Architects, Engineers, Surveyors & Builders Under One Roof.
Surveyor-led refurbishment advice via Hampstead Chartered Surveyors →One Studio. One Contract. One Team.
We deliver Chelsea side return extensions with extension designers, engineers and builders under one fixed-price contract - planning, structural design, party wall coordination, procurement, directly managed site teams, Building Control and final handover through one accountable team.
Every side return extension project in Chelsea is designed to respect the Chelsea Conservation Area and the character of Georgian townhouses, Victorian stuccoed villas, Chelsea mansion flats. Our in-house RIBA 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.
Chelsea 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 side return extension projects in Chelsea 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.
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 Chelsea streets including Cadogan Square, Carlyle Square, Chelsea Park Gardens, Chelsea Square, Glebe Place and the King’s Road, 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 - Article 4 Directions in Conservation Areas (register of directions by street) (2026); Rear extension — single storey (Resi rear extension cost guide, Oct 2025) (2026)
Victorian and Edwardian terraces were built with a narrow alley beside the rear closet wing — dead space that collects bins and shade. A side return infill claims that strip and folds it into the kitchen, turning a dark galley into a full-width room without losing any garden. A small footprint holds a dense engineering problem: building against a neighbour’s wall, removing your own flank wall, and re-routing the drainage that almost always runs down that alley.
Five stages, with the boundary and structural questions answered before anything is demolished.
Expect 12–20 weeks on site from groundworks to practical completion. Read the full side return extension guide for roof options, glazing comparisons and terrace case detail.
Because the work happens on or beside the boundary, the Party Wall etc. Act 1996 shapes the timetable of nearly every side return: building at the line of junction, cutting into the party wall for steel bearings and excavating near a neighbour’s footings each trigger their own notice, and if an adjoining owner dissents, a surveyor’s award must be in place before that element starts. Building Regulations approval is needed whatever the planning route. Our planning guide library covers the consent picture borough by borough.
Side returns punish loose coordination: the steel, the boundary and the neighbour relationship all have to be managed by people who talk to each other daily. Here the design comes from our in-house RIBA Chartered Architects, the structural calculations are produced in-house, and RICS surveying support for party wall and condition matters comes through our sister company, Hampstead Chartered Surveyors. You get one fixed-price JCT contract backed by £10M public liability cover, a 12-month defects period and a 10-year structural warranty. Enquire before 2pm on a weekday and we respond the same day.
Visit our studio or invite us to survey your home. We’ll assess scope, discuss design possibilities and provide an honest budget framework — completely free.
We survey your property, discuss your vision and provide a clear budget framework.