Hey Everyone got a question
I have an undermount sink in a new kitchen the countertop is granite and the sink is stainless. It was installed by a so called “professional” the only problem is I have been waiting three months for him to come back and all I get is excuses. I am very handy and looking for a little inside information. The sink keeps pulling away from the granite when it was installed he used a flush mounted bolt that was epoxied to the bottom of the granite and they keep popping off. Know to me it seems that a small hole drilled maybe a 1/4 to 3/8’s of an inch in and then an epoxied stud would hold a lot better. But Iam afraid to drill the granite and end up with even a bigger problem like cracks or chips. Is there a special bit that I can buy and I would imagine I would have to drill it real slow. Or am I better off with a flush mounted type fastener and epoxy and if so can anyone recommend an epoxy that will handle the job. By the way it’s a double bowl sink that is 17x30x8″ under a 1 1/4″ piece of granite.
Thank you for any help.
John
Edited 9/27/2004 1:56 pm ET by john7109
Replies
Me, I'm a wood guy, so I'd stay away from drilling granite. I'd use wood to build a bridge underneath the sink flange. The bridge would be fastened to the sides of the sink cabinet. If I had enough room to insert them, I'd put shims on top of the bridge to support the sink. If I didn't have enough room to insert the shims, I'd put a couple of screws through the bridge, and have their tips push up on the sink.
This approach is based on the way I've done kitchens with stone slab counters. I cover the lowers with plywood, and mount the sink to the plywood. (I rout the top surface of the ply so the sink flange is flush.) The granite guy puts the slab on top of the plywood. There's no mechanical connection between the slab and the granite.
The clear silicone caulk used to bond the sink to the bottom of the top is plenty strong enough to hold the sink in place without the anchors. You need to remove the sink, clean thoroughly any remaining adhesive and then reinstall with a heavy bead of silicone. If you can use the existing anchors or put new anchors in the existing holes, this will help. If you cannot, then it is not that big of a deal. The sink will need to be supported with blocking until the silicone cures.
carpenter in transition
small Tapcon screws and washers might work. Look on page 164 of the book "Concrete Countertops" by Fu-Tung Cheng. They sell the book at Home Depot. I would call some granite suppliers and see if its ok to drill.
If so then this is the way I would do it.
Im going to build concrete countertops soon.
I would never use a Tapcon in granite.
Jon Blakemore
get a wood support system or a two part epoxy or something other than that hammer drill ---that close to an edge and you could wind up epoxing more than just the sink....If the sink is that loose -pry it off clean it and use silicon with some temp. legs and once it is set give the support system a go. It will all be against the back and under the tops so you are not going to lose any cab. space.. Hope it all works out. Mike
Ours was installed with silicone only and we haven't had a problem in 6 years now. I wasn't there when it was done (might explain why it hasn't failed!)
I just had a look at ours. There is what appears to be two sheets of 1/4" or 3/8" ply sitting on top of the open cabinet tops with a cut out for the sink such that the sink flange is supported by the ply.
Edited 9/30/2004 4:10 am ET by e2canoe
I know it sounds hard to believe that you don't need those fasteners,but
if you don't trust me, silicone a scrap of bent sheet metal to the back side of a granite top. Let it cure, and then try to rip it off. Superman couldn't even do it on a good day. I've tried it. And I have stood inside a stainless bowl hung from a granite top. Jumped up and down a few times.
Redrilling a top in place is a dangerous waste of time.
Tapcons rely on the surrounding substrate to have some level of give. That is why they work better in concrete block than in poured concrete. Granite will shatter if you try to install a tapcon into it.
carpenter in transition