Walk down any Victorian terrace street in London and look at the side returns: those narrow strips of unused outdoor space between the kitchen and the boundary wall. For decades they served as bin stores, alleyways and afterthoughts. Today, they are the single most common extension project we deliver, and for good reason.
A typical Victorian or Edwardian terrace was built with a galley kitchen running along one side and a small yard alongside. Filling that yard with a thoughtful extension does three things at once: it widens your kitchen into a generous open-plan space, brings in light from above through rooflights or a glazed roof, and connects the house properly to the garden through bifold or sliding doors.
Cost: What to Budget
For a standard side-return extension on a London terrace in 2025, expect a build cost of £85,000 to £140,000 depending on size, finish level and ground conditions. That figure is for the structural shell, kitchen fit-out, glazing, electrics, plumbing and decorating, but excludes professional fees and VAT.
Add £8,000 to £15,000 for architect and structural engineer fees, party wall surveyor costs, and building control. Add a 10 percent contingency for unknowns. As a rule of thumb, budget around £3,200 to £4,000 per square metre for a quality finish.
Programme: How Long It Takes
A typical project runs 14 to 18 weeks on site once mobilised. Pre-construction, allow 4 to 6 months for design, planning, party wall agreements and tendering. The full journey from first sketch to handover is usually 9 to 12 months, sometimes longer if planning is contested.
Planning Traps to Avoid
Most side-return extensions fall under permitted development, but there are three traps we see clients fall into regularly:
- The 3-metre rule: single-storey rear extensions are limited to 3m beyond the original rear wall on terraces (4m on detached). Going beyond requires the prior approval process or full planning permission.
- Article 4 directions: many London conservation areas have removed permitted development rights. Always check before assuming you can build without full planning.
- Party wall: excavating within 3 metres of a neighbour's wall, or building up against it, triggers the Party Wall Act. Skipping this leads to expensive disputes mid-build.
Living Through It
Most clients stay in the house during the build, with the kitchen out of action for 6 to 8 weeks of the programme. We help set up a temporary kitchen on the ground floor or in a separate room. Plan for it. The clients who handle the disruption best are the ones who treat it as a known six-week inconvenience rather than a daily surprise.
"The single best decision a client makes is choosing a contractor before they finalise the design. Early contractor input saves more money than any value engineering exercise after the fact." James Whitaker, Managing Director.