Why the side return works
Victorian and Edwardian London terraces were built with a narrow alley alongside the rear closet wing, originally for ventilation and outside toilet access. In modern usage the alley is dead space — too narrow to plant, too overshadowed to enjoy, too awkward to use. Filling it as part of a kitchen extension recovers that area into the house and, crucially, widens the kitchen to match the front-room width. The result is a single open-plan space that runs front to back of the house with the kitchen, dining and family zones flowing into each other, capped at the garden end by a glazed wall. Done well, the side return is the most transformative extension type per pound spent.
Permitted development pathway
Most side returns on terraces fall under Class A permitted development as a single-storey rear extension. The PD allowance permits a depth of up to 3m beyond the original rear wall (under standard PD) or up to 6m under the Larger Home Extension prior approval route, with eaves up to 3m if within 2m of the boundary, and overall height up to 4m. The side return component itself isn't subject to a width restriction provided you're not extending beyond a side boundary. We almost always submit a Lawful Development Certificate alongside the build to provide legal proof for resale. Conservation areas and Article 4 zones (parts of Hackney, Islington, Camden, Westminster) usually require full planning even for modest side returns.
Roof options
The roof over a side return can be flat or pitched. Flat roofs are most common in London because they sit below the existing first-floor windows, preserving light and outlook to the rooms above. A flat roof is typically finished in EPDM, GRP or single-ply membrane, with a glazed rooflight or roof lantern set centrally for top-light into the kitchen. Pitched roofs work where the existing first-floor windows are positioned to clear the new ridge — usually only on properties with very high first-floor ceilings. We model both options at survey and recommend based on the existing window heights and the desired light distribution.
Rear glazing — bifold, slider or Crittall
The rear wall of a side return is usually 4–5 metres wide and demands generous glazing to connect the kitchen to the garden. Bi-folding doors give maximum opening in summer — a 4m bifold typically opens 80% of the wall, dropping the threshold to a continuous indoor-outdoor space. Sliding doors give larger fixed glass panels (better for winter views and slightly better thermal performance) but only open one third or half of the wall. Crittall-style steel-framed doors deliver an industrial aesthetic with very slim frames; they cost roughly 30–50% more than aluminium bifolds but transform the architectural character of the space. We supply and install all three; our preferred manufacturers are Schüco for sliders, Origin and Sunflex for bifolds, and Fabco Sanctuary or Crittall Windows for steel frames.
Structural method
The original side wall of the closet wing usually carries the wing's roof; removing this wall to open the side return into the kitchen requires a steel beam (typically 203 UC) spanning the full depth of the new extension, picking up loads from above. The rear wall of the closet wing is replaced with a second steel beam where it's removed for open-plan flow. Foundations are usually mass-fill concrete to 1m depth at the boundary wall (subject to ground conditions and tree presence — clay soils with mature trees nearby often need deeper foundations or piles). Party wall agreements are required with the side neighbour because we build off, or against, the boundary wall.
Kitchen integration
Most clients combine the side return with a full kitchen replacement. We work with five London kitchen suppliers — DesignSpace, Roundhouse, Smallbone, Plain English and IKEA Sektion (for budget-conscious projects with high-spec finishes) — and our team installs whichever the client selects. The kitchen layout typically runs an island parallel to the original closet wing line with the run of tall units against the new side wall and bifolds across the rear. Underfloor heating goes under polished concrete or large-format porcelain tile as standard, ensuring the wall space is freed for cabinetry and glazing rather than radiators.
Living through the build
A side return takes 10–16 weeks. The existing kitchen is decommissioned in week one and a temporary kitchen (microwave, induction hob, fridge, sink) is set up in another room. Most clients use the dining room or front lounge. Disruption peaks in weeks two through five (demolition, foundations, steels, brickwork) and decreases through the fit-out phase. We aim to have the new kitchen plumbed and operable by week 10–12 with finishes following.
