Can an Existing Granite Countertop Sink Opening be Enlarged (in Place) to Put in a Slightly Larger Undermount Sink?
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Question by S2art: I have a granite counter top with a double under mount sink already installed, but I would to replace it with a slightly larger single bowl sink. Do granite dealers have the capacity to wet cut the larger opening on site in my kitchen? Otherwise, I presume once one has a granite counter top, the sink can not be changed out for something larger or different in shape.
Answered by LCD: The poor countertop contractor who gets you job will swear at me, but yes - it is possible, though I would bet pretty much every bidder will want to take it out to their shop to recut it - which might be cheaper in the long run. It take very meticulous cutting and routing if done with hand tools rather than a shop milling machine - and being a very hard stone, takes diamond blades and slow work, or one of the new very expensive portable laser stone cutters.
Whether the existing countertop can take a larger sink depends on its existing free edge dismension front and back and also where the exit pipe from the trap into the wall is, and on whether it was reinforced under the narrow front and edge strips when it was installed. I always full-contact glue a reinforcing piece of plywood underneath under the narrow strips and all around the sink cutout edges but many installers do not, so that can severely limit how far you can cut into it for a larger sink. And of course, if the new sink is going to extend beyond the inner edges of the sides of the cabinet, that is hard to do from underneath too, though doable.
When talking to installers about bids, I see no reason to demand it be done in-place - just let them bid it either in-place or removal and shop cutting and reinstallation, whichever they are most comfortable with. I have done a lot of in-place modifications of countertops but I also know of some contractors who will not touch that and always remove them and take them back to the shop to work on.
Cost depends totally on your configuration and granite thickness (which can vary from 3/8" to 4 inch in different kitchens) and access, but I be would be very surprised if the old sink removal, cutout cost and new sink install were less than $400 and possibly much more - plus the cost of the sink, and maybe $200-300 or so plumber cost depending on plumbing mods needed to configure piping to the new sink.
Here is a related prior question with answers on a similar line that might be of interest to you too -
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