Will the slab fit up the stairs? The four measurements that decide, and when a join stops being optional

01 / 07

The short answer

Nothing in law governs this. There is no regulation about carrying worktops up staircases, and anyone who tells you otherwise is dressing a trade judgement in borrowed authority. It is geometry and weight, and both are measurable before anybody commits to anything. Access is the first of the London constraints most people run into, and the only one that changes the product rather than the date.

02 / 07

What a piece actually weighs, with the working shown

Start with a number you can check. Caesarstone publishes the weight of its own material by thickness: 66 to 70kg per square metre at 30mm, 43 to 48kg at 20mm, and 29 to 33kg at 13mm. Multiply by the area of the piece and you have its weight, give or take the cut-outs. A three-metre run at 620mm deep is 1.86m², so at 30mm it is somewhere between 123 and 130kg. The same run in 20mm is 80 to 89kg. That difference of forty-odd kilos is the single strongest argument for 20mm in a flat with an awkward stair, and it is a conversation worth having before you fall in love with a chunky edge.

Now put that against what a person can handle. The Health and Safety Executive’s simple filter for one person lifting a compact load close to the body tops out at 25kg, and the HSE is careful to say that the Manual Handling Operations Regulations 1992 set no specific weight limits and that the filter values are not safe limits. The Regulations themselves require an employer to avoid handling that risks injury where reasonably practicable, and to assess and reduce the risk where it is not. Team handling always needs a fuller assessment than the filter provides, which is the formal way of saying what every fitter knows: a load shared between four people is not four times a one-person load, because the four of you cannot all get a hand on it on a staircase.

Our working rule, and it is ours rather than anyone’s law: two people carry a piece up to roughly 90kg on a straight flight. Above that it is three. Anything over about 150kg, or anything that has to be turned at a half-landing, is four, and at that point the limiting factor stops being the weight and becomes whether four people can physically stand around the piece in the space available. That last sentence is the whole article in miniature. Stone is not too heavy for a London stair. A London stair is often too narrow to put enough people on it.

03 / 07

The four measurements

A survey takes about fifteen minutes and needs a tape, not a laser. These are the four numbers, in the order they are taken, and the reason each one matters.

• Stair width at its narrowest point, measured from the wall to the inside face of the handrail rather than to the far wall. The handrail is what your knuckles hit. Approved Document K sets no minimum width for a stair inside a dwelling at all (the 1200mm figure people quote applies to buildings other than dwellings) which is exactly why a Victorian terrace can legitimately have a stair barely wider than a person.
• The pinch point at the half-landing newel. This is the one that fails jobs. On a quarter- or half-turn, the piece has to rotate about its own centre, and the newel post is a fixed obstruction at precisely the height where the carriers’ hands are. Measure from the newel to the outer wall, not from the tread.
• The diagonal of every door frame on the route, not the width. A piece goes through a doorway on the skew, so the governing dimension is the frame’s diagonal minus the thickness of the stone and the fingers holding it.
• Headroom over the turn. Approved Document K asks for at least 2m of clear headroom on access between levels, so in a compliant modern stair this is rarely the binding constraint. In a converted loft stair or a basement flight in a period house, it very often is, because those predate the guidance entirely.

Two things sit outside the tape measure and are worth settling in the same conversation. The van has to stand somewhere legal for most of the working day, so in a controlled parking zone somebody needs to suspend a bay, and that has a published lead time of its own. And the carry has to happen inside the borough’s permitted hours for noisy works, because a piece being manoeuvred up a common stair at seven in the morning is not a quiet operation.

04 / 07

The point where carrying stops and jointing starts

Slabs are finite to begin with. Caesarstone publishes a nominal standard slab at 1440 by 3050mm and a jumbo at 1640 by 3270mm; other makers publish their own, and once your runs are nested with cut-outs allowed for, the longest usable piece is shorter than the raw dimension suggests. So some kitchens were always going to have a join. The access question is whether you get more joins than the slab alone would have imposed.

The threshold is not a single number, because it is the interaction of four. In practice: a straight flight with a door at the bottom will usually take a piece up to about 2.7 to 3 metres, which covers most kitchen runs. A half-landing turn typically caps a piece nearer 2.2 to 2.4 metres, because the piece has to rotate in the space between the newel and the outer wall. Below about 2 metres, almost anything is possible. Those are working figures from carrying stone up London stairs, not published standards, and the survey exists precisely because your stair may not behave like the average one. A common stair in a right-to-buy flat, with a concrete half-landing and a solid newel, behaves differently again from a domestic stair inside a house.

“I would worry less about the mass and more about whether they can get significant lengths of it up the stairs.”

A homeowner answering the same question, Mumsnet property board, January 2024

That poster had it exactly right, and it is the reverse of what most people worry about. Nobody rings us frightened of a join. They ring frightened that the floor will not hold it or that the stone will snap. Neither is the real risk. The real risk is that a run you wanted in one piece becomes two, and that nobody tells you until fitting day.

05 / 07

An access joint is a decision your building made. Place it anyway.

Here is the part almost nobody writes down. When access forces an extra join, two things are true at once. The first is that you did not choose it, the stair chose it, and no amount of paying more will move a newel post. The second is that where it goes is still entirely a choice, and it is yours as much as ours.

A join that lands wherever the nesting software put it is a defect of process, not of the building. A join that lands over a cabinet gable, clear of the sink and hob cut-outs, and out of the sightline from the door you walk through every morning, is invisible in most consistent quartz and forgivable in a veined granite. Same job, same constraint, entirely different kitchen to live with. Our companion guide on where worktop joins go decides this question on design grounds, runs, corners, sinks, sightlines. This page decides it on access grounds. When the two disagree, access wins on the fact that a join is needed, and design should still win on where it goes.

• Ask, at survey, how many pieces your kitchen will arrive in and why. "Two, because the stair caps a piece at 2.3m" is an answer. "We will see on the day" is not.
• Ask to see the join positions marked on the plan before fabrication starts, not before fitting.
• If a run is only slightly over the access limit, ask whether shortening a return leg by 100mm would bring it under. Sometimes it does, and it costs nothing but a conversation.
• If you are choosing thickness anyway, understand that 20mm is roughly a third lighter than 30mm for the same piece, which occasionally converts a two-piece run into a one-piece run.

06 / 07

When the stairs are genuinely not the route

Occasionally the honest answer is that the piece is not going up that staircase in any configuration that leaves you with a kitchen you would want. There are three remaining options and one of them is usually right.

07 / 07

Questions people actually ask