How to repair a 'falling' undermount sink?

osxaddictDecember 13, 2007

Hi all.. We've got an older under mount sink that was installed more than 17 years ago and the glue/sealant that was used to attach it to the granite counter top has failed on the right edge. There don't appear to be any clips on the bottom of the sink to attach it to the granite. At this point, if you splash water on the top-right edge of the sink, it runs down into the cabinet.. Aside from removing (and destroying) the granite, what's the best way to reattach the sink to the granite? I can probably clean some of the crap off that was originally used to hold the sink and replace with something, but I'm not sure what. Luckily the sink can't drop as its still got the plywood to catch it -- the gap in place now is probably a 1/16" or two.. Any ideas? Is this a common problem?


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Our granite installer used Bondo a week and a half ago. I've also heard they use it to attach the granite to the counters. Easy to get and work with.

    Bookmark   December 14, 2007 at 1:50AM
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Sounds to me (if I am understanding you right) that your
sink is sandwiched in between the underside of the stone
and the plywood subtop.. I'm going to presume that's the case,
and IF it is...
this sounds like a simple case of
the seal between the sink and the stone has been compromised....

All that's really needed is that you'll need to scrape
out the old caulking, and re-apply some new caulk.

here's a few pics to illustrate what I am under the impression
of how your sink is installed:

5/8" plywood subtop, screwed down to cab has adhesive applied

sink opening is cut ou in plywood subtop

sink is set in place - set on a bead of caulk..

sink is now in final position

note the space cut out in back to keep the plumber happy

another bead of caulk (silicone) is applied to the top of sink flange....

sink & subtop are ready for Granite countertop to be set

finished assembly prior to caulk being cleaned & tooled

same kitchen - main sink opening in subtop

sink being set in place

sink in final position

scutcheon opening in back to keep plumber from "crabbin"

IF this is how your sink was installed, it's really important
that you get that gap that's allowing water to leak into
your cabinets... FIXED...PRONTO!!!

The water will affect the plywood subtop (I'm presuming
that you have plywood and NOT OXB, Flake/Particle Board
or Masonite -ALL of which (IMHO) are CA-CA for use
as subtops - IF water gets into any of them, they'll
swell up like a watermellon and fracture the stone
that's set on them) - so get that seal RE-CAULKED!!!


Hope the pics help


Kevin M. Padden MIA SFA
Fabriactor, Trainer & Consultant to the Natural Stone Industry

Here is a link that might be useful: AZ School of Rock

    Bookmark   December 14, 2007 at 7:52AM
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Try Chemical Concepts by Braxton Bragg. They make a peel and stick fastener for a sink that was installed without clips. I'm using some myself. Call them and ask for the peel and stick ones.

Here is a link that might be useful: Chemical Concepts

    Bookmark   December 14, 2007 at 3:16PM
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