New hob does not fit the old cutout: what actually needs to change

The old hob is out, the new one arrives, and it either drops through the hole or sits an inch proud. Cutout dimensions vary between brands and even between models, and the counter was cut for the one that was there.

Measure before you buy

Take the length and width of the existing cutout, not the old hob's outer size. Every hob's manual lists the cutout it needs. Match it, or plan to change the counter.

Too small: the hole

A carpenter can enlarge a cutout in a wooden or laminate counter. Stone and quartz need a fabricator with the right blade, and there is a limit to how close you can go to the edge before the counter weakens.

Too big: the hole

Harder. A hob needs the counter to bear on its rim all round. A trim ring can cover a small gap; a large one means a filler piece or a new counter section.

The clearances that matter

• Distance from the hob edge to the wall behind — the manual specifies it
• Height of the chimney above the hob — typically 65 to 75 cm for gas
• Depth below the hob for the valves and gas connection — a drawer directly underneath usually has to go
• Nothing combustible within the stated margin on either side

A hob forced into a cutout that is slightly small, with the rim not bearing evenly, will crack its glass under the first heavy pan. Get the hole right, then fit the hob.

Who does what

The counter change is carpentry or stonework. The hob fitting, gas connection and leak test are the technician's. Book them in that order.