Extending a Kensington house means designing within Holland Park and the garden-square conservation areas. TrustBuilt Projects builds rear, lower-ground and structurally glazed garden extensions across W8 and SW7 — from the stucco terraces around Cornwall and Stanford Gardens to the Phillimore Estate below Campden Hill — all managed by us to the standard the Royal Borough expects.
Kensington's stock is dominated by tall white-stucco garden-square terraces — Cornwall Gardens, Stanford Gardens, Cottesmore and Lexham Gardens — plus the brick-and-stucco streets of the Phillimore Estate beneath Campden Hill and the mansion flats off Kensington High Street. On a garden-square house the only realistic way to add living space is at the rear: a single-storey or lower-ground extension opening onto the garden, leaving the protected front and the square itself untouched.
Most of W8 and SW7 sits inside the Royal Borough's conservation areas, and the communal garden squares carry their own protection on top, so an extension here is almost always a full planning matter rather than permitted development. The Royal Borough guards rear gardens and the green setting of the squares closely, which is why we keep additions modest, glazed where it brings daylight deep into the plan, and clearly subordinate to the original house.
Many Kensington homes are flats within converted stucco terraces or purpose-built mansion blocks, where extension scope is limited and lease and freeholder consent matter as much as planning. For houses, the party-wall position with neighbours on both sides is the practical constraint, and getting muck-away and deliveries off a garden square needs planning. We coordinate the architect, the structural engineer and the consents before any work is priced.
Kensington extension costs reflect the scale of these garden-square houses, the glazing quality owners expect onto the garden, and the conservation detailing the Royal Borough requires. Typical ranges:
| Project type | Typical cost | Timeline |
|---|---|---|
| Side-return extension | £70,000 – £120,000 | 14–22 weeks |
| Rear extension (single-storey) | £75,000 – £130,000 | 14–22 weeks |
| Structural-glazed / garden extension | £100,000 – £180,000 | 18–28 weeks |
| Lower-ground / vault extension | from £140,000 | 20–32 weeks |
Every project is quoted in writing after a free site visit — these ranges are a guide only.
Almost certainly. Nearly all of W8 and SW7 sits within a conservation area, and the garden squares carry extra protection, so permitted development rights are usually restricted — most rear and lower-ground extensions need full planning permission, and any listed house also needs listed building consent. We confirm the route for your address at the free site visit.
Scope is limited in mansion flats and converted stucco terraces, and lease terms and freeholder consent usually matter as much as planning. We're honest at survey stage about what's achievable — often the real gains are internal reconfiguration and a high-spec refit rather than a footprint extension — and we handle the building-management requirements that come with block work.
A rear or lower-ground extension onto the garden, frequently with structural glazing for daylight, adds the most usable space while leaving the protected stucco frontage and the square untouched. Side-returns are rarer here than on a South London terrace because of the way these houses are planned. We design to what your specific house and its setting will support.
Carefully — muck-away, deliveries and skips all need managing where a house backs onto a communal square or sits on a narrow Phillimore Estate street. We set the logistics out in the programme and serve the Party Wall notices to neighbours on both sides, so the build runs without conflict.
Free site visit, no obligation, written quote.
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