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What clearances do I need around my sink and hob cutouts?

What are cutouts?
kashmir gold granite undermount sink in Horsham west sussex polished cutout cutouts

A kitchen needs a place to cook and a place to wash, rinse, drain and supply water. Cooking needs either a free-standing cooker or a hob built into the work surface. Sinks and hobs need holes to be cut in the worktop, and we call these cutouts.

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 twin cutouts and a narrow strip of stone separating them. Any kind of undermounted installation with a polished cut-out is simply impossible with laminate worktops. See our companion article on different types of sink.

Hobs sit on top of the work surface, with a flange covering the cutout beneath. For hobs and sit-on sinks, unpolished cutouts are needed.

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

We work these days in granite and quartz, with considerable variation from one material to another in terms of tensile or flexural strength. We also frequently work in 20mm quartz. The minimum clearances given are based on the use of any 30mm granite or 20mm quartz. Larger clearances may be needed in some quartzite-type natural stones, and narrower ones can be handled in 30mm quartz. Please call us to discuss, if in any doubt.

granite quartz reflection polish staining worktops red
Under-mounted sink cutouts

The key dimensions:

  • To maintain the strength around a sink cut out, we recommend a minimum of 90mm of granite AT FRONT, BACK AND SIDES 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.

polished sink cutouts Eternal Pearl Jasmine sink 2
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  • 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 impede a tap from being positioned centrally behind a sink. This is especially relevant with taps where the levers move backwards – in some cases an installation too tight up against an upstand can prevent the tap being turned on! Please see our separate article covering rear-swing lever taps.

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.

Some sink manufacturers sell sinks that are described as being suitable for either under- or top-mount use. These are generally not the ideal choice as they often have a deeper flange that is not as aesthetically pleasing when fitted, and often leave little room for the tap hole. We would also NOT recommend stainless steel under-mounted sinks which have a tap-hole cut into the sink (i.e. where the tap is attached directly to the sink and does not require a hole cut into the stone). If you have any concerns about your sink, please contact our sales team to discuss its individual suitability for your particular installation.

Belfast/Butler sink cutouts
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With Belfast/Butler sinks it is important to ensure that the tap(s) can be plumbed-in after the worktops are fitted. One way to facilitate this is to cut the hole for the waste in the supporting shelf as a slot, open towards the front of the cabinet. In that way the sink can be slid forward under the stone to improve access. We normally recommend the Belfast sink is pulled forward so that the front sits approximately 20mm past the door fronts. This will be in line with the finished worktop, allowing room for the taps behind.

Sit-On sink cutouts

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, REAR AND SIDES of the actual hole, and more in weaker stones.

In certain circumstances it may be best structurally to use separate slips of stone 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.

cutout clearances silestone crema urban quartz workrtops topmounted sink unpolished cutout
Hob cutouts
cimstone arcadia white quartz worktops hob cutouts with bars crawley west sussex

Most hobs are designed to drop into unpolished cutouts in the kitchen worktop just as a sit-on sink does.

The key dimensions:

  • As with a sit-on sink we require a minimum of 50mm to the front, rear and sides of the hob. For gas hobs, the 50mm minimum is measured up to any upstand. Please note that further clearances may be required by the hob manufacturer and Fire Regulations; our clearance guidance has to do with the strength of the stone we install.

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 much better to avoid having a join right across the surface, and so small joins and bars/slips at the hob can be used.

Other clearance issues

The other issue of clearance that can become critical is in the vertical dimension. Contemporary kitchen styles cry out for thinner profile worktops. We often fit 20mm thick quartz. Please see our article on thinner worktops, which tackles some of the challenges of the slimline look.

silestone blanco city 20mm cutouts ashford_middlesex_132344_a_hob_splashback-min

We are Affordable Granite, the leading installer of granite and quartz bespoke kitchen worktops in Surrey, Sussex and across the South East. For samples, quotes and any questions connected with any aspect of worktop installation or kitchen design, please don’t hesitate to contact us on 01293 863992 or by email on sales@affordablegranite.co.uk