Converting a House to Flats in London: Planning, Building Regulations, and HMO Rules

CONVERTING A HOUSE INTO TWO OR MORE SELF-CONTAINED FLATS IS A \"CHANGE OF USE\" UNDER PLANNING LAW AND REQUIRES PLANNING PERMISSION IN ALL CASES — THERE IS NO PERMITTED DEVELOPMENT RIGHT FOR HOUSE-TO-FLAT CONVERSION IN ENGLAND.

WHAT PLANNING PERMISSION COVERS: THE PLANNING APPLICATION FOR A HOUSE-TO-FLAT CONVERSION ADDRESSES: - THE PRINCIPLE OF CREATING SEPARATE DWELLINGS (CHANGE OF USE FROM CLASS C3 HOUSE TO CLASS C3 FLATS — CONFUSINGLY BOTH ARE C3, BUT THE CHANGE IN NUMBER OF UNITS REQUIRES PERMISSION) - EXTERNAL CHANGES (ADDITIONAL WINDOWS, DOORS, CYCLE STORAGE, BIN STORAGE, EXTERNAL STAIR ESCAPE — ALL REQUIRE PLANNING ASSESSMENT) - PARKING (LONDON PLAN POLICIES REQUIRE ASSESSMENT OF PARKING IMPACT) - AMENITY (THE LOCAL PLAN AND LONDON PLAN SET MINIMUM INTERNAL FLOOR AREA STANDARDS PER DWELLING — KNOWN AS THE LONDON HOUSING DESIGN GUIDE/NATIONALLY DESCRIBED SPACE STANDARDS)

NATIONALLY DESCRIBED SPACE STANDARDS (NDSS) — MINIMUM FLAT SIZES IN LONDON: SINCE 2016, MOST LONDON BOROUGHS REQUIRE NEW DWELLINGS (INCLUDING CONVERSIONS) TO MEET THE NDSS: - 1 BEDROOM (1-2 PERSON): MINIMUM 37M² (1-BED FLAT) - 1 BEDROOM (2 PERSON): MINIMUM 50M² - 2 BEDROOM (3 PERSON): MINIMUM 61M² - 2 BEDROOM (4 PERSON): MINIMUM 70M² A VICTORIAN TERRACE BEING CONVERTED INTO TWO FLATS MUST PRODUCE FLATS MEETING THESE MINIMUM SIZES. THIS LIMITS THE NUMBER OF UNITS ACHIEVABLE IN A TYPICAL VICTORIAN TERRACE (FLOOR AREA 85-130M² INCLUDING CELLAR/BACK ADDITION).

PLANNING APPLICATION PROCESS: HOUSEHOLDER PLANNING APPLICATION FEE (ENGLAND, 2024+): £528 FOR CHANGE OF USE. THE APPLICATION REQUIRES: - FLOOR PLANS (EXISTING AND PROPOSED — SHOWING ALL ROOMS, DIMENSIONS, AND UNIT LAYOUT) - DESIGN AND ACCESS STATEMENT - FIRE ESCAPE STRATEGY DIAGRAM (OFTEN REQUESTED BY PLANNERS AT PRE-APP OR APPLICATION STAGE) - ECOLOGY/BATS SURVEY (IF THE PROPERTY HAS POTENTIAL ROOST HABITAT — COMMON IN OLDER LONDON PROPERTIES)

PRE-APPLICATION ADVICE: STRONGLY RECOMMENDED BEFORE A HOUSE-TO-FLAT CONVERSION APPLICATION. THE BOROUGH WILL INDICATE WHETHER THE PROPOSED NUMBER OF UNITS IS ACCEPTABLE IN PRINCIPLE, WHETHER MINIMUM SIZES ARE MET, AND WHETHER EXTERNAL FIRE ESCAPE ROUTES WILL BE REQUIRED.

A HOUSE-TO-FLAT CONVERSION IS ONE OF THE MOST BUILDING-REGULATIONS-INTENSIVE PROJECTS IN RESIDENTIAL CONSTRUCTION. THE KEY PARTS ARE:

PART B (FIRE SAFETY): THE NEW FLAT CONFIGURATION CREATES SEPARATE FIRE COMPARTMENTS. BUILDING REGULATIONS REQUIRE: - FIRE COMPARTMENTATION BETWEEN FLATS (60-MINUTE FIRE SEPARATION — FD60S DOORS, 60-MINUTE FIRE-RATED CONSTRUCTION FOR FLOORS AND WALLS BETWEEN FLATS). - PROTECTED ESCAPE ROUTE FROM EACH FLAT DOOR TO FINAL EXIT (TYPICALLY THE HALL AND STAIR): MINIMUM 30-MINUTE FIRE RESISTANCE (FD30S LOBBY/HALL DOORS); SELF-CLOSING DEVICES (PERKO PC100 OR DORMA BHMA-GRADE CLOSERS); INTUMESCENT SEALS TO DOOR FRAMES (LORIENT LAS23 OR LEADERFLUSH HF23). - MAINS-WIRED INTERLINKED FIRE DETECTION: AICO EI3016 OPTICAL SMOKE DETECTORS IN HALLS, LANDINGS; AICO EI3014 HEAT DETECTOR IN KITCHEN OF EACH FLAT; ALL INTERLINKED (AICO EI414 RADIOLINK OR HARDWIRED). MINIMUM GRADE D CATEGORY LD2 (BS 5839-6:2019). - EMERGENCY LIGHTING IN COMMON AREAS (HALL, STAIR): STANDALONE EMERGENCY LUMINAIRES OR INTEGRATED MAINTAINED EMERGENCY LIGHTING.

PART E (SOUND INSULATION — MOST TECHNICALLY DEMANDING ELEMENT): THE FLOOR BETWEEN THE GROUND-FLOOR FLAT AND THE UPPER-FLOOR FLAT IS THE CRITICAL ACOUSTIC ELEMENT. PART E REQUIRES: - AIRBORNE SOUND INSULATION: MINIMUM DW 45 DW (MEASURED POST-COMPLETION — REQUIRES ACOUSTIC TESTING BY AN ACCREDITED ACOUSTIC ENGINEER). - IMPACT SOUND TRANSMISSION: MAXIMUM L\'NT,W 62 DB (MEASURED POST-COMPLETION). TO ACHIEVE THESE STANDARDS IN A VICTORIAN TERRACE WITH TIMBER JOIST FLOORS (220-250MM JOISTS): THE STANDARD APPROACH IS: 1. ADD INDEPENDENT CEILING (RESILIENT BAR CEILING — BRITISH GYPSUM OR KNAUF RESILIENT BAR AT 450MM CENTRES; 2 LAYERS 12.5MM SOUNDBLOC BOARD; ACOUSTIC PUTTY PADS ON BACK BOXES; ACOUSTIC MINERAL WOOL BATT ABOVE RESILIENT BARS): ACHIEVES APPROXIMATELY RW 47-52 DW. 2. ACOUSTIC FLOATING FLOOR ABOVE (DRY SCREED ON REGUPOL ACOUSTIC MAT 5MM, OR KNAUF INSULATED FLOATING FLOOR — 28MM FLOORING GRADE CHIPBOARD ON ACOUSTIC MATT): IMPROVES IMPACT ISOLATION. 3. FILL JOIST VOID WITH ACOUSTIC MINERAL WOOL (ROCKWOOL RW3 OR ACOUSTIC ROLL): IMPROVES AIRBORNE ATTENUATION. ACOUSTIC TEST ON COMPLETION IS REQUIRED BY BUILDING CONTROL.

PART M (ACCESSIBILITY): NEW FLATS CREATED BY CONVERSION MUST MEET PART M CATEGORY 1 (VISITABLE DWELLINGS) WHERE PRACTICABLE. THIS INCLUDES: LEVEL THRESHOLD AT ENTRANCE; MINIMUM DOOR WIDTHS (775MM CLEAR); TOILET AT ENTRANCE LEVEL (OR GROUND FLOOR WHERE APPLICABLE). IN A TWO-STOREY CONVERSION, THE GROUND FLOOR FLAT WILL TYPICALLY MEET M1 MORE EASILY — THE UPPER FLAT MAY BE DIFFICULT DUE TO STAIR ACCESS.

A HOUSE IN MULTIPLE OCCUPATION (HMO) IS DISTINCT FROM A HOUSE CONVERTED INTO SELF-CONTAINED FLATS — BUT THE DISTINCTION IS FREQUENTLY CONFUSED.

SELF-CONTAINED FLATS vs HMO: - SELF-CONTAINED FLAT: A UNIT WITH ITS OWN PRIVATE ENTRANCE, KITCHEN, BATHROOM, AND SLEEPING AREAS — NOT SHARED WITH OTHER TENANTS. A CONVERTED TERRACE WITH TWO SELF-CONTAINED FLATS IS NOT AN HMO. - HMO: A PROPERTY SHARED BY THREE OR MORE UNRELATED INDIVIDUALS WHO SHARE FACILITIES (KITCHEN, BATHROOM) AND FORM MORE THAN ONE HOUSEHOLD. AN HMO REQUIRES PLANNING PERMISSION (CHANGE OF USE TO C4 FOR 3-6 UNRELATED PERSONS) OR A LICENCE (FOR LARGE HMOs OF 5+ PERSONS SHARING — MANDATORY HMO LICENCE IN ENGLAND).

ADDITIONAL LICENSING / SELECTIVE LICENSING IN LONDON: MANY LONDON BOROUGHS OPERATE ADDITIONAL LICENSING SCHEMES (FOR SMALLER HMOs WITH 2-4 PERSONS SHARING, NOT COVERED BY MANDATORY LICENSING) AND SELECTIVE LICENSING SCHEMES (WHICH CAN REQUIRE ALL LANDLORDS IN A DESIGNATED AREA TO HOLD A LICENCE — INCLUDING FOR STANDARD SELF-CONTAINED FLATS). LANDLORDS MUST CHECK THE SPECIFIC BOROUGH LICENSING REQUIREMENTS.

FREEHOLDER AND LEASEHOLDER ISSUES: IF THE VICTORIAN TERRACE IS HELD UNDER A LEASE (RATHER THAN FREEHOLD), THE LEASE MUST BE CHECKED — SOME LEASES PROHIBIT SUB-DIVISION INTO FLATS. THE FREEHOLDER\'S CONSENT MAY BE REQUIRED. IF THE PROPERTY IS FREEHOLD, NEW LEASES SHOULD BE CREATED FOR EACH FLAT (LONG LEASES — 125-999 YEARS) BEFORE SALE OR MORTGAGE.

THE FOLLOWING COST RANGES APPLY TO A TWO-FLAT CONVERSION OF A LONDON VICTORIAN TERRACE (3-BEDROOM HOUSE TO TWO 1/2-BEDROOM SELF-CONTAINED FLATS):

PROFESSIONAL AND STATUTORY FEES: PRE-APPLICATION ADVICE: £200-600 (BOROUGH FEE) PLANNING APPLICATION: £528 (CHANGE OF USE FEE) PLANNING CONSULTANT/ARCHITECT (DRAWINGS + APPLICATION): £3,000-6,000 BUILDING CONTROL (APPROVED INSPECTORS): £1,200-2,500 ACOUSTIC ENGINEER (TESTING + REPORT): £600-1,200 STRUCTURAL ENGINEER (IF REQUIRED FOR FLOOR/STAIR ALTERATIONS): £800-1,500 PARTY WALL SURVEYOR (IF PARTY WALL ISSUES): £700-2,500

CONSTRUCTION COSTS: ACOUSTIC FLOOR/CEILING UPGRADE (25M² JOIST FLOOR): £4,000-8,000 FIRE DOORS + FRAMES + CLOSERS + INTUMESCENT SEALS (5-8 DOORS): £3,000-7,000 FIRE ALARM SYSTEM (AICO INTERLINKED, FULL PROPERTY): £800-1,800 EMERGENCY LIGHTING (COMMON AREAS): £500-1,000 SECOND KITCHEN (IF NEW FLAT NEEDS KITCHEN): £3,000-8,000 SECOND BATHROOM (IF NEW FLAT NEEDS BATHROOM): £4,000-10,000 EXTERNAL FIRE ESCAPE (IF REQUIRED — METAL STAIR): £2,000-6,000 ELECTRICAL (METERS, DISTRIBUTION, PART P CERTIFICATE): £2,000-5,000 PLUMBING (SEPARATE HOT AND COLD, HEATING CIRCUIT): £2,000-5,000 DECORATION AND FINISHES: £2,000-5,000 TOTAL CONSTRUCTION (EXCLUDING MAJOR STRUCTURAL WORK): £25,000-55,000

VALUE UPLIFT: A LONDON VICTORIAN TERRACE CONVERTED TO TWO SELF-CONTAINED FLATS TYPICALLY INCREASES THE TOTAL PROPERTY VALUE BY 20-40% OVER THE SINGLE-HOUSE VALUE — JUSTIFYING THE CONVERSION COST IN MOST INNER/MID LONDON MARKETS.