What clearances do I need round my sink and hob?

One of the beauties of granite and quartz worktops is that it is possible to fit an under-mounted sink with a polished cut-out in the stone. Sometimes two sinks are fitted with a narrow strip of granite or quartz separating them. Any kind of undermounted installation with a polished cut-out is simply impossible with laminate worktops.

Obviously, wherever the stone is cut into, there will be some weakening, and customers need to be aware of the minimum clearances required to achieve a stable and safe installation.

The following information is given in our guide for Customers and Kitchen Installers – available, free of charge, along with other Guides and Fact Sheets from us at AG – just email us at sales@affordablegranite.co.uk

Under-mounted sinks

The key dimensions:

  • To maintain the strength around a sink cut out, we recommend a minimum of 90mm of granite AT BOTH FRONT AND BACK OF THE CUTOUT.
  • If there is a tap hole to cut into the back section of the granite we recommend a minimum of 125mm at the back.

For example: if the finished depth of the worktops is going to be 615mm with the tap to go in the centre behind, then the sink cutout can only be 400mm from front to back. (a 410mm bowl depth with 5mm overhang of granite all round is fine). If the sink is too large we may have to increase the overhang or put the tap at an angle to the side of the sink.

  • Where two separate under-mounted sinks are to be fitted side by side, we look for a minimum of 70mm on the central stone strip.

Please note that granite up-stands/splash-back may also prevent a tap position centrally behind the sink. This is especially relevant with taps where the levers move back behind the tap-hole – in some cases an installation too tight up against an upstand can prevent the tap being fully turned on!

If the sink is too large we may be forced to have a larger overhang into the bowl or locate the tap off to the side of the sink at an angle.

Sit-On sinks

The key dimensions:

  • To maintain the strength around a sit on sink cut out we need a minimum of 50mm of stone to the front AND to the rear of the actual hole.

In certain circumstances it may be best structurally to use separate slips of granite (sometimes referred to as bars of granite) to the front and rear of the sink. Where a join is required anyway to form a long run such a cut-out may be the best location for it – it avoids having a big join right across the surface. The sink looks as if it is mounted in its own section of worktop.


Most hobs are designed to drop into the kitchen worktop like a sit-on sink.

  • As with a sit-on sink we require a minimum of 50mm to the front and rear of the hob.

The same points regarding slips on sinks apply: if the hob cutout is large then the slab can be weakened and joins may be needed. This applies always if the overall slab length exceeds the maximum available. In these cases it is vastly better to avoid having a join right across the surface where bars/slips at the hob can be used.