Rear Wall Glazing in London Victorian Terraces: Bifold, Sliding, and Fixed Glass

THE CHOICE OF REAR WALL GLAZING SYSTEM DETERMINES THE VISUAL CHARACTER OF THE REAR ELEVATION, THE FUNCTIONAL INDOOR-OUTDOOR EXPERIENCE, AND THE STRUCTURAL IMPACT ON THE EXISTING REAR WALL. THE THREE MAIN SYSTEMS ARE:

BIFOLD DOORS: BIFOLD DOORS FOLD BACK IN CONCERTINA FASHION — EACH PANEL IS HINGED TO THE NEXT, AND THE WHOLE STACK FOLDS TO ONE OR BOTH ENDS OF THE OPENING, CREATING A FULL-WIDTH OPEN APERTURE. ADVANTAGES: MAXIMUM OPEN-UP (VIRTUALLY THE FULL OPENING BECOMES A DOORWAY WHEN FULLY OPEN); FLEXIBLE PANEL CONFIGURATION (2-3-4-6 PANELS PER SIDE); WELL-SUITED TO OPENINGS 2.4-6.0M WIDE. DISADVANTAGES: COMPLEX HARDWARE (MULTIPLE HINGES, TOP TRACK, BOTTOM THRESHOLD WITH SLIGHT TRIP HAZARD); PANELS REQUIRE SWING SPACE INSIDE OR OUTSIDE WHEN OPENING; STRUCTURAL BEAM ABOVE IS CRITICAL (ALL LOADS TRANSFERRED TO THE JAMBS AT EACH END WHEN OPEN). RECOMMENDED SYSTEMS: ORIGIN OB-49 (THERMALLY BROKEN ALUMINIUM, 107MM OUTER FRAME, TRIPLE GLAZED PILKINGTON OPTITHERM S3 PLUS 0.9 W/M²K); ALUK 58BF (58MM SIGHTLINE, EXCELLENT VALUE THERMALLY BROKEN ALU); SCHUCO ASS 70.HI (LIFT-AND-SLIDE — TECHNICALLY A SLIDE NOT BIFOLD, BUT VERY HIGH PERFORMANCE); SMART VISOGLIDE PLUS (BUDGET-TIER ALU).

SLIDING DOORS (LIFT-AND-SLIDE OR INLINE SLIDE): PANELS SLIDE ALONG A TRACK — ONE OR MORE PANELS SLIDE BEHIND EACH OTHER OR INTO A POCKET. THE OPENING IS PARTIAL (ONE PANEL ALWAYS COVERS PART OF THE APERTURE EVEN WHEN FULLY OPEN) UNLESS THE SYSTEM HAS A POCKET (WALL OR COLUMN) TO SLIDE PANELS INTO. ADVANTAGES: LOWER FRAME THRESHOLD (BETTER LEVEL ACCESS — BS 8300 COMPLIANT FLAT THRESHOLD OPTIONS); LARGER UNINTERRUPTED GLASS PANES WHEN CLOSED (CLEANER VIEW, BETTER THERMAL PERFORMANCE); LESS HARDWARE VISIBLE IN CLOSED STATE (CLEANER AESTHETIC); SMOOTHER OPERATION ON LARGE PANELS (LIFT-AND-SLIDE MECHANISM). DISADVANTAGES: SMALLER CLEAR OPENING THAN BIFOLDS (TYPICALLY 50% OF APERTURE OPENABLE AT ONE TIME, UNLESS POCKET SYSTEM); POCKET SYSTEMS REQUIRE MORE STRUCTURAL WORK. RECOMMENDED SYSTEMS: SCHUCO ASS 70.HI LIFT+SLIDE (PREMIUM — 70MM FRAME, TRIPLE-GLAZED, THERMAL BREAK); IQ GLASS SLIMLINE SLIDING; SUNPARADISE ISLAND SLIDING DOOR (LARGE FORMAT — UP TO 6M PANEL WIDTH).

FIXED GLAZING (FRAMELESS OR MINIMAL-FRAME GLASS SCREEN): A FIXED GLASS SCREEN — WITH ONLY MINIMAL FRAMING — IN THE REAR WALL OF AN EXTENSION, SOMETIMES COMBINED WITH OPENING ELEMENTS (ROOFLIGHTS ABOVE, SINGLE DOOR TO SIDE): ADVANTAGES: MAXIMUM GLASS AREA FOR THE OPENING; MINIMAL SIGHTLINES (ESPECIALLY WITH STRUCTURAL GLASS BOLTED FIXINGS — IQ GLASS, GLASSOLUTIONS); UNINTERRUPTED VIEW; BEST THERMAL PERFORMANCE IN CLOSED STATE (NO OPERATING HARDWARE THERMAL BRIDGES). DISADVANTAGES: NO VENTILATION (MUST BE COMBINED WITH OPENING ELEMENTS); CLEANEST AESTHETICALLY BUT LEAST FLEXIBLE FOR INDOOR-OUTDOOR LIVING.

ROOFLIGHTS AS PART OF THE REAR GLAZING SYSTEM: ROOFLIGHTS (FLAT ROOF WINDOWS) ON THE ROOF OF A REAR EXTENSION ARE OFTEN COMBINED WITH REAR WALL GLAZING TO CREATE A FULLY LIGHT-FLOODED KITCHEN-DINING SPACE: RECOMMENDED: VELUX MODULAR SKYLIGHTS (CUSTOM SIZE, DOUBLE GLAZED, IP65 INTEGRATED BLIND); FAKRO FTT U8 TRIPLE GLAZED FLAT ROOF WINDOW; IQ GLASS BESPOKE WALK-ON ROOFLIGHT (WHERE TERRACE IS ABOVE).

REPLACING THE REAR WALL OF A LONDON VICTORIAN TERRACE WITH GLAZING IS A STRUCTURAL ALTERATION — THE REAR WALL IS LOAD-BEARING (IT CARRIES THE FIRST-FLOOR REAR WALL AND OFTEN THE REAR SECTION OF THE ROOF). STRUCTURAL WORK IS ALWAYS REQUIRED:

STRUCTURAL BEAM ABOVE THE OPENING: A STEEL BEAM (UNIVERSAL BEAM — UB SECTION) IS INSTALLED ABOVE THE GLAZING OPENING TO CARRY THE LOADS PREVIOUSLY CARRIED BY THE REMOVED WALL SECTION: - TYPICAL OPENING 3.0M WIDE: UB 203X133X25 (S275 STEEL) — VERIFY WITH STRUCTURAL ENGINEER - TYPICAL OPENING 4.0M WIDE: UB 254X146X31 OR UB 305X127X37 — VERIFY WITH STRUCTURAL ENGINEER - OPENING 5.0M OR WIDER: UB 305X165X40 OR ABOVE; OR DOUBLE UB WITH SPREADER PLATES — STRUCTURAL ENGINEER SPECIFICATION MANDATORY

PADSTONES: AT EACH END OF THE BEAM, A PADSTONE (ENGINEERING BRICK OR CONCRETE PADSTONE — MINIMUM 215X215X100MM) DISTRIBUTES THE CONCENTRATED POINT LOAD FROM THE BEAM END INTO THE MASONRY ON EITHER SIDE OF THE OPENING. PADSTONE SIZE IS SPECIFIED BY THE STRUCTURAL ENGINEER.

TEMPORARY SUPPORT DURING WORKS: THE FIRST FLOOR AND ROOF LOADS MUST BE TEMPORARILY SUPPORTED WHILE THE REAR WALL IS OPENED UP: - ACROW PROPS (GROUNDFORCE SHORCO FRAME SYSTEM) INSTALLED BELOW THE FIRST-FLOOR JOISTS AT 600MM CENTRES, ON SPREADER BOARDS ON THE GROUND FLOOR BELOW - TEMPORARY SUPPORT MUST BE IN PLACE BEFORE ANY WALL IS REMOVED — REMOVAL BEFORE PROPPING IS A STRUCTURAL SAFETY RISK - ACROW PROPS ON UPPER FLOOR DURING INSTALLATION: NOT ALWAYS NECESSARY IF THE FIRST-FLOOR JOISTS SPAN PERPENDICULAR TO THE REAR WALL (FRONT-TO-BACK DIRECTION) — VERIFY WITH STRUCTURAL ENGINEER

BUILDING REGULATIONS: ANY REMOVAL OF STRUCTURAL MASONRY REQUIRES BUILDING REGULATIONS APPROVAL: 1. FULL PLANS APPLICATION (RECOMMENDED — APPROVED DRAWINGS BEFORE WORK STARTS) 2. STRUCTURAL ENGINEER\'S SPECIFICATION FOR BEAM, PADSTONES, AND TEMPORARY SUPPORT 3. BUILDING CONTROL INSPECTIONS: COMMENCEMENT; STEELWORK IN POSITION (BEFORE MAKING GOOD); PRACTICAL COMPLETION 4. COMPLETION CERTIFICATE FROM BUILDING CONTROL — ESSENTIAL FOR FUTURE SALE

PARTY WALL NOTICE (SECTION 2): IF THE REAR WALL IS A PARTY WALL (SHARED WITH A NEIGHBOURING PROPERTY — LESS COMMON AT THE REAR BUT POSSIBLE IN SOME TERRACE CONFIGURATIONS) OR IF THE BEAM BEARS INTO A PARTY WALL AT EITHER END: PARTY WALL ACT 1996 SECTION 2 NOTICE IS REQUIRED — SERVE ON ADJOINING OWNERS AT LEAST 2 MONTHS BEFORE WORKS.

PLANNING CONSIDERATIONS FOR REAR WALL GLAZING: WHERE THE REAR WALL GLAZING IS PART OF A REAR EXTENSION (MOST COMMON SCENARIO IN LONDON VICTORIAN TERRACES): - SINGLE-STOREY REAR EXTENSION WITH GLAZED REAR WALL: TYPICALLY PERMITTED DEVELOPMENT (WITHIN THE GPDO 2015 LIMITS — 3M DEPTH FOR TERRACED HOUSE UNDER PD; 6M UNDER PRIOR APPROVAL). PLANNING PERMISSION NOT REQUIRED IF WITHIN PD LIMITS. - GLAZING IN THE ORIGINAL REAR WALL (NO EXTENSION): ALSO PERMITTED DEVELOPMENT UNDER CLASS A (ENLARGEMENT OR IMPROVEMENT OF A DWELLINGHOUSE — ENLARGING A REAR OPENING). HOWEVER, IN A CONSERVATION AREA OR ARTICLE 4 DIRECTION AREA, WORKS TO THE REAR MAY STILL REQUIRE PLANNING PERMISSION — CHECK WITH LOCAL AUTHORITY.

THERMAL PERFORMANCE REQUIREMENTS (PART L): THE GLAZING MUST MEET BUILDING REGULATIONS PART L (CONSERVATION OF FUEL AND POWER) THERMAL PERFORMANCE REQUIREMENTS: - WINDOWS AND DOORS: MAXIMUM U-VALUE 1.4 W/M²K FOR REPLACEMENT WINDOWS/DOORS IN AN EXISTING DWELLING (2022 APPROVED DOCUMENT L1B) - FOR NEW EXTENSION GLAZING: AS PART OF A NEW EXTENSION, THE WHOLE EXTENSION MUST COMPLY WITH PART L — TYPICALLY U-VALUE ≤ 1.4 W/M²K FOR GLAZED ELEMENTS - TRIPLE GLAZED BIFOLDS (ORIGIN OB-49, SCHUCO ASS 70.HI): ACHIEVE U-VALUES OF 0.8-1.0 W/M²K (BETTER THAN REQUIRED) - DOUBLE GLAZED BIFOLDS (STANDARD SPEC): ACHIEVE U-VALUES OF 1.2-1.4 W/M²K (COMPLIANT BUT NOT PREMIUM)

SPECIFICATION SUMMARY FOR A TYPICAL LONDON TERRACE REAR GLAZING PROJECT: OPENING WIDTH: 3.5M (TYPICAL VICTORIAN TERRACE REAR ROOM WIDTH) SYSTEM: ORIGIN OB-49 ALUMINIUM BIFOLD (4 PANELS — 2 LEFT 2 RIGHT), TRIPLE GLAZED, ANTHRACITE GREY RAL 7016 STRUCTURAL BEAM: UB 254X146X31 S275 WITH 215X215X100MM ENGINEERING BRICK PADSTONES THRESHOLD: LOW-THRESHOLD ALUMINIUM SILL (ORIGIN FT-EXT — 18MM TRIP REDUCTION) ROOFLIGHT (IF FLAT ROOF EXTENSION): VELUX MODULAR SKYLIGHTS 1,200X1,200MM DOUBLE GLAZED

COSTS FOR REAR WALL GLAZING IN A LONDON VICTORIAN TERRACE (SUPPLY AND FIT, 2025-2026): STRUCTURAL BEAM AND PADSTONES (SUPPLY AND INSTALL, INCL. TEMPORARY SUPPORT): £2,500-4,500 BIFOLD DOORS — MID-RANGE ALU DOUBLE GLAZED (3.5M WIDE, 4 PANELS): £4,500-7,000 BIFOLD DOORS — PREMIUM ALU TRIPLE GLAZED ORIGIN/SCHUCO (3.5M WIDE): £8,000-14,000 SLIDING DOORS — LIFT-AND-SLIDE SCHUCO ASS 70.HI (3.5M WIDE): £9,000-16,000 FIXED GLAZING (FRAMELESS/MINIMAL FRAME, 3.5M WIDE): £6,000-12,000 ROOFLIGHT (VELUX MODULAR 1,200X1,200, SUPPLY AND FIT): £1,500-2,500 BUILDING CONTROL FULL PLANS APPLICATION FEE: £200-400