Rear Extensions in West Hampstead NW6

West Hampstead's Victorian and Edwardian properties offer wonderful character but often lack the open-plan living space modern families desire. Rear extensions provide an ideal solution, adding valuable square footage while creating bright, contemporary living areas that connect seamlessly with your garden. Whether you're looking to extend into your side return, add a single-storey rear extension, or create a dramatic two-storey addition, understanding the process, costs, and planning requirements in West Hampstead NW6 is essential for success.

Types of Rear Extensions in West Hampstead

single-storey Rear Extension: The most common and cost-effective option, extending the rear ground floor by 3-6 metres. These typically house kitchen-dining-living spaces with large glazed doors opening to the garden. Often combined with side return infills to maximise space.

two-storey Rear Extension: Adds space on both ground and first floors, ideal when you need additional bedrooms or bathrooms as well as ground-floor living space. More expensive and typically requires planning permission but offers significant additional space.

Wraparound Extension: Combines rear and side return extensions in a single project, creating substantial additional space—often 40-60 square metres. Popular in West Hampstead terraces where both opportunities exist.

Full-Width Extension: Extends across the entire width of the rear elevation rather than just one side, creating impressive open-plan spaces. Requires more substantial structural work as multiple walls are affected.

Planning Permission in Camden

West Hampstead falls within Camden Council's jurisdiction. Many rear extensions can be built under permitted development rights, but there are specific criteria:

Permitted Development for single-storey Extensions:

• Maximum depth of 3 metres for attached houses (like terraces)
• Maximum depth of 4 metres for detached houses
• Maximum height of 4 metres
• Maximum eaves height of 3 metres
• Extension cannot cover more than half the garden area
• No verandas, balconies, or raised platforms
• Materials should match existing house appearance

When Planning Permission is Required:

• Extension exceeds permitted development limits
• Property is in a conservation area (parts of West Hampstead are)
• Listed building
• two-storey extensions always require planning permission
• Previous permitted development rights have been used
• You want to extend beyond permitted development limits

Larger single-storey Extensions: Camden Council's guidelines allow single-storey rear extensions up to 6 metres for terraced houses through a relaxation of permitted development, but this requires a neighbour notification process. Adjoining neighbours have 21 days to comment, and if they object, the council decides whether to allow the extension.

Design Considerations for Maximum Impact

Creating Open-Plan Living: Most rear extensions involve removing the wall between the existing kitchen and dining room to create flowing open-plan space. This requires:

• Steel beam (RSJ) installation to support the structure above
• Structural engineer calculations and drawings
• Building control approval
• Careful consideration of how spaces will flow together

Roof Design and Natural Light:

Flat Roof with Rooflights: The most popular choice in West Hampstead. Large rooflights flood the space with natural light from above. Modern flat roofs use high-performance EPDM or GRP membranes with excellent longevity. Ensure proper drainage design—water must flow away efficiently.

Pitched Roof: Can look more traditional and blend better with period properties. However, this reduces ceiling height and limits rooflight options. Sometimes preferred or required in conservation areas.

Hybrid Design: Combining pitched elements with flat roof sections and glazing creates architectural interest while maximising light. Popular in contemporary designs.

Glazing Strategy: Large glazed doors are the defining feature of modern rear extensions:

• Bi-Fold Doors: Multiple panels that fold to one or both sides, opening up to 90% of the width
• Sliding Doors: Sleeker profile with large glass panels that slide behind each other
• Sliding-Pivot Systems: Modern designs where doors slide then pivot, creating wide openings
• Floor-to-Ceiling Glass: Maximises light and creates seamless garden connection

Invest in high-quality aluminium frames with slim sightlines—they're more expensive than UPVC but offer better aesthetics, durability, and thermal performance.

Structural Considerations

West Hampstead's Victorian and Edwardian properties have specific structural characteristics:

Foundations: Original houses typically have shallow brick foundations. Extensions require proper strip foundations, usually 0.9-1.2 metres deep depending on ground conditions. Clay soil common in West Hampstead requires particular attention as it moves with moisture changes.

Load-Bearing Walls: Removing rear walls to create open-plan spaces requires steel beams to carry the load of floors and roof above. Your structural engineer will calculate the required beam size based on span and loads.

Floor Levels: Matching new extension floors to existing house floors requires careful planning. Underfloor heating typically raises floor levels by 50-70mm, which must be accounted for.

Roof Connection: How the extension roof meets the existing house is critical for waterproofing. Lead flashing and proper detailing prevent leaks.

Maximising Space and Light

Design strategies to make your extension feel spacious and bright:

• Multiple Rooflights: Don't skimp—install at least two large rooflights, more if space allows
• Side Windows: If you're extending into a side return, windows in the side wall add extra light
• High Ceilings: Maximise ceiling height within planning limits—2.7-3 metres feels spacious
• Light Colours: White or light walls, ceilings, and floors reflect maximum light
• Minimal Upper Cabinets: In kitchens, keep walls clear to avoid blocking light
• Polished Floors: Reflective flooring surfaces bounce light around the space
• Internal Windows: Glazed doors or windows between the extension and hallway borrow light

Heating and Insulation

Modern building regulations require high thermal performance:

Underfloor Heating: The preferred choice for extensions. Provides even warmth without radiators, works efficiently at lower temperatures (ideal for heat pumps), and keeps walls clear for furniture. Electric systems are cheaper to install but more expensive to run; wet systems connected to your boiler or heat pump are more efficient for larger areas.

Insulation Standards: Walls, roof, and floors must meet current building regulations:

• Wall insulation achieving U-values of 0.18-0.28 W/m²K
• Roof insulation achieving 0.15-0.18 W/m²K
• Floor insulation achieving 0.22 W/m²K
• High-performance glazing with U-values of 1.4-1.6 W/m²K

These standards ensure your extension is comfortable and energy-efficient year-round.

Cost Breakdown for West Hampstead Extensions

Costs vary significantly based on size, specification, and ground conditions:

single-storey Rear Extension (20-25 sq m): £45,000-£70,000

• Basic to mid-range specification
• Standard finishes
• Quality bi-fold doors
• Two rooflights
• Underfloor heating

Side Return and Rear Extension (35-45 sq m): £70,000-£110,000

• Mid to high specification
• Premium glazing systems
• Multiple large rooflights
• Quality kitchen included
• High-end finishes

two-storey Extension (40-50 sq m): £90,000-£150,000+

• Ground floor and first floor addition
• Additional bathroom upstairs
• More complex structural work
• Scaffolding and roof work
• Quality finishes throughout

Budget approximately £2,200-£3,000 per square metre as a general guide, with premium specifications and complex builds at the higher end.

Party Wall Agreements

Terraced and semi-detached properties in West Hampstead require party wall agreements:

The Process:

1. Serve party wall notices to adjoining neighbours 2 months before starting work
2. Include drawings and details of proposed work
3. Neighbours can consent or appoint a surveyor (at your expense)
4. Create a schedule of condition recording the state of neighbouring properties
5. Agree a party wall award detailing the work and protections

Budget £1,500-£3,500 for party wall surveyor fees depending on complexity and whether neighbours appoint their own surveyors.

Construction Timeline

Typical timelines for rear extensions in West Hampstead:

1. Design and Planning (8-16 weeks): Architectural design, structural calculations, planning application if required
2. Party Wall Process (8-10 weeks): Running alongside design/planning phases
3. Pre-Construction (2-3 weeks): Ordering materials, site setup, final preparations
4. Groundworks (2-3 weeks): Excavating foundations, pouring concrete
5. Build Structure (4-6 weeks): Building walls, installing roof, windows, and doors
6. First Fix (2-3 weeks): Electrical, plumbing, heating installation
7. Second Fix (4-5 weeks): Plastering, kitchen installation, flooring, decoration

Total time: 5-8 months from initial design to completion, with 12-16 weeks of construction work.

Adding Value to Your West Hampstead Property

Well-executed rear extensions typically add more value than their cost:

• single-storey extension: adds £50,000-£90,000 to property value
• two-storey extension: adds £80,000-£140,000+ to property value
• Often achieve 100-150% return on investment
• Makes property significantly more marketable
• Reduces time on market when selling
• Improves quality of life and home enjoyment

The key to maximising value is quality design and execution—cutting corners saves little and compromises results.

Common Mistakes to Avoid

• Insufficient Light: Skimping on rooflights and glazing creates dark spaces—invest in maximum light
• Poor Quality Doors: Cheap bi-folds fail quickly—buy quality for daily use
• Inadequate Heating: Glazed spaces need proper heating design
• Drainage Problems: Flat roofs must have effective drainage—poor design causes leaks
• Ignoring Building Regulations: Thermal performance, structural requirements, and fire safety are mandatory
• Skipping Party Wall: Starting without agreements risks legal action and delays