Setting Out a Kitchen: Clearances, Runs and Services

A hood is a length before it is an airflow

Capture is geometry. Hot air off a pan rises as a plume that widens as it goes, so a hood narrower than the appliance beneath it is being asked to catch something that has already spread past its edges, and every millimetre of extra mounting height widens the plume further before it arrives. The two dimensions fixed at set-out — the hood's length and its height above the hob — do more for the room than the fan curve does. Make the hood at least as long as the cooking surface, overhang it if the wall units allow, and take the mounting height from the instructions rather than from the eye level of the tallest person in the household. For a domestic hood the volume that matters is its own rated airflow, read against Approved Document F Volume 1 or ANSI/ASHRAE Standard 62.2, and then read again against the duct just routed.

The calculator below is not that. It applies International Mechanical Code Table 507.5, the code-minimum method for an unlisted, field-fabricated Type I commercial hood, rating exhaust per linear foot of hood by style and by the duty classification of the heaviest appliance under it. It belongs here because its governing input is a length, and that length is what you are settling with a pencil this afternoon. Run it if the range going in is a commercial or commercial-style appliance, or if the room is the back kitchen of a café rather than a house. Do not run it for an ordinary domestic hob: the answer will be large, correct for a kitchen that is not yours, and useless. NFPA 96 carries the same duty classifications, and a hood listed to UL 710 may use a lower published rate than the table.

One consequence of that table is worth carrying back into the layout even if you never run it. An island hood is rated higher per linear foot than a wall canopy of the same length and duty, because a hood standing in open air fights cross-draughts on four sides where a wall hood has one side closed for it already. Moving the hob to an island is not a neutral relocation: it extracts more air, through a longer duct, from a position with no wall to hide it in.

The front edge is a straight line because you choose it; the wall is not

Once the carcasses are levelled and pushed back, the front edge of the run is dead straight — it has to be, because doors and drawer fronts hang off it in one plane and any deviation reads as a wavy shadow line. The wall behind is whatever the bricklayer left, and in the room this page opened with it is 22 mm out of parallel with that edge. Only two places will take the difference.

You can scribe the worktop's back edge to the wall, which keeps the junction tight and takes depth out of the counter where the wall bulges. Or you can hold a constant depth, leave a gap and close it with an upstand, which keeps the counter dimension honest and moves the problem to a sealant line. On a stone or engineered top the second is usual and the first is expensive; on laminate the first is normal and belongs to the jointing guide. Either way the number you order against is set by the worst point of the wall, not by the carcass depth in the brochure.

The set-out has just fixed the splashback too. The gap between the worktop line and the underside of the wall units is a height you chose an hour ago with the laser, and if it is going up in the same material as the worktop it stops being a gap and becomes area to be bought. Counter area is therefore a function of three set-out decisions, none of them the run length alone: the length marked through the corners, the depth the worst point of the wall forces, and the splash height the wall-unit line left behind.

Two socket rules in one room, and they are not the same rule

A kitchen is the only room where the electrical layout is decided by the joinery. Every box has to land inside a wall that a carcass, a splashback or a tall unit is about to cover, and the fitter arriving after the plasterer cannot move one. So the sockets get set out with the units, on the same drawing, on the same afternoon.

Above the counter the North American rule is prescriptive and tight. Section 210.52(C) of the National Electrical Code puts a receptacle within 24 inches, measured along the wall line, of every point on the countertop, and requires one for any counter space 12 inches or wider. Section 406.5 forbids an ordinary receptacle installed face-up in a work surface, so the flush detail people ask for on islands has to be an assembly listed for countertop use rather than a socket dropped into the stone. Section 210.8 requires ground-fault protection and its scope has widened across editions, and the island and peninsula provisions in 210.52(C) have themselves changed twice recently — so confirm the edition your jurisdiction has adopted rather than the one you learned. In the United Kingdom BS 7671 sets no spacing rule at all, and the constraint that bites instead is Approved Document M in England, which holds switches and socket outlets in a new dwelling within a band measured from finished floor level.

Away from the counter the rule changes character. The dining end, the wall a bank of tall units stands against, the return by the back door: those fall under the general wall-space provision in Section 210.52(A), which requires that no point along the floor line of any wall space is more than six feet from a receptacle. Spaces narrower than two feet are exempt, and doorways and floor-length windows break a wall into separate runs. A different measurement, taken at a different height, on the parts of the room the kitchen drawing usually leaves blank.

What those outlets are allowed to share

Counting the sockets and loading the circuit are two questions, and in a dwelling two different parts of the code answer them. Section 210.11(C)(1) of the National Electrical Code requires at least two 20-ampere small-appliance branch circuits, and Section 210.52(B) then says what they must serve and what may not join them: the wall and countertop receptacles of the kitchen and the rooms grouped with it belong to those circuits. So the dining-end sockets you have just counted are usually not a separate general-purpose circuit — they are more load on the same two.

Article 220 values a general-use receptacle outlet at 180 volt-amperes, and the eighty per cent continuous-load limit applied to that value produces the familiar planning count per circuit. Be clear what that number is not. The same article puts dwelling-unit receptacle outlets inside the general lighting load rather than counting them individually, so this is a heuristic for how much you are asking of one circuit rather than the calculation a dwelling's service is sized by — and it says nothing about a kettle taking most of a twenty-amp circuit on its own. Use it to decide whether the layout wants a third circuit, then have the real calculation done against the adopted edition.

The ceiling gets set out from the units, not from the room

Downlights on the ceiling centreline put your own shadow on the chopping board. Light from a recessed fitting falls more or less straight down, the person working stands at the front edge of the counter with their back to the room, and a fitting behind them lights their shoulders. So the working line of lights sits forward of the wall, roughly over the front third of the counter, set out from the chalk line on the floor and transferred up rather than from anything about the room's own shape.

The same logic governs the rest of the ceiling plan. Pendants over an island are centred on the island, and the island's centreline is almost never the room's. Under-cabinet lighting is drawn now because its driver has to live somewhere physical — inside a wall unit, above a cornice, in the void over a tall housing — and its cable has to leave the wall at a point that ends up inside a carcass rather than three inches to the left of one. The joists overhead have already decided which of your marked positions is available, in the same void the extract duct is crossing.

Then the load, which surprises people because the fittings are individually small. A contemporary scheme adds downlights, two or three strips of under-cabinet lighting, plinth lights, an island pendant group and sometimes a lit cornice, and hangs the lot off whatever circuit already serves that floor. Count driver input wattage rather than the incandescent equivalent on the box — the second is a marketing figure, not a load — and check the total against the continuous-load limit in Sections 210.19 and 210.20 of the National Electrical Code rather than the breaker's face value.

Finished floor level is a set-out dimension, and it is the one people leave until last

One number in this room cannot come off the level line: the thickness of a floor that has not been laid. Tile plus adhesive is commonly twenty to thirty millimetres of build-up, and everything measured from finished floor upward — plinth height, the aperture the dishwasher stands in, the point at which the back door stops closing — moves by that amount after the units are levelled, unless it is built into the leg height on the day.

The second decision is extent: tile the whole footprint before the carcasses land, or tile the visible field and stop where the plinth will sit. That choice changes the area you are ordering against by the depth of the run times its length — over three square metres on a single 5.2 m run, and more again once a return is counted. The floor's own set-out — where the first full tile lands, which cut the threshold gets, how the grid meets the plinth line — belongs to the tiling guide. And a trap sits between the two decisions: lay a new covering in front of an integrated appliance whose aperture was set to the old floor and the machine never comes out for service again without the floor being cut. Five minutes with a datasheet and a tape, before the legs are wound, is the whole of the fix.

1. Write the intended build-up — covering plus bedding — on the wall in pencil before a leg is adjusted.
2. Set the leg height so the worktop lands on the level line with that build-up allowed for, then check what plinth height is left.
3. Take every integrated appliance's aperture off its own datasheet and confirm it at the worst point of the floor.
4. Decide the tiling extent before ordering, and take the area off that extent rather than off the room.
5. Check thresholds and door clearance last, with the finished level marked, while a fouling door can still be trimmed.

The chalk lines have already spent some of the money

Three of the quantities that drive a kitchen's cost have now stopped being estimates. Base run and wall run are the lengths on the floor, measured through the corners with the posts and fillers already added; worktop area is that length, the depth the wall forced, and the splash height the wall-unit line left. None of it came off a showroom plan, and it is the first honest version of those numbers anyone has had.

That makes the afternoon of the set-out the cheapest moment to test a layout change. The gangway argument usually resolves by deleting a unit — a 1000 mm base goes, the walkway gets its hundred millimetres, the run shortens. Price the two versions against each other with your own rates before agreeing to it, because the answer is sometimes that the deleted unit was the cheap way to buy the storage and the island replacing it is not. Fill the services and finishes lines with real figures from the trades who have now seen the room: everything located in the last two hours sits in those lines, and they are the half of a kitchen that cannot be changed later without taking the visible half back out.