House
extensions
in Knightsbridge, SW1X / SW7
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 Knightsbridge house extensions across Knightsbridge, Wilton Place, Lowndes Square - side-return, rear, wraparound and double-storey additions for Regency townhouses, Estate-Owned terraces and Prime Mansion Blocks where planning strategy, conservation detailing, Party Wall sequencing and structural engineering need handling properly.
House Extensions in Knightsbridge: What You Need to Know
Every house extension project in Knightsbridge is designed to respect the Knightsbridge Conservation Area and the character of Regency townhouses, estate-owned terraces, prime mansion blocks. Our in-house RIBA Chartered Architects handle Westminster, 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.
In Knightsbridge's conservation area, extensions must be designed with exceptional sensitivity. Westminster officers assess impact on the host building, neighbouring properties, and the wider streetscape. We secure planning approval through design excellence and thorough pre-application engagement.
International luxury quarter between Hyde Park and South Kensington. Mix of grand period buildings and modern luxury developments. Split between Westminster and RBKC. Our extensions in Knightsbridge use materials and detailing that complement the existing architecture — whether matching traditional brickwork and stonework or introducing high-quality contemporary glazing and zinc cladding.
An extension is, by definition, external change — and in Knightsbridge, Kensington and Chelsea scrutinises external change closely, estate consent runs alongside planning, and the prime mansion blocks add freeholder and party-wall layers of their own. Approvals and engineering are the dominant levers on any scheme here, so we lead with both. Nothing about that is a formality, and we have learned to treat none of it as one.
The houses being extended are serious buildings in serious company. Wilton Place and Montpelier Square hold elegant Regency and Victorian houses, while Lowndes Square and Cadogan Place carry grand stuccoed and red-brick terraces — and every one of them shares walls with neighbours whose properties rank among the most valuable in London. Party-wall strategy is not paperwork here; it is a design input from the first sketch.
Against that backdrop the London-wide bands are only a floor: £71,250–£112,500 excluding VAT for a single-storey rear extension, and an indicative £100,000–£200,000 for a wraparound. What a Knightsbridge extension finally costs is set by the consents won and the engineering needed to build politely between high-value neighbours.
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
We hold £10 million public liability insurance with Aviva; the certificate is available on request.
House Extensions in Knightsbridge: Questions
Will RBKC approve a house extension in Knightsbridge?
Only a well-argued one. Kensington and Chelsea scrutinises external change closely, estate consent runs alongside planning, and the mansion blocks nearby add freeholder and party-wall layers — so a Knightsbridge extension application is built as a full consents case, not a standard householder submission.
How much does a house extension cost in Knightsbridge?
The London-wide floor is £71,250–£112,500 excluding VAT for a single-storey rear extension and £90,000–£120,000 excluding VAT for a side return. Knightsbridge schemes typically sit above the mid-point of those bands once specification and consent workload are counted, and we quote each one from its own drawings.
Which Knightsbridge houses lend themselves to extension?
The elegant Regency and Victorian houses of Wilton Place and Montpelier Square are the classic candidates, with the grand stuccoed and red-brick terraces of Lowndes Square and Cadogan Place presenting grander — and more constrained — opportunities. Each street has its own rear condition, and we assess plot by plot.
Is a wraparound extension realistic in Knightsbridge?
Where the plot and the consents allow, yes — the London-wide indicative band for a wraparound is £100,000–£200,000. The determining factor in Knightsbridge is rarely budget; it is what the planning and estate framework will support on your particular corner of the district.
Can a listed Knightsbridge house be extended at all?
Sometimes — but the route is longer. Many Knightsbridge buildings are listed, leasehold or estate-controlled, so an extension to one involves heritage consent and, often, the estate's own approval on top of planning. We establish that full stack before advising whether the extension is worth pursuing.
Recent Projects Near Knightsbridge
Local character & heritage: extending in Knightsbridge
Knightsbridge sits in the City of Westminster and the Royal Borough of Kensington & Chelsea, and extending here means working with grand stucco and red-brick mansion flats and townhouses. 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 Knightsbridge's conservation areas, so most extensions need a full householder application, and most homes are high-value leasehold flats and a large share are listed. We design every extension to respect the period frontage and to win consent.
Knightsbridge heritage & architecture: Conservation areas · Roof developments & conservation · Listed buildings · Renovating a period terrace · Period facades · Facade planning rules
House Extensions in Knightsbridge: Planning & Local Context
the Royal Borough of Kensington & Chelsea · SW1X/SW7
Planning for house extensions in Knightsbridge
Rear and side-return extensions are popular in Knightsbridge, but permitted-development rights are frequently restricted within Knightsbridge'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
Knightsbridge SW1X/SW7 sits within Knightsbridge'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. Knightsbridge straddles the Royal Borough and Westminster, so the authority depends on the street. 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 Knightsbridge 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 Knightsbridge work: Chevalier House, Knightsbridge Rutland Court, Knightsbridge. Explore our Kitchen Renovation Loft Conversions in Knightsbridge, or the Knightsbridge hub · Refurbishment Company in Knightsbridge.
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 →
House Extensions in Nearby Areas
More Services in Knightsbridge
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We survey your property, discuss your vision and provide a clear budget framework.