A kitchen extension in Blackheath is really a ground-floor reconfiguration with a new room on the end, and the more consequential decisions are the internal ones. A Victorian or Edwardian family terrace here typically arrives with a compartmented back-of-house: a small kitchen against the rear wall, a separate dining room in front of it, and a spine wall between them carrying the floors above. Opening that up into a single kitchen-diner is what most owners actually want, so the question is not only how far the new box projects but which walls come out, where the beam that replaces them lands, and how the kitchen, table and circulation resettle across the whole ground floor. We plan the extension and the existing rooms as one exercise, because a well-built addition bolted onto an unresolved plan wastes both.
Daylight is the problem a deep kitchen-diner creates and the one it is judged on internally. Pushing the kitchen to a new rear wall lengthens the plan, and the middle of a period ground floor — the old spine-wall zone, often the darkest part of the house — can end up starved of light unless it is designed for. The tools are a considered glazing strategy to the garden, rooflights over the deepest part of the plan to bring light down where side windows cannot reach, and borrowed light through the reconfigured openings. In the conservation area those rooflights and any largely glazed rear elevation are assessed as changes to a period rear elevation, so their proportion, framing and position are drawn deliberately rather than maximised and defended afterwards.
Services are where a kitchen extension differs most from a plain rear addition, and drainage leads. Relocating the kitchen to a new rear wall means moving its waste, and a kitchen waste run needs continuous fall to a connection that can take it, so the invert levels, the gully or stack position and the new floor build-up are settled before the units are placed. On a Blackheath terrace the existing drainage often runs to the rear already, which helps, but a relocated sink, dishwasher and utility can still outrun the available fall, and where a house has been converted the stack may be shared with a flat above. Alongside the waste sit the extract route for the hob, the hot-water and heating provision, and the electrical load for a modern kitchen, all of which we route before the layout is fixed.
Then the way the new room meets the garden, which is the point of the whole project on these plots. Blackheath's period houses generally have generous gardens, and a kitchen-diner that opens onto one wants a level, or near-level, threshold out to a terrace — which sets the finished floor level of the extension against the garden and against the damp-proof course of a period house that was never built for a flush external door. A largely glazed rear elevation facing that garden then brings solar gain and summer overheating into the same conversation as winter heat loss, so the glazing specification, the extent of opening doors and the shading or orientation are considered together. An extension that is beautiful in April and unusable in July is a common and avoidable outcome.
The structure of opening up is more involved than it looks. Removing the ground-floor spine wall and forming the rear opening usually means one or more beams picking up the floors and, sometimes, a chimney breast above, designed and calculated by a structural engineer and coordinated with the extension's own roof structure. On a semi-detached house or a terrace those loads and the new foundations sit close to the party walls, so the Party Wall etc. Act 1996 is engaged and notices go to the neighbours on the affected sides before work starts. The build-up of the new ground floor — insulation, any underfloor heating, the slab and the damp-proofing tied back into the period house — has to be resolved at the same time, because it fixes the floor level that everything else, including that garden threshold, depends on.
From there the route is a coordinated one, and in a conservation area that spans two councils it starts with the paperwork the site cannot see. We survey the house and its drainage, confirm whether Greenwich or Lewisham determines the application and whether the property is individually listed, then test the reconfiguration, daylight, services and threshold against those constraints before committing a design. We prepare the planning drawings and any heritage material the authority expects, and once the principle is settled the building-regulations package covering structure, fire, insulation, ventilation, drainage and the kitchen's services. Where the plot is closely built we identify the notifiable neighbours early and coordinate a party wall surveyor. We do not promise a particular decision; we remove the reasons an officer would have to refuse one.
