A kitchen extension in Wandsworth Town is really about the back of the house. The classic Victorian terrace here keeps its kitchen in a narrow rear back-addition, with a closet wing beyond it and a dark side return alongside — a cellular, poorly lit arrangement that no longer suits how people cook and eat. The move that transforms it is the wrap-around: infilling the side return to gain width and adding a modest projection across the rear to gain depth, so the old kitchen, the closet wing and the alley become a single kitchen-diner. That is a different problem from a straight rear extension, because the room ends up broad and deep, and the middle of the new plan sits furthest from any window. It is also why a kitchen extension here has to be designed as a room, not just a footprint: the width you gain from the side infill is only useful if the layout, the daylight and the services are resolved together, and that is where most of the design effort actually goes.
That geometry makes daylight the governing question. Once a kitchen-diner spreads across the full ground-floor width, the centre of it can turn gloomy unless light is brought in from above. We resolve this with roof glazing tuned to the room — a lantern set over the dining zone, or a run of flush rooflights across the flat roof of the infill — so the deepest part of the plan, where the old closet wing stood, is the brightest rather than the darkest. The rear glazing to the garden handles the far end, but it is the roof light over the middle that stops a wide kitchen-diner reading as a dim back room, and we position it in section against the ridge and the neighbour boundary.
The kitchen-diner is also a layout problem more than a footprint one. Unlike a spare rear reception, a kitchen has to hold a working triangle, an island or run of units, a dining table and often a sitting corner, all with clear sightlines through to the garden. We set the island and the appliance run first, because they fix where the daylight, the services and the circulation have to land, then design the extension envelope around that plan rather than drawing a box and fitting a kitchen into it afterwards. Getting the threshold to the garden flush, and lining the island up with the roof light and the rear doors, is what makes the finished room feel like one space rather than an old house with a lump added on the back.
A kitchen is the most service-heavy room in the house, and relocating it to a new rear extension moves all of that with it. The sink, dishwasher and any utility appliances need drainage that falls correctly to the existing soil and waste connections — often where the old closet-wing stack sat — and the run has to be planned before the slab is poured, not chased in later. The hob needs mechanical extract ducted to an external wall or through the roof, and the whole floor is usually the place to lay underfloor heating over the new insulated slab. We coordinate the drainage, extract, gas and electrical routes at design stage so the structural and finish decisions above them are not compromised by services discovered on site. A misplaced soil run or an extract duct fighting the roof glazing is expensive to fix once the slab is down, so this coordination is done on the drawings, where the fall of a waste pipe and the position of a rooflight can still be reconciled cheaply.
Opening the back of the house also engages structure and the neighbours. Removing the rear wall and the closet-wing walls to make the kitchen-diner continuous usually needs steel beams sized by a structural engineer to carry the floors and roof above, with the new corner posts and padstones coordinated into the layout so they do not land in the middle of the island. Where the extension reaches the boundary with the adjoining terrace, the Party Wall etc. Act 1996 applies, and building regulations govern the new structure, the thermal performance of the walls and roof, ventilation to the kitchen, drainage and the glazed elements. Temporary support during the opening-up, the interface between the new steel and the retained masonry, and the sequence of taking down the closet-wing walls all have to be thought through in advance. We build all of this into the drawings so it is resolved on paper before it becomes a cost, or a surprise, on site.
The route through is a coordinated one. We survey the house and the rear plan, test the wrap-around against Wandsworth's planning policies and — where the address falls within one — the conservation-area appraisal, and develop a kitchen-diner that a case officer can support on daylight, roof form and materials. Once the planning principle is settled we produce the building regulations package: the structural coordination, the drainage and extract runs, the insulation and the glazing details for construction. The aim is a kitchen extension that reads as a single bright room open to the garden, rather than the narrow, cellular rear kitchen the terrace started with, and that stands up to both the planning and the technical scrutiny it will meet.
