Rear Extensions in Hampstead NW3. Rear extensions, side returns and wraparound extensions for georgian and victorian villas, large detached houses, period terraces and mansion flats. Camden planning experts. Expanding Hampstead's homes with heritage-sensitive design.
House extensions in Hampstead — rear, side return, and wraparound — are the most effective way to add living space without moving. The georgian and victorian villas, large detached houses, period terraces and mansion flats common in Hampstead typically offer strong extension potential.
Hampstead's conservation area status means extensions must be sensitively designed. Camden expects extensions to use matching or complementary materials and to respect the scale and character of the original building. We navigate these requirements daily.
London's most prestigious village with Flask Walk, Church Row, and Frognal. Camden conservation area with strict planning controls. Home to listed buildings, heritage pubs, and the Heath. Side-return extensions are particularly popular in Hampstead's terraced streets, transforming narrow kitchen spaces into full-width open-plan living areas connected to the garden.
Camden · NW3
Hampstead is in a conservation area, which restricts permitted development rights for extensions. Side extensions, cladding changes, and some rear extensions require Camden planning permission. Rear extensions may still qualify under PD (up to 6m for terraced, 8m for detached) via the Prior Approval process, but Camden assesses neighbour impact before granting approval.
When permitted development doesn't apply in Hampstead, a full householder planning application is required (fee: £258). Camden determines applications within 8 weeks. Camden requires extensions to be subordinate to the host building, with matching materials and careful consideration of neighbour amenity. Our architects prepare applications that address Camden's specific assessment criteria, including design & access statements and heritage statements where required.
Camden notifies adjoining neighbours of all extension planning applications in Hampstead, with a 21-day consultation period. Neighbours can raise objections on planning grounds (loss of light, privacy, overbearing impact) — Camden officers assess these against the Camden Local Plan policies. Our pre-application design process considers neighbour impact from the outset, reducing objection risk and refusal grounds.
In Hampstead's conservation area, Camden requires extensions to match the host building's materials, proportions, and architectural detailing. Our architects specify matching brickwork (with lime mortar where appropriate), timber or metal windows to match existing profiles, and roofing materials that complement the streetscape.
Our in-house planning team has a 97% approval rate across Camden. View our planning track record →
Camden · NW3
More space, more light, more value — without moving. Our RIBA architects design extensions that transform how London homes function, while our in-house structural engineers and build teams deliver them on a fixed-price contract from foundation to final coat of paint. Rear, side-return, wraparound and double-storey — every type, every borough.
London's housing stock was built for a different era. Victorian terraces, Edwardian semis and inter-war villas were designed around formal rooms, separate kitchens and service corridors — layouts that don't suit contemporary family life. A well-designed extension replaces the cramped galley kitchen and disconnected dining room with a flowing, light-filled living space that connects the house to the garden and transforms daily life.
The most common London extension is the side-return — reclaiming the narrow alley that runs alongside the kitchen on a Victorian or Edwardian terrace. Combined with removing the wall to the dining room, this creates an open-plan kitchen-living-dining space of 30–45 square metres that fundamentally changes how the ground floor functions. But we build every extension type: full-width rear, side-return, wraparound (rear plus side), double-storey, and infill extensions that connect detached buildings.
Our integrated approach means one team handles every aspect: the RIBA architect designs the space, our structural engineers calculate the steelwork, our planning consultants navigate permitted development rules or conservation area restrictions, our RICS surveyors manage party wall matters, and our build team constructs the extension from foundation to final decoration. There's no coordination gap because there's no gap between firms.
Every extension starts with a free on-site consultation. We assess the site, discuss your brief, identify the planning route (permitted development or full application), check party wall implications and provide an honest budget indication — before any design fees are committed.
Each extension type suits different house layouts, plot shapes and budgets. We design and build all four — and advise honestly on which delivers the best return for your property.
Full-width or partial-width extension to the rear of the property. The workhorse of London extensions — creating open-plan kitchen-diners with direct garden access.
Infilling the narrow alley alongside Victorian and Edwardian terraces. London's most popular extension type — doubling kitchen width and creating a dramatic sense of space with a glazed roof.
Combining rear and side-return extensions into an L-shaped addition. Creates the maximum ground-floor space — typically 25–45 sqm — for a large open-plan kitchen-diner-family room.
Two-storey addition providing extra space on both ground and first floors. Typically a kitchen extension below with a bedroom or bathroom above. Requires planning permission in most cases.
Many house extensions can be built without planning permission under Permitted Development (PD). Here are the key rules for London homeowners.
Single-storey rear extensions: Up to 3 metres deep on attached houses (terraced and semi-detached) or 4 metres deep on detached houses, measured from the original rear wall. The extension must not exceed 4 metres in height and the eaves must not be higher than the existing eaves. These limits apply without any notification to the council.
Prior Notification (Larger Home Extension) scheme: Extends the PD limits to 6 metres (attached) or 8 metres (detached) for single-storey rear extensions. You must notify the council and your immediate neighbours before starting. The council has 42 days to determine whether prior approval is needed based on the impact on neighbours' amenity. If no response is received within 42 days, you may proceed.
Side extensions: A single-storey side extension must not exceed half the width of the original house. It must be no more than 4 metres in height and the eaves must match the existing. Materials should be similar in appearance to the original house.
Two-storey extensions: Permitted under PD up to a maximum 3-metre depth from the rear wall. Must not be within 7 metres of the rear boundary. The roof pitch must match the existing house. Cannot extend beyond the side wall of the original house.
Forward of the principal elevation: Extensions cannot project forward of the principal (front) elevation facing a highway. This is an absolute rule under PD with no exceptions.
Conservation area restrictions: Properties in conservation areas lose PD rights for side extensions and rear extensions visible from a public highway. Cladding the exterior and adding dormers on roof slopes facing the highway are also restricted. Article 4 directions can remove additional PD rights entirely. Always check your specific property's designations before assuming PD applies.
Extensions affect your neighbours. Understanding the legal framework protects both your project and your relationship with those next door.
The Party Wall etc. Act 1996 applies when your extension foundations are within 3 metres of a neighbouring building's wall — which covers virtually all terraced and semi-detached extensions. If your foundations go deeper than your neighbour's (common with basement-level extensions), the 6-metre rule applies instead. You must serve notice at least 2 months before work starts. We handle the entire process in-house at no additional cost.
Two-storey extensions can reduce daylight and sunlight to neighbouring windows. While the planning system considers amenity impact, the common law right to light is a separate legal issue. A neighbour can seek an injunction to prevent or remove a building that substantially reduces the light to their windows — even if planning permission was granted. For two-storey extensions near boundaries, we commission daylight/sunlight assessments (BRE guidelines) to quantify the impact and demonstrate compliance.
If your extension is built up to or astride the boundary line, a different type of party wall notice is required. Building astride the boundary (where the wall sits partly on each property) requires your neighbour's written consent. Building up to the boundary (entirely on your land) does not require consent but still requires notice. The position of the boundary — and the ownership of any existing boundary wall — should be confirmed before design work begins.
If you apply for planning permission, neighbours are notified and can submit comments during the consultation period (typically 21 days). Objections are considered by the planning officer but do not automatically prevent approval. Common objection grounds include loss of light, overlooking, noise and visual impact. Our applications pre-emptively address these concerns with detailed design justification, reducing the risk that objections influence the outcome.
Every extension requires building regulations approval — separate from planning permission. Here are the key Parts that affect house extensions in London.
The most impactful regulation for extensions. New walls, roofs, floors and glazing must achieve minimum U-values: walls 0.28 W/m2K, flat roofs 0.18 W/m2K, floors 0.22 W/m2K, windows 1.6 W/m2K. Extensions over 25% of the existing floor area may require SAP calculations to demonstrate whole-building energy performance. This typically means high-performance insulation and double or triple glazing as standard.
Extensions built within 1 metre of the boundary must have fire-resistant external walls (typically 1-hour fire rating). Windows and openings facing the boundary are restricted. If the extension creates a new habitable room above ground floor level, fire escape provisions must be considered — including window sizes and fire doors to the escape route.
Where an extension creates a new bedroom that shares a wall or floor with a room in an adjoining property, acoustic separation must meet minimum standards. This is particularly relevant for two-storey extensions on terraced houses where the new first-floor room shares a party wall with the neighbour's bedroom. Sound insulation testing may be required.
New ground floor extensions must have level or ramped thresholds (maximum 15mm upstand) at external doors to allow wheelchair access. Internal door openings should be minimum 775mm clear width. This regulation applies to all new extensions regardless of whether the occupants currently need accessible features — the building must be usable by future occupants.
SAP calculations: For larger extensions, a Standard Assessment Procedure (SAP) calculation may be required to demonstrate that the extension meets the energy targets set by Part L. We commission these calculations as part of the building regulations package and submit them alongside the structural and architectural drawings. The cost is typically £300–£500 and is included in our design-and-build projects.
A clear, structured process that takes the uncertainty out of extending your home.
We visit your property, measure the site, assess the garden, check party wall situations and discuss your brief in detail. We identify whether your extension falls within permitted development rights or requires planning permission, and flag any conservation area, Article 4 or tree preservation order constraints. You receive a written feasibility assessment with an indicative budget and recommended approach within 48 hours.
Our architects produce the extension layout with 3D visualisations. Structural engineers design the steelwork, foundations and connection details. We submit planning applications or lawful development certificates, building regulations packages and party wall notices in parallel. For design-and-build projects, the kitchen design, lighting scheme and material selections run concurrently so everything is resolved before construction starts.
Foundations are excavated and poured (typically strip or trench-fill), walls built to DPC level, floor slab laid and the structural shell erected — blockwork walls, steel beams, lintels and the roof structure. The opening between the existing house and the new extension is formed, with temporary propping supporting the existing structure until the steel beam is in position. Once the roof is weathertight, the extension is sealed and internal works begin.
Insulation, plasterboarding, first fix electrics and plumbing, underfloor heating, window and door installation, kitchen fit-out, tiling, flooring, second fix carpentry, painting and decoration. Bi-fold or sliding doors are installed connecting the extension to the garden. External works — patio, drainage, landscaping — complete the project. Building control conducts the final inspection and issues the completion certificate.
Guide prices for London house extensions. All prices are fixed and include design, engineering, planning, full build and decoration.
Infilling the side alley with a glazed roof. Doubles kitchen width and creates a bright, open-plan ground floor. 8–15 sqm added.
Full-width or partial rear extension with bi-fold doors to the garden. Creates a generous kitchen-diner-living space. 15–30 sqm added.
Combined rear and side extension creating an L-shaped addition. The largest single-storey extension option. 25–45 sqm added.
Two-storey extension — kitchen below, bedroom or bathroom above. Best sqm/cost ratio but requires full planning permission. 30–60 sqm total.
What separates a Hampstead Renovations extension from a standard builder's quote.
Every extension is designed by a RIBA architect to suit your specific house, site and lifestyle. No templates, no catalogue layouts — a bespoke design that maximises light, space and the connection between your home and garden.
Architects, structural engineers, planning consultants, party wall surveyors and build teams all under one roof. No subcontracted design, no outsourced engineering, no coordination gaps between separate firms. One team, one contract, one accountable party.
The price we quote is the price you pay. Not an estimate with provisional sums. Not a price that escalates when you choose your fixtures. A fixed, agreed total covering design, engineering, the full build and every material specified in the contract.
We've secured planning approvals across every inner London borough — including conservation areas in Camden, Islington, Westminster and Haringey with the most restrictive policies.
We maximise what can be achieved under PD rights — including the larger home extension scheme (up to 6m rear on terraces, 8m on detached) — avoiding planning costs and delays where possible.
Structural glass roofs, frameless glass corners, slim-profile aluminium bi-folds and floor-to-ceiling fixed glass. We design extensions that flood the ground floor with natural light.
Most extensions are kitchen-led. Our kitchen designers work alongside the architect from day one, ensuring the kitchen layout, island position and appliance locations drive the extension geometry — not the other way round.
RICS surveyors handle all party wall notices and agreements in-house. For terraced and semi-detached extensions, party walls are always a factor — our experience streamlines the process.
We install wet or electric underfloor heating beneath extension floors as standard on most projects — eliminating radiators and freeing up wall space in the new room.
In sensitive settings, we design extensions that satisfy conservation officers — using appropriate materials, roof forms and detailing that complement the existing building's character.
Patio, drainage, garden reinstatement and boundary work are part of the fixed-price contract — not treated as extras that inflate the final bill after the extension is built.
Selected house extensions completed by our team across London.
6m full-width rear extension with structural glass roof and 4m bi-fold doors. Open-plan kitchen-diner with island under permitted development.
L-shaped wraparound creating 38sqm open-plan kitchen-diner with glazed side return and full-width rear doors. Planning approved in conservation area.
Two-storey rear extension — open-plan kitchen below, master bedroom with en-suite above. Full planning permission secured through Haringey.
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Visit Hampstead On Demand →The side-return extension completely transformed our ground floor. What was a dark, narrow kitchen is now a bright, open-plan room with a huge skylight running the full length. The architect suggested the glazed corner detail that everyone comments on — that's the difference between a design-and-build firm and a standard builder's extension.
We were worried about getting planning for a wraparound in a conservation area. Hampstead Renovations designed an extension with zinc cladding and a recessed glass link that the conservation officer praised as exemplary. The build was immaculate and the fixed price held exactly — not a single extra charge in 14 weeks of construction.
Having the kitchen designer, architect and structural engineer all working together from the start meant our extension was designed around our kitchen — not the other way round. The island position, the sink location, the pendant lighting — everything was resolved before the builders dug the foundations. No compromises, no changes on site.
Everything London homeowners ask about house extensions.
Use these area-specific guide pages to compare the next build routes, planning questions and cost topics people commonly research in Hampstead NW3.
We visit your property, assess the site, discuss your brief and give you an honest feasibility assessment — including extension type, budget, timeline and planning route. No obligation.
We visit your property, measure the site and provide a clear assessment of what's achievable — completely free.
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