Can you change a top mount sink to under mount in granite?

When you purchase a new house the builder often includes a free upgrade to granite for free, and it’s great because it’s something that you don’t have to upgrade later.  The problem is, many people prefer an under mount sink to a top mount sink and don’t really think about it until after they move into their home.  Some builders may only upgrade the countertops to granite but not the sink to an under mount sink.  So if you are stuck in this scenario, what are your options?  Is it possible to swap the top mount sink for an under mount one?

Supreme 1.5 elipso cropped

To adequately answer this question, you need to understand how the sinks are cut out for top and under mount sinks.

Top mount sink cutouts: this can be done in the countertop fabrication shop or on location, at the home.  The cut out does not have to be precise as the opening is covered by the ledge of the sink.

Under mount sink cutouts:  The sink must be cut out in the fabrication shop on a CNC machine and water polished.  The opening must be cut to the exact dimensions of the sink since any errors would be very noticeable.  Often times the fabricator will want to have the sink (or at the very least, the .dxf file of the cut out from the sink manufacturer) to cut the opening properly.

So is it possible to take a granite countertop with a top mount sink and switch for an under mount sink?

Well, you definitely can’t do it on site.  Even a countertop service technician with the steadiest hand can’t cut granite the way it needs to be cut to fit an under mount sink properly and the edge of the cutout would have to be water polished and would cause a lot of water damage.

If we can’t do it in home, can we remove the countertop, bring it to the shop for the CNC to cut it and have it water polished?

Whenever you are removing installed granite countertops, you risk the granite breaking. And if there are seams in the countertop, that can increase the risk of the countertop breaking.  If a section of your granite breaks, you will have to replace all the countertops in your kitchen.  All granite slabs, being a natural stone, are different and unique.  Even if the colour name is the same, the granite can look very different.  So if you have Giallo Veneziano granite in your kitchen and you need to replace a section of your countertop, you may not be able to match it up.

Giallo Veneziano

Cost will also be a factor if you try this route.  You would have to pay for the company to uninstall the countertop, bring it back to the shop, put the top on the CNC machine to get cut, bring it back to your house and reinstall it, without a guarantee that the granite wouldn’t break during uninstallation, en route, or when they are trying to recut the new sink opening.

For these reasons, many countertop fabricators do not perform this service.  So what are your options now? You hate the look of your current top mount sink but an under mount sink is out of the question and you want to keep your current granite for now.

Sink manufacturers have made top mount sinks more attractive, more like a flush mount sink so the look is very clean.  BLANCO has their MicroEdge® series.


All you have to do is pick a sink that will fit in your existing sink opening.  Need a bigger sink opening?  You can get it cut larger by your local countertop fabricator’s onsite service technician.

Hope this helps!

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