLANNING REQUIRED IN MOST CASES (MAX PROTRUSION 150MM ABOVE SLOPE; NOT HIGHEST PART OF EXISTING ROOF; NOT FORWARD OF PRINCIPAL ELEVATION). - REAR DORMER: PERMITTED DEVELOPMENT IF WITHIN THE 40M³ VOLUME LIMIT, SET BACK 200MM FROM EAVES, NOT ABOVE HIGHEST ROOF POINT, AND NOT ON A LISTED BUILDING. - FLAT ROOF SKYLIGHTS/ROOFLIGHTS: USUALLY PERMITTED DEVELOPMENT IF NOT VISIBLE FROM A HIGHWAY — BUT CONFIRM WITH THE LOCAL PLANNING AUTHORITY. - CONSERVATION AREA AND LISTED BUILDING: Conservation ROOFLIGHTS (FLUSH-FIT) ARE PREFERRED FOR ANY SKYLIGHT VISIBLE FROM A HIGHWAY; LISTED BUILDINGS REQUIRE LISTED BUILDING CONSENT FOR ANY ALTERATION. - ARTICLE 4 DIRECTION: SOME LONDON BOROUGHS (E.G., ISLINGTON, CAMDEN, WANDSWORTH) HAVE ARTICLE 4 DIRECTIONS REMOVING PERMITTED DEVELOPMENT RIGHTS FOR ROOF ALTERATIONS IN CONSERVATION AREAS — CHECK WITH THE LPA BEFORE PROCEEDING.

COSTS (SUPPLY AND FIT, LONDON 2025-2026): FIXED FLAT ROOF SKYLIGHT (DOUBLE GLAZED UPSTAND, 1200×1200, SUPPLY AND FIT): £1,500-3,000 OPENING FLAT ROOF SKYLIGHT (1200×1200, SUPPLY AND FIT): £2,000-4,500 WALK-ON GLASS ROOFLIGHT (TRIPLE LAMINATE, 1200×1200, SUPPLY AND FIT): £3,000-8,000 REAR DORMER (FULL DORMER CONVERSION — STRUCTURAL, LEAD CHEEKS, WINDOW): £15,000-35,000 SUN TUNNEL (SMALL DIAMETER — DAYLIGHT ONLY): £500-1,200