Exclusive Builders in Kensington
High-specification refurbishment, conservation-area and listed building work and basements in Kensington, under a JCT contract at a fixed, itemised price.
Builders in Kensington, W8
Kensington is Victorian stucco terraces and garden squares, red-brick mansion blocks and mews houses behind the main streets. Planning and listed building applications are decided by the Royal Borough of Kensington and Chelsea, whose conservation areas here include Kensington, Kensington Square, Kensington Palace, Kensington Court and De Vere. Schemes tend to be architect-led, combining a full refurbishment with work below ground or at the back of the house.
Alstruct takes on this work as main contractor. We price from your architect's or interior designer's drawings and specification after a site visit, build under a JCT contract for a fixed, itemised sum, and start controlled work only once the consents it needs are in place. Our published case studies are elsewhere in London (Archway, Bow, Limehouse, Golders Green, Cockfosters and Stratford), not in Kensington.
The high-specification refurbishment section below sets out the consents a Kensington project usually needs, including the borough's basement policy, and the published rates we use as a cross-check. If you already have drawings, see how pricing from your drawings works.
How we take on work in Kensington
- Main contractor under a JCT contract, as standard
- Fixed, itemised price from your design team's drawings, after a site visit
- Written variation instructions, with any extra cost confirmed before the work is done
- A dedicated site manager coordinating the trades and Building Regulations inspections
- £10M public liability insurance
- CHAS Elite, Constructionline Gold & FMB accredited
- 10-year workmanship warranty
- Drawings and photos can be attached to the enquiry form (PDF, JPG, PNG, HEIC, DWG)
Ultra-Premium Construction Services in Kensington
Extensions in Kensington
Rear and closet-wing extensions built to consented drawings, with the steelwork, glazing and finishes your architect specifies.
Learn more →Loft Conversions in Kensington
Mansard and roof-level conversions where planning and listed building consent allow, including the structural work, stairs and fit-out.
Learn more →Refurbishment in Kensington
Whole-house and apartment refurbishment in Kensington: structural alterations, new services, joinery, stone and decoration, built to your designer's schedule under one JCT contract.
Learn more →Basement Conversions in Kensington
Cellar conversions and single-storey basement excavation where the Royal Borough's basement policy and the building's listing allow, including underpinning, waterproofing and fit-out.
Learn more →Structural Works in Kensington
Underpinning, foundations, drainage and structural alterations, designed by your engineer and inspected by building control.
Learn more →Hard Landscaping in Kensington
Stone paving, garden walls, steps and front-area repairs, usually carried out as part of a wider refurbishment.
Learn more →House and kitchen extensions in Kensington
Kensington is Victorian stucco terraces and garden squares around Kensington Church Street and Holland Park, mews houses, and mansion flats along Kensington High Street. Kensington extensions are mostly lower-ground and basement projects, rear closet-wing infills and mews conversions, designed around listed building and conservation requirements.
Budget guidance for Kensington: expect £2,500–£4,000 per m² for a single-storey extension, which puts a 25–30 m² kitchen extension at £75,000–£120,000; two-storey and wraparound schemes are priced on the structure involved (see our house extension cost guide). Kensington's conservation areas include Kensington, Kensington Square, Kensington Palace, Kensington Court and De Vere, the borough has over 3,800 listed buildings, and the Royal Borough of Kensington and Chelsea applies a strict basement policy. Where approval from the Royal Borough of Kensington and Chelsea is needed, our design team prepares and submits the application.
Planning a kitchen extension? See our kitchen extensions page for layouts, glazing and costs.
Loft conversions in Kensington
Roof extensions are mansards or reconfigured top floors where a terrace allows them; Local Plan Policy CD12 resists extra storeys on unimpaired terraces and on buildings that already have a mansard.
Typical London figures are £25,000–£45,000 for a Velux conversion, £45,000–£75,000 for a dormer and £60,000–£100,000+ for a mansard (details in our loft conversion cost guide). Every Kensington loft quote follows a measured survey of the roof, head height and stair position, and includes Building Regulations sign-off, fire doors and structural calculations.
Renovations and refurbishment in Kensington
Kensington projects are high-end refurbishments of townhouses, mews houses and lateral apartments with bespoke joinery and full services. Typical Kensington refurbishments include structural openings with steel beams, new kitchens and bathrooms, rewiring, heating and period repairs such as sash windows, cornices and floors. Budgets are set out in our renovation cost guide; in Kensington, as everywhere, we work to a JCT contract, a written specification and a 10-year workmanship warranty.
High-specification refurbishment in Kensington
Kensington's housing is Victorian stucco terraces and garden squares, red-brick mansion blocks, and mews houses behind the main streets. Schemes here tend to be architect-led, combining a full refurbishment with work below ground or at the back of the house.
The Royal Borough of Kensington and Chelsea decides planning and listed building applications. The council says nearly three quarters of the borough is protected by 38 conservation areas, among them Kensington, Kensington Square, Kensington Palace, Kensington Court and De Vere. When a building is listed, the council says, all of it is protected, including the inside and any later extensions.
The borough's basement policy is the strictest rule most Kensington schemes meet. The Local Plan requires basement development to:
- cover no more than 50 per cent of each garden or open part of the site
- comprise no more than one storey
- add no further basement floors where a basement already has planning permission or was built under permitted development rights
- involve no excavation underneath a listed building, including vaults
Under the borough's Code of Construction Practice, basement excavation puts a site in Category 1: a Site Construction Management Plan must be approved before work starts, a Section 61 consent application is required, and a Construction Bond is paid to cover the council's monitoring. Work audible at the site boundary is permitted from 8am to 6pm, Monday to Friday, and at no time on Saturdays, Sundays or public holidays. Demolition and concrete-breaking are held to 9am to noon and 2pm to 5.30pm.
We build under a JCT contract for a fixed, itemised price taken from your design team's drawings, and we work with your architect or interior designer throughout. Alstruct carries £10M public liability insurance, holds CHAS Elite, Constructionline Gold and FMB accreditation, and gives a 10-year workmanship warranty. See pricing from your drawings and our high-end residential builders page.
Our published guides put a full basement excavation at £4,500–£6,500 per square metre, extensions at £3,200–£4,500/m² for high-spec work and £4,500–£6,000+/m² for the top tier, and a high-specification renovation of a Victorian terrace at £1,100–£1,600/sqm. Treat them as a sense-check: a Kensington project is priced from its drawings. Extension figures include VAT; basement and renovation figures exclude it.
Guides for homes in Kensington
For the period townhouses, mews and conservation areas of Kensington, our most useful guides are mansard loft conversion costs, basement conversion costs, extending in a conservation area, leaking lead roof valleys and damp basements and tanking.
Planning approvals in Kensington
Official government figures show the Royal Borough of Kensington and Chelsea approved 93.7% of householder planning applications decided between July 2025 and June 2026, against 85.8% across London.
See how every London borough compares, including loft and extension approval rates, in our 2026 London planning approvals study.
Alstruct projects near Kensington
Notting Hill Villa, W11
Every lead valley renewed on a period villa roof, and the basement store waterproofed and reinstated.
View project →Hammersmith Terrace, W6
A terraced house reworked from the lower ground floor to a new loft floor, with a new steel frame and a full refit.
View project →Archway Victorian Terrace, N19
Full Victorian terrace renovation and rear extension with triple glazing and aluminium sliding doors.
View project →Beyond the projects above, we have recent and current sites in W4, W14, NW8, NW6, W12 and SW6 within about five miles of Kensington, and we work across every London borough from our office in South Woodford, E18. See all completed projects →
Common questions about building in Kensington
Do I need planning permission for an extension in Kensington?
Houses (not flats or maisonettes) keep national permitted development rights for a single-storey rear extension of 3m attached or 4m detached, or up to 6m or 8m through prior approval, and most rear dormers within 40 or 50 cubic metres. The Royal Borough of Kensington and Chelsea's conservation areas here include Kensington, Kensington Square, Kensington Palace, Kensington Court and De Vere. Inside them, single-storey rear extension rights remain, but side extensions, two-storey rear extensions, cladding and roof additions need permission. Article 4 directions on named streets control windows, doors, boundary walls and roof coverings, and a borough-wide direction covers every basement.
What does the Royal Borough expect for mansards and roof extensions in Kensington?
Local Plan 2024 Policy CD12 resists additional storeys on complete terraces with an unimpaired roofline, on buildings that already have a mansard or extra storey, and where the roof itself is of historic interest; original dormers of interest should be kept. Policy CD13 adds that extensions must be subordinate. In a conservation area a full planning application is needed, and on a listed house the whole building, inside and out, is protected, so smaller works can need listed building consent too.
What does a mansard loft conversion cost in Kensington?
Our published London figures are £60,000–£100,000+ including VAT for a mansard loft conversion, with prime central schemes at £120,000–£150,000. On Kensington's stucco terraces and mews houses, the party walls, the parapet and whether the roofline is already broken all affect both the design and the cost. Our mansard loft conversion cost guide explains what is included.
Which Alstruct projects are nearest to Kensington?
Notting Hill Villa, W11, about 1.0 mile away, is our closest: every lead valley on a period villa roof was renewed and the basement store waterproofed and reinstated. Hammersmith Terrace, W6, about 1.6 miles away, was a terraced house reworked from the lower ground floor to a new loft floor, with a new steel frame and a full refit. Archway Victorian Terrace, N19, about 5.2 miles away, was a full Victorian terrace renovation and rear extension with triple glazing and aluminium sliding doors.
Which parts of Kensington do you cover?
We cover Kensington in W8, including the terraces and garden squares around Kensington Church Street, the Holland Park edge, the mews houses and the mansion flats along Kensington High Street. The Royal Borough of Kensington and Chelsea decides planning and listed building applications. We work from South Woodford, E18, about 11 miles away, and nearby we also cover Notting Hill, Chelsea and Hammersmith.
Nearby areas we cover
Alstruct works across every London borough. Here are areas close to Kensington with dedicated local pages: