The first useful question about a Tufnell Park kitchen is not how big it can be but what level it is on. These are unusually generous Victorian houses — tall terraces and semi-detached villas built for the comfortable middle classes, set behind leafy front gardens on streets that climb towards Dartmouth Park Hill — and a great many of them carry a garden or lower-ground storey where the original kitchen was put. That kitchen is typically half a storey below the street, reached by an internal stair, and it is sometimes not level with the garden either. So the design begins with a measured section rather than a plan: existing floor level, existing garden level, the height of the ceiling above, and the vertical gap between the two that everything else has to resolve. Two houses on the same street can give completely different answers, which is why we level the rear of the building before we draw anything.
Once that gap is measured, there are only three honest responses to it, and choosing between them shapes the whole project. You can accept the level and step out to the garden, which is the cheapest and least contentious route but leaves you with a threshold and a flight of steps at exactly the point where you wanted a seamless connection. You can lower the internal floor to bring the kitchen down towards the garden, which buys head height and a level threshold but turns the job into an excavation. Or you can raise and terrace part of the garden to come up to meet the house, which sounds simple but usually means new retaining structure and a smaller usable garden. Hybrids are common: dropping the floor part-way and taking up the remainder in a single generous step often gives the best room for the least disruption. We price and draw the section options early, because it is much cheaper to change your mind on paper than on site.
Lowering the slab is the option owners most often want and least often understand. Dropping a floor beneath a tall Victorian terrace means working around whatever the existing footings turn out to be — typically shallower than modern ones, though that has to be established by trial hole rather than assumed — and brickwork that is old and solid, and it usually means underpinning at least part of the party wall so the neighbouring house is supported while yours goes down. That is squarely Party Wall etc. Act 1996 territory, and it engages Islington's basement and lower-ground policy at the same moment. It also changes the building fabric problem: a floor set below external ground level has to be waterproofed as a structure, not just tanked as an afterthought, with the drainage and the maintenance of that waterproofing designed in from the start rather than added when the room is already built. None of that makes lowering the floor a bad idea — it makes it a different project, with a different programme and a different set of specialists, and it should be recognised as such before a budget is set.
The step out to the garden is a structural element in its own right. Where the ground behind the house is higher than the new kitchen floor, the rear wall of the extension and the flanking walls are doing retaining work, and any existing garden or boundary wall that was already holding ground back has to be assessed rather than assumed sound. The threshold detail is where these projects succeed or fail in use: a flush sliding door onto a stepped terrace needs a drainage channel, a fall away from the building and a robust waterproofing junction at the exact line where the retained ground meets the glazing. Getting this wrong produces a beautiful kitchen with a damp back wall, which is among the most avoidable defects in garden-level extensions, and it is usually a drawing failure rather than a workmanship one.
Daylight into a garden-level kitchen has to be won deliberately, because the room has earth or a retained wall on one side and a deep, tall house on the other. Light arrives from the garden end and from above, so the section usually wants rooflights in the new flat roof, a glazed link where the extension meets the original rear wall, or a light-well cut against the retained side. The trade is thermal: a lot of horizontal glazing over a deep plan makes an overheating problem, so the glazing area, the shading and the ventilation strategy are set together. Meanwhile Islington will be assessing the effect of your extension on the daylight reaching the neighbours' windows using the BRE tests, so height near the boundary is the variable to control. A garden-level scheme has a quiet advantage here: because the floor is already low, the roof of the extension can sit well below the neighbour's sill line.
The services follow the level, and they are the part of a garden-level kitchen that catches people out. An extract duct for a kitchen at the bottom of a five-storey house has to go somewhere, and terminating it discreetly on a rear elevation that may sit in a conservation area is a design decision, not a builder's afterthought. Waste and drainage are harder still: if the floor is lowered, the new kitchen and any new WC can end up below the invert of the existing drain, which means a pumped installation and a maintainable route out. Add the steel needed where the original rear wall is opened up to the new space, and the coordination between architect, structural engineer and drainage becomes the real work. Asking contractors to price before that detail is settled is how a Tufnell Park kitchen budget comes apart, so we resolve it in the drawings and let them price what is actually going to be built.
