House
extensions
in Kensington, W8
Architects, Engineers, Surveyors & Builders Under One Roof.
One Studio. One Contract. One Team.
RICS surveying support for party walls, licence to alter, conservation-area works & neighbour mattersWe design and build Kensington house extensions across Kensington's principal residential streets - side-return, rear, wraparound and double-storey additions for Georgian townhouses, Stucco Italianate terraces and larger family homes where planning strategy, conservation detailing, Party Wall sequencing and structural engineering need handling properly.
House Extensions in Kensington: What You Need to Know
Every house extension project in Kensington is designed to respect the Kensington Conservation Area and the character of Georgian townhouses, stucco Italianate terraces, prime mansion flats. Our in-house RIBA Chartered Architects handle RBKC planning applications, our chartered structural engineers specify any load-bearing work, and our directly-employed trades deliver the build under one fixed-price contract. We coordinate Building Control, Party Wall awards where needed, and all certifications through to handover.
Kensington falls within a conservation area, which means visible external alterations require careful design and often full planning permission. Our architects have extensive experience securing approvals in RBKC's conservation areas.
Our house extension projects in Kensington are delivered by our in-house team of RIBA architects, structural engineers and specialist tradespeople. Every project is managed under a single fixed-price contract with no hidden costs.
House extensions in Kensington: what actually drives consent and buildability
Kensington W8 ranges from Kensington High Street and Notting Hill Gate edges to quiet residential cul-de-sacs, garden squares, white-stucco villas, mansion flats and mews houses. RBKC describes Kensington Conservation Area as the largest of the borough’s conservation areas, with building ages from early Georgian speculative development through to the present day.
RBKC publishes adopted conservation-area material for Kensington, Kensington Court, Kensington Palace and Kensington Square, so visible fabric, listed-building status, roof or basement work and facade changes need checking before scope is fixed. Leasehold flats also need freeholder or council approval and, often, a Licence to Alter for layout and services work.
Cost is shaped by W8 access logistics, mansion-flat acoustics, concealed service routes, waterproofing, conservation-grade plasterwork and joinery, period floors, party-wall awards and the approvals needed before work can start in listed, estate-controlled or leasehold buildings.
Planning a Kensington house extension? Send the address and outline scope and we will map W8 planning, heritage, party-wall and structural constraints before pricing. Tell us about your project →
House Extensions in Kensington: Applied to the Local Stock
Kensington sits in the Royal Borough of Kensington and Chelsea, within the Kensington Conservation Area, on some of the most valuable residential streets in London. RBKC Article 4 directions withdraw permitted development rights for small-scale external changes — replacing windows and front doors, removing or rebuilding boundary walls, roof coverings and other front-elevation works — at properties listed on Kensington streets including Kensington Square, Kensington Court Place and Kensington Church Street, so those works need planning permission. London-wide cost band for rear extension — single storey: £71,250–£112,500 excluding VAT (Resi rear extension cost guide, Oct 2025).
Sources: RBKC conservation area maps (register of the borough's 38 conservation areas) (2026); RBKC - Article 4 Directions in Conservation Areas (register of directions by street) (2026); Rear extension — single storey (Resi rear extension cost guide, Oct 2025) (2026)
What a House Extension Involves
An extension reshapes how the whole ground floor works, not just how big it is — the new structure, the opening into the existing house, the kitchen and the garden connection all have to be designed as one move. We take each project from feasibility drawings through consents, structure and fit-out under a single fixed-price contract. Most extensions we build include the scope below.
- Rear extensions — single-storey additions that open the back of the house to the garden
- Side-return & wraparound — infilling the side alley of a terrace, alone or combined with a rear addition
- Double-storey — new bedrooms or bathrooms above the ground-floor addition, designed to sit comfortably with the original roofline
- Foundations & steel — groundworks, beams and the opening into the existing house, engineered by our own structural team
- Glazing — rooflights, glazed roofs and slim-framed sliding or bi-fold doors specified for light and thermal performance
- Kitchen integration — the kitchen layout planned with the architecture from the first drawing, not squeezed in afterwards
- Services & heating — electrics, plumbing, drainage and underfloor heating built into the new floor
- External works — patio, drainage connections and garden reinstatement completed within the contract
How We Run Your Project
Six stages, with the consents and engineering settled before the first spade goes in.
- Feasibility visit — we assess the site, the boundaries and your brief, and identify the right consent route for your property.
- Design & approvals — our architects draw the scheme while planning or permitted development paperwork, structural calculations and party wall notices progress together.
- Fixed-price contract — every element specified and priced before construction, from foundations to door hardware.
- Groundworks & shell — excavation, foundations, walls, steel and roof, taken to weathertight while you carry on living in the house.
- Fit-out — insulation, services, glazing, kitchen, flooring and decoration, with the opening into the existing house formed once the shell is sealed.
- Completion — building control inspection, snagging, external works and handover with the full certification pack.
Read the full house extension guide for extension types, permitted development limits and the build programme stage by stage.
Many rear extensions can proceed under permitted development — broadly up to 3m deep on attached houses and 4m on detached, extendable to 6m and 8m through the prior approval scheme — but conservation areas, Article 4 directions and listed status change the picture, and every extension needs Building Regulations approval regardless of the planning route. Where foundations come within 3m of a neighbouring building, the Party Wall etc. Act 1996 obliges you to give adjoining owners a minimum of two months’ written notice before construction can begin. Our planning guide library sets out the rules for each borough.
Why Hampstead Renovations
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House Extensions in Kensington: Questions
Do permitted development rights still apply to house extensions in Kensington?
Less than owners expect. RBKC has made Article 4 directions that strip permitted development rights for external works — window and front-door replacement, boundary walls, roof coverings and other front-elevation changes — from properties on streets including Kensington Square, Kensington Court Place and Kensington Church Street. Across the borough, 38 conservation areas cover nearly three quarters of the land, and proposals within them must preserve or enhance historic character — so we plan Kensington extensions as full applications from the start.
What does the planning application for a Kensington extension involve?
Making the conservation case. Kensington lies within the Kensington Conservation Area, on some of the most valuable residential streets in London, and RBKC requires proposals in its conservation areas to preserve or enhance their historic or architectural character or appearance. That test is the spine of the application — and early command of the borough's rules is what keeps a Kensington application on course, so we resolve them before the design is committed.
Which Kensington houses lend themselves to extension?
Kensington's houses are grand Victorian and Georgian townhouses and stucco terraces gathered around Campden Hill, Kensington Church Street and the Phillimore and Pembroke estates; most are listed or of group value, and the area is largely leasehold, which shapes the consent route. The garden-square terraces of Pembroke and Phillimore Gardens are natural candidates for reconfiguration, of which an extension is often one part.
How much should I allow for a house extension in Kensington?
As London-wide bands excluding VAT: £71,250–£112,500 for a single-storey rear extension and £90,000–£120,000 for a side return. A Kensington scheme is then priced against its own design and consents rather than against the headline range.
Who else, besides RBKC, must approve a Kensington house extension?
Often the estate or the freeholder. In Kensington, estate and freeholder consent runs alongside the planning decision, and where the property is a leasehold flat, freeholder or council approval — frequently a Licence to Alter covering layout and services work — is needed as well. We run those consents in parallel with the RBKC application so the programme stays whole.
Recent Projects Near Kensington
Local character & heritage: extending in Kensington
Kensington sits in the Royal Borough of Kensington & Chelsea, and extending here means working with grand white-stucco townhouses and garden squares. Where houses and gardens allow, side-return and rear extensions open up the living space; in the many flats, the equivalent is internal reconfiguration and, where possible, lower-ground additions.
Permitted-development rights are usually restricted in Kensington's conservation areas, so most extensions need a full householder application, and a very high proportion are listed and the borough operates a strict basement policy. We design every extension to respect the period frontage and to win consent.
Kensington heritage & architecture: Conservation areas · Roof developments & conservation · Listed buildings · Renovating a period terrace · Period facades · Facade planning rules
House Extensions in Kensington: Planning & Local Context
the Royal Borough of Kensington & Chelsea · W8
Planning for house extensions in Kensington
Rear and side-return extensions are popular in Kensington, but permitted-development rights are frequently restricted within Kensington's conservation areas, so most extensions need a full planning application to the Royal Borough of Kensington & Chelsea with design that respects the prevailing building line and materials.
the Royal Borough of Kensington & Chelsea context
Kensington W8 sits within Kensington's conservation areas, and the Royal Borough operates one of the country's strictest planning regimes — its basement policy limits excavation to a single storey beneath the footprint, and listed-building and conservation control is extensive. Our in-house RIBA Chartered Architects prepare and submit every application to the Royal Borough of Kensington & Chelsea and handle pre-application discussions where early planning advice is useful.
Building Regulations
House Extensions in Kensington must satisfy Building Regulations — covering structural design to Part A, thermal performance to Part L, and drainage and foundations agreed with Building Control. Our in-house engineers manage Building Control from initial notice to completion certificate.
Recent work & local links
See recent Kensington work: Gloucester Road, Kensington Pembroke Gardens, Kensington. Explore our Kitchen Renovation Loft Conversions in Kensington, or the Kensington hub · Refurbishment Company in Kensington.
Our in-house planning team prepares and submits every the Royal Borough of Kensington & Chelsea application and manages building control end to end. View our planning track record →
More Services in Kensington
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