Porch Construction for London Victorian Terraces: Planning, Specification, and Costs

UNDER GPDO 2015 (THE GENERAL PERMITTED DEVELOPMENT ORDER 2015 — ENGLAND — SCHEDULE 2 PART 1 CLASS D — THE ERECTION OR CONSTRUCTION OF A PORCH OUTSIDE ANY EXTERNAL DOOR OF A DWELLING HOUSE), A PORCH CAN BE BUILT WITHOUT PLANNING PERMISSION PROVIDED ALL OF THE FOLLOWING CONDITIONS ARE MET.

CLASS D PERMITTED DEVELOPMENT CONDITIONS FOR A PORCH: (1) THE GROUND AREA COVERED BY THE PORCH (MEASURED EXTERNALLY — INCLUDING THE OUTER WALL THICKNESS) MUST NOT EXCEED 3M² — A SMALL PORCH CAN BE APPROXIMATELY 1.5M WIDE X 1.5M DEEP (EXTERNALLY) = 2.25M² — WITHIN THE 3M² LIMIT; (2) THE MAXIMUM HEIGHT OF THE PORCH MUST NOT EXCEED 3M ABOVE GROUND LEVEL (MEASURED FROM THE ORIGINAL GROUND LEVEL TO THE HIGHEST POINT OF THE PORCH — THE ROOF OR RIDGE); (3) THE PORCH MUST NOT BE CLOSER THAN 2M FROM THE BOUNDARY OF THE DWELLING WITH A HIGHWAY (I.E., IF THE FRONT GARDEN IS LESS THAN 2M DEEP FROM THE PAVEMENT TO THE FRONT DOOR, THE PORCH CANNOT PROTRUDE INTO THE REMAINING GARDEN SPACE WITHIN 2M OF THE HIGHWAY BOUNDARY — NOTE: IN MANY LONDON VICTORIAN TERRACES THE FRONT GARDEN IS LESS THAN 2M DEEP — THIS CONDITION CAN PREVENT PERMITTED DEVELOPMENT FOR A PROJECTING PORCH IN MANY INNER LONDON TERRACES WITH SHORT FRONT GARDENS); CONSERVATION AREA: IN A CONSERVATION AREA, CLASS D PERMITTED DEVELOPMENT FOR A PORCH IS TYPICALLY REMOVED — A PLANNING APPLICATION IS REQUIRED FOR ANY NEW PORCH STRUCTURE ON THE FRONT ELEVATION OF A PROPERTY IN A CONSERVATION AREA — AND MANY CONSERVATION OFFICERS WILL OBJECT TO A NEW PORCH IF THE ORIGINAL VICTORIAN TERRACE HAD NO PORCH. NOTE: SOME VICTORIAN TERRACES DID ORIGINALLY HAVE PORCHES — IN THESE CASES A LIKE-FOR-LIKE OR SYMPATHETIC REPLACEMENT PORCH MAY BE ACCEPTABLE. LISTED BUILDING: LISTED BUILDING CONSENT REQUIRED FOR ANY NEW PORCH ON A LISTED BUILDING — REGARDLESS OF SIZE.

THERE ARE SEVERAL TYPES OF PORCH STRUCTURE APPROPRIATE FOR A LONDON VICTORIAN TERRACE — RANGING FROM A SIMPLE OPEN CANOPY ABOVE THE FRONT DOOR TO A FULLY ENCLOSED PORCH WITH SIDE WALLS AND SECOND DOOR.

OPEN CANOPY (THE SIMPLEST AND LEAST PLANNING-SENSITIVE PORCH OPTION — A ROOF CANOPY STRUCTURE PROJECTING ABOVE THE FRONT DOOR — WITHOUT SIDE WALLS OR AN ENCLOSED SPACE): A LEAN-TO CANOPY (MONOPITCH ROOF SLOPE — A SINGLE PLANE ROOF SLOPING AWAY FROM THE FRONT WALL OF THE PROPERTY) IS THE MOST COMMON FORM OF OPEN CANOPY FOR A VICTORIAN TERRACE — TYPICALLY SUPPORTED ON SLENDER STEEL POSTS OR TIMBER POSTS AND FIXED TO THE FRONT WALL ABOVE THE DOOR; MATERIALS: POWDER-COATED STEEL FRAME WITH POLYCARBONATE OR GLASS ROOF PANEL (CLEAR, OPAL, OR TINTED) — OR A TIMBER FRAME WITH LEAD-COVERED TIMBER ROOF; OPEN CANOPY TYPICALLY: DOES NOT REQUIRE PLANNING PERMISSION (BELOW 3M² GROUND AREA, BELOW 3M HEIGHT, >2M FROM HIGHWAY BOUNDARY) AND DOES NOT REQUIRE BUILDING REGULATIONS APPROVAL (IT IS AN OPEN CANOPY — NOT AN ENCLOSED ROOM). LEAN-TO ENCLOSED PORCH (A SMALL LEAN-TO EXTENSION AT THE FRONT DOOR — WITH SIDE WALLS AND A SECONDARY INNER DOOR — CREATING AN ENCLOSED LOBBY SPACE): THE MOST FUNCTIONAL FORM OF PORCH — PROVIDES DRAUGHT EXCLUSION (THE AIRLOCK EFFECT OF A DOUBLE-DOOR LOBBY — THE OUTER DOOR IS OPENED AND CLOSED BEFORE THE INNER DOOR IS OPENED — PREVENTING COLD AIR DIRECTLY ENTERING THE HALLWAY — AN EFFECTIVE ENERGY-SAVING MEASURE IN A VICTORIAN TERRACE WITH A POORLY INSULATED HALLWAY); A LEAN-TO ENCLOSED PORCH WITHIN THE 3M² / 3M HEIGHT / 2M FROM HIGHWAY LIMITS IS PERMITTED DEVELOPMENT (SUBJECT TO CONSERVATION AREA CONSIDERATIONS ABOVE). FULLY ENCLOSED PORCH / LOBBY (LARGER ENCLOSED PORCH — EXCEEDING 3M² — REQUIRES PLANNING PERMISSION AND BUILDING REGULATIONS APPROVAL FOR THE CONSTRUCTION OF THE NEW ENCLOSURE): FOR A LARGER PORCH (>3M² GROUND AREA) — A HOUSEHOLDER PLANNING APPLICATION IS REQUIRED (FEE £258 ENGLAND 2024-2025) AND BUILDING REGULATIONS APPROVAL IS REQUIRED FOR THE STRUCTURAL WORKS (FOUNDATION, WALLS, ROOF) AND FOR THE THERMAL COMPLIANCE OF THE NEW ENCLOSED SPACE (PART L).

FOR A PERIOD-APPROPRIATE ENCLOSED PORCH ON A LONDON VICTORIAN TERRACE (WHERE PLANNING PERMISSION IS GRANTED OR WHERE PERMITTED DEVELOPMENT APPLIES), THE PREFERRED SPECIFICATION IS A BRICK-BUILT PORCH MATCHING THE EXISTING BRICK OF THE ORIGINAL FRONT ELEVATION — USING RECLAIMED YELLOW LONDON STOCK BRICK AND LIME MORTAR TO ENSURE COMPATIBILITY WITH THE EXISTING BUILDING FABRIC.

BRICK SPECIFICATION: RECLAIMED YELLOW LONDON STOCK BRICK (PREFERRED — MATCHING THE ORIGINAL YELLOW STOCK BRICK FRONT ELEVATION — SOURCES: LASSCO, RETROUVIUS, BRITANNIA, FRESHFIELD LANE NEW HANDMADE YELLOW STOCK — SEE GARDEN WALLS GUIDE). MORTAR: ST ASTIER NHL 3.5 1:2.5 WASHED SHARP SAND (LIME MORTAR — MATCHING THE ORIGINAL LIME MORTAR BEDDING OF THE EXISTING FRONT ELEVATION — NOT OPC SAND-CEMENT WHICH IS TOO HARD FOR YELLOW LONDON STOCK BRICK). FOUNDATION: CONCRETE STRIP FOUNDATION (MINIMUM 600MM WIDE X 300MM DEEP — REINFORCED C25 CONCRETE — THE PORCH FOUNDATION MUST BE DESIGNED BY A STRUCTURAL ENGINEER OR SPECIFIED PER PART A BUILDING REGULATIONS — DEPTH DEPENDING ON LONDON CLAY DEPTH AND TREE PROXIMITY — MINIMUM 1.0M FOR LONDON CLAY WHERE NO TREES WITHIN 5M — POSSIBLY DEEPER WHERE MATURE TREES IN FRONT GARDEN). ROOF: A LEAN-TO ROOF (MONOPITCH) IS THE MOST COMMON FORM FOR A COMPACT PORCH ON A VICTORIAN TERRACE — SPECIFICATION: ROUGH SAWN TIMBER FIRINGS AND RAFTERS (C16 STRUCTURAL TIMBER) — SARKING BOARD (12MM OSB/3 STRUCTURAL BOARD) — LEAD COVER SHEET (CODE 4 LEAD BS EN 12588:2006 — OVER THE ROOF DECK — WITH LEAD STEPPED AND COVER FLASHING TO THE FRONT WALL ABOVE — THE ROOF/WALL JUNCTION IS A CRITICAL WEATHERPROOFING DETAIL) — OR ALTERNATIVE: CLAY PLAIN TILE (MARLEY DOUBLETOP 265X165MM MACHINE-MADE CLAY PLAIN TILE — MATCHING THE ORIGINAL VICTORIAN TERRACE PLAIN TILE FRONT PITCH — TILE BATTENS AND ROOFING FELT MEMBRANE UNDER). EXTERNAL DOOR: THE OUTER PORCH DOOR (FRONT ENTRY TO THE PORCH LOBBY): COMPOSITE OR TIMBER EXTERNAL DOOR — VICTORIAN STYLE (4-PANEL OR 6-PANEL) TO MATCH THE PERIOD CHARACTER — GLAZING BARS IF APPROPRIATE — SECURE LOCK (BS 3621 BRITISH STANDARD KITEMARKED MULTIPOINT LOCK).

AN ENCLOSED PORCH THAT CREATES A NEW HABITABLE SPACE OR CHANGES THE THERMAL ENVELOPE OF THE DWELLING (EVEN IF UNHEATED) REQUIRES BUILDING REGULATIONS APPROVAL UNDER PART A (STRUCTURE), PART C (SITE PREPARATION AND MOISTURE RESISTANCE), PART L (CONSERVATION OF FUEL AND POWER), AND PART N (GLAZING) — WHERE THE PORCH EXCEEDS THE SMALL EXEMPT STRUCTURE SIZE.

EXEMPT FROM BUILDING REGULATIONS (SCHEDULE 2 OF THE BUILDING REGULATIONS 2010 — EXEMPT BUILDINGS AND WORK — CLASS VI): A PORCH ATTACHED TO AN EXISTING DWELLING IS EXEMPT FROM BUILDING REGULATIONS WHERE: (A) IT DOES NOT AFFECT THE STRUCTURAL STABILITY OF THE EXISTING DWELLING; (B) THE PORCH HAS AT LEAST ONE TRANSPARENT OR TRANSLUCENT WALL (GLAZED SIDE PANEL OR DOOR) AND AN OPAQUE ROOF; (C) THE EXISTING EXTERNAL DOOR BETWEEN THE EXISTING BUILDING AND THE NEW PORCH IS NOT REMOVED OR MADE REDUNDANT (I.E., THERE IS STILL AN EXTERNAL DOOR BETWEEN THE CONDITIONED SPACE OF THE DWELLING AND THE PORCH — THE PORCH IS NOT INCORPORATED INTO THE THERMAL ENVELOPE OF THE DWELLING — A PORCH THAT REPLACES THE EXTERNAL DOOR AND BECOMES PART OF THE HEATED HALLWAY IS NOT EXEMPT). IF THE PORCH IS EXEMPT UNDER SCHEDULE 2: NO BUILDING REGULATIONS APPROVAL IS REQUIRED — THE CONSTRUCTION CAN PROCEED WITHOUT FORMAL BC SUBMISSION. IF NOT EXEMPT (PORCH DOES NOT MEET ALL THREE CONDITIONS — OR EXCEEDS A STRUCTURAL FLOOR AREA BEYOND A BASIC CANOPY AND SIDE WALLS): BUILDING REGULATIONS APPROVAL IS REQUIRED — SUBMIT EITHER A FULL PLANS APPLICATION OR A BUILDING NOTICE TO THE LOCAL AUTHORITY BUILDING CONTROL (OR APPROVED INSPECTOR). PART L (THERMAL PERFORMANCE — FOR A NON-EXEMPT PORCH): THE NEW ENCLOSED STRUCTURE MUST MEET PART L BACKSTOP U-VALUES — EXTERNAL WALLS: 0.30 W/M²K; ROOF: 0.20 W/M²K; FLOOR: 0.25 W/M²K; WINDOWS AND DOORS: 1.4 W/M²K WHOLE-WINDOW U-VALUE (PART L 2021 BACKSTOP FOR REPLACEMENT WINDOWS IN EXISTING DWELLINGS) — IN PRACTICE, DOUBLE OR TRIPLE GLAZED COMPOSITE PORCH DOORS (U-VALUE 1.0-1.4 W/M²K WHOLE DOOR) MEET THIS MINIMUM.

PORCH CONSTRUCTION COSTS (LONDON 2025 — BUILDING CONTRACTOR — SUPPLY AND FIT — LABOUR AND MATERIALS — APPROXIMATE RANGE).

SIMPLE OPEN CANOPY (POWDER-COATED STEEL OR TIMBER FRAME — POLYCARBONATE OR GLASS ROOF PANEL — FIXED TO FRONT WALL — SUPPLY AND FIT): APPROXIMATELY £800-2,500 (DEPENDING ON SIZE, MATERIAL, AND PROFILE — SIMPLE LEAN-TO CANOPY 1.5M WIDE X 1.0M PROJECTION — SUPPLY AND FIT). SMALL ENCLOSED PORCH (BRICK BUILT — RECLAIMED YELLOW STOCK — NHL MORTAR — CONCRETE STRIP FOUNDATION — LEAN-TO LEAD ROOF — TIMBER GLAZED SIDE PANELS — COMPOSITE EXTERNAL DOOR — UP TO 3M² GROUND AREA — WITHIN PERMITTED DEVELOPMENT): APPROXIMATELY £4,000-9,000 (SUPPLY AND FIT — INCLUDING GROUNDWORK, BRICKWORK, ROOF, GLAZED PANELS, EXTERNAL DOOR — EXCLUDING PLANNING PERMISSION COSTS IF REQUIRED). LARGER ENCLOSED PORCH (>3M² GROUND AREA — REQUIRES PLANNING PERMISSION AND BUILDING REGULATIONS): APPROXIMATELY £8,000-18,000 (INCLUDING PLANNING APPLICATION, STRUCTURAL ENGINEER DRAWINGS, BUILDING REGULATIONS, GROUNDWORK, BRICKWORK, ROOF, GLAZING, DOOR — LARGER/MORE ELABORATE SPECIFICATION). PLANNING APPLICATION (HOUSEHOLDER APPLICATION — REQUIRED WHERE PORCH EXCEEDS PERMITTED DEVELOPMENT OR IS IN CONSERVATION AREA): £258 (ENGLAND PLANNING PORTAL 2024-2025 FEE). BUILDING REGULATIONS APPROVAL (FULL PLANS APPLICATION — WHERE PORCH IS NOT EXEMPT AND EXCEEDS BASIC SIZE): APPROXIMATELY £200-400 (LOCAL AUTHORITY FEE) + STRUCTURAL ENGINEER DRAWINGS APPROXIMATELY £400-800 (IF REQUIRED). NOTE: MOST SMALL PORCHES ON LONDON VICTORIAN TERRACES (BELOW 3M² — SINGLE LEAF COMPOSITE FRONT DOOR + SIDE PANEL — LEAN-TO ROOF) FALL WITHIN PERMITTED DEVELOPMENT AND THE BUILDING REGULATIONS EXEMPTION — AND CAN TYPICALLY BE COMPLETED FOR APPROXIMATELY £4,000-7,000 SUPPLY AND FIT WITHOUT PLANNING OR BUILDING REGULATIONS COSTS.