I have an undermounted Kohler sink that was attached to to the bottom side of a granite counter top. It has come loose.
It is not attached by any mechanical devices, just some kind of mastic or caulk.
I am wondering what type of compound I should use to re-attach this sink.
TIA
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first question, is it a SS or cast iron sink?
Either way there needs to be another method to attach it besides just the "glue"
The "glue" should be 100% silicone, which will hold it up very well, though shouldn't be expected to do so on it's own.
For stainless steel sinks the fabricator should have included some anchors set in epoxy to screw into, the sink should have come with the proper clips to anchor it. At a min I'll use 4 clips, one in each corner, if access is available I also like one front and back in the center.
For a cast iron sink, you can either use the mounting kit Kohler sells or build your own out of wood. Since the countertops are already installed you're going to have a hell of time if it's a cast iron sink.. there are ways to retrofit some support in though.
Edited 8/14/2006 6:57 pm ET by CAGIV
We don't rely on adhesive or fasteners. Instead, we set the rim into the roughtop under the granite. I should ad that we build Euro style cabinet carcases with a plywood top that covers the entire cabinet, so the sink is actually supported by that top. For stainless or ceramic, we rabbet into the roughtop the thickness of the rim. Stainless rims are less than 1/8-inch thick, and ceramic rims vary between 5/8 and 3/4-inch thick - in the same sink! On those, we rabbet the plywood and set the rim in thinset to bring the rim's top surface in plane with the surface of the roughtop. The granite guy glues the countertop to the roughtop and the sink rim. Sometimes he uses epoxy (my preference) and sometimes construction adhesive. Test that adhesive before using, especially on light colored stone to be sure it doesn't bleed through to the surface.
Gary W
gwwoodworking.com
Both of our Granite suppliers have warned strictly against using construction adhesive with granite because of blead through, only clear silicone.
How do you mount your sinks if your using face frame cabinets with no solid top?
I rarely build face frame cabinets, so I don't have a clue.Gary W
gwwoodworking.com
<We don't rely on adhesive or fasteners. Instead, we set the rim into <the roughtop under the granite. I should ad that we build Euro style <cabinet carcases with a plywood top that covers the entire cabinet, <so the sink is actually supported by that top. That is how I have seen it done,
But how does one change the sink in 7 or 8 years when it is trashed...gotta take the whole top off so you can remove the sink , and hope you dont break the granite...
Bud
Who trashes their sink in 7 to 8 years? I suppose one could cut away the carcase top under the sink, but then the sink would still have to be broken away from the granite, since there's at least a silicone seal between it and the sink top.Gary W
gwwoodworking.com
Mako,
There really should be some sort of mechanical means of attaching your sink, not just caulking or glue.
Years ago when I worked at a University, the method of support for undermount Durcon and soapstone sinks in lab tops was by Uni-Strut, hanging by all thread from either T-nuts in the sub top, or right angle brackets through bolted to the side walls.
A few years ago, I came across an off set undermount sink bracket from sinksetter that works well. Take a look and see if this might work in your situation.
The builder is a Georgia Tech engineer so he KNOWS everything about everything....When I asked him about this, he said that is the only way his subs ever mount sinks anymore....I guess I will re-do the silicone and make some wooden posts to support the sides of the sink.
Thanks for all the good suggestions.
I'm assuming by your comment of using wood to support the sink you have a cast iron or porcelian sink?
Yes, it is a porcelain sink...rather heavy...I was somewhat dismayed to find that the builder was sure caulk would hold it up...
Silicone is a pretty strong adhesive but not that strong.
Depending on how long ago you had the sink put in I'd call the builder to have it redone.
If you're doing it yourself you will need to clean as much of the old silicone off of the sink as well as the bottom of the granite.
If you drop the disposal and drains you can run bailing wire through the drain holes, twist it around a 2x4 that runs under the sink bowls, then do the same top side with a 2x4 running over the opening, you can twist the wire to get it tight and hold the sink where you want it while the glue sets up.
After you have the new silicone around the sink and it's held back in place by the 2x4's and wire and if you have access from cabinets on either side of the sink base I'd temp screw a 2x4 to the side walls of the sink base under the sink. Then use 1/4" carriage bolts to bolt the 2x4 to the side of sink base.
Thanks a lot for the info....I will be doing it myself, it has been in 3 years and the builder finally just wrote us a check to get himself removed from this house at the end of the first year.
This guy is unreal and contributes to giving builders a bad name. Also, I am not a nit picker. I am an old farm boy and recognize that defects in construction projects are part of the deal, having built my share of sheds etc.
The next house I build, I will be totally on top of all this stuff.
Thanks again
If you have any more questions or run into any problems along the way feel free to ask.
Good luck.
One other thing to consider: new silicone doesn't like to stick to old silicone. While there may be something else, MEK is the only thing I've used that really gets silicone off. It's bad stuff out in the open, be even badder under a sink, so take care.The plumber I work with uses a method similar to that cag suggested, but he uses bungee cords or racheting tie-downs instead of wire. I need a dump truck, baby, to unload my head
sweet idea..
I'm thinking 2x4's with eye bolts lagged in, then shorten up some of those cheapie ratchet straps...
Much easier to deal with a ledger for the sink to sit on before the tops go in though.
I want to hire your plumber... ours won't set the undermount sinks, always has the countertop guys do it before he gets there...