How to Secure an Undermount Kitchen Sink | Ask This Old House

How to Secure an Undermount Kitchen Sink | Ask This Old House



then you got a stainless-steel under-counter mouth sink oh I think I see what the issue is though look at this gap right here is that it that's it all right so when this was first installed ten years ago it was pretty straightforward the countertop would have been inverted at the countertop shop or here and that sink would have been mounted that would have been caulking and a series of clips would have been drilled to make that sink attach type looks like those clips of either fail to come loose so now it is not that easy to repair this without pulling the countertop but we're going to try let me go to the truck and see if I can find these clips you ready to get under there I'm ready okay all right then I have spent a little time under here look at this here's one of the clips right here at stainless steel is a wing nut right here and look at how loose it is it's completely loose writing it so it's not holding up tight and this is actually the best one you've got right behind it look that one's gone completely over here looks like the faucet has leaked and this clip is completely rotted away see it and the one in the back is much better so really one out of four those do anything so it's hanging on by a thread what I want to do is I want to get the weight off of the sink and that means I'm going to disconnect this disposer and break these plumbing connections that we can try to drop the sink okay okay this should drop right down okay okay so all of our clips are loose let's see if it drops now okay they're good okay now what are our chances of getting this thing out of here Hey look at that a little aptitude test yeah worked all right good just set that aside now we want to clean up this surface down here we're gonna have to clean up that sink too all right all that caulking is gone thank you very much thank you all right so now we got to think about reattaching the sink and I was able to find new clips to replace those rotted ones looking how bad they were and here was the screws that are also rotted now what's really important is the way that a sink is attached into granite you know you don't want to have a hole drilled and try to use a conventional concrete screw or a wood screw any screw that as you tighten it it gets fatter and fatter because you can actually put force inside the grant and split the granite like the old feathers and wedges okay so what they've got is these little brass in sets you can see they're threaded and these are already up inside the granite right now and because they're breasts they're still good so we can reuse them okay but I was able to find the matching machine screw and wing nut right here we'll put a washer on we're in business great you let me put my thumb on the bracket so it takes a weight off it no no we're going to do is catch them loose okay this one okay is too okay all of our clips are just set loosely in place once you grab the sink and drop it back into place okay we'll get it down through the opening okay there you go thank you it came out it has to go back in right that's right hopefully okay so now just let it come down I'm gonna hold it down below okay now there's a tube of caulking somewhere right around there you see it yep it's all set to go why don't you take it and put a bead of caulking around the center of the rim of the sink all the way around you you good yep alright alright so now if you're set I'm going to push this up and you'll notice I have a little string tied into the drain do you see it I do I just pull it up yet let's pull it up and you're gonna happen that you can put your other hand and the other drain where the disposer goes okay you like that yeah I think that that's good okay so now you hold that up I'm gonna make some of these clips up okay holding now the caulking is going to take a couple of hours to cure so to add a little additional upward pressure I've got a couple of pieces of blocking to hold that sink up tight to the bottom now while the caulking is wet use your clean finger and just let's smooth it around to make a nice clean edge under the granite add more caulking if you need it now we just need to reconnect the drain lines and reinstall the disposer I tell you did a great job on the caulking looks great cleaned up perfect and the sinks upward should be so that's good now I'd like you to leave that blocking in for another day or so right let that stuff really cure and maybe not use the sink tonight take your wife out dinner actually love that okay you you

23 thoughts on “How to Secure an Undermount Kitchen Sink | Ask This Old House

  1. All my build has plywood on top of the vanity then the sink then granite. This doesnt look like it has plywood on top

  2. Those anchors will not last due to the granite deterioration. We use a much stronger method now with ez sink clips

  3. I have a small quartz bathroom sink that needs holes drilled on the underside of the quartz for the epoxied male part that receives the clip screw. Can I DIY these holes or is it risky? Instead, can I just use silicone without the clips?

  4. Here in india we all have undermount sink. Its fitted totally differntly. First its a cheap stone on which the sink is fitted over it we fit granite…. Hard 2 explain my English is bad

  5. Mark my words: undermount sink is a disaster waiting to happen.
    No matter how hard you try to do everything properly (properly clean residual dirt off both surfaces, rub with alcohol etc before reattaching unlike in the video) in 8-12 years you probably will need to re-attach it again. Several clips and silicone/epoxy aren't going to hold it forever because of thing called gravity 🙂
    If you end up using the sink, bunch of plates, several pans and pot you fill with water to let it sit and soak before scrubbing … this easily adds up to 15-25 lbs of weight. 12 inch cast iron frying pan alone weighs 8 lbs!!!

  6. Undermount sinks usually come with a set of support brackets, screws and insert anchors. You mentioned that your anchors were "already in" your countertop—but you've actually EXPOXIED them into the countertop, right? That's how it looks, anyway, and how I'd do it.

  7. and this is why I HATE undermount sinks…..I have the same exact problem right now….I despise these kinds of sinks. Mine was installed way worse than this one. I had ZERO clips on mine.

  8. There are many ways to mount an undermount sink, and you'll be amazed by all the different methods stone fabricators around the world use. Nothing works 100% of the time and each different situation may require a different thought process. If you want mechanical support, please check out products made by Sinkits Mounting Solutions. We've sold millions of products to stone fabricators all over the world who do this work on a daily basis. Most of them are much easier to install then this.

  9. Those brass inserts are not that strong. What keeps them attached to the granite? Epoxy? How many are there? Four? Why? Are these expensive? Imagine the sink full of frying pans ad topped up with water, how heavy is it? Then the garbage disposal adds vibration (this may be the killer) to the whole kit and caboodle. Do the math, or do a pull-out test with a force gauge.
    Silicone RTV is strong, but bonding to granite, likely very porous, is not that good, and vibration and heavy static loading will make it weak.
    Maybe 10 or 20 clips may be enough, or some other means of support, that can take the vibration and static loading.

  10. Check out ez sink bracket. It can be a DIY. If you want to do it right however. You will need to pull all silicone off, clean and reapply silicone for a tight water proof seal. The bracket itself is an easy install. 10 Years in owning a granite fabrication company.

  11. I did an under mount 12 years ago that will never fail on a kitchen in a house I renovated to live in. I matched the cabinet width to the sink and the lip rests on the cabinet. Then added front and back support under those lips.
    Now I am doing new house with a concrete cabinet with a thin steel reinforced slab beneath the counter. The sink hole opening will match the sink lip all the way around. The sink will be flush with the concrete support slab. The granite top will rest solid on the slab with full support. Why take chances when the solution is easy to see?

  12. I did an under mount 12 years ago that will never fail on a kitchen in a house I renovated to live in. I matched the cabinet width to the sink and the lip rests on the cabinet. Then added front and back support under those lips.
    Now I am doing new house with a concrete cabinet with a thin steel reinforced slab beneath the counter. The sink hole opening will match the sink lip all the way around. The sink will be flush with the concrete support slab. The granite top will rest solid on the slab with full support. Why take chances when the solution is easy to see?

  13. Use a Hercules Universal Sink Harness or a Sink Strap. I fix these in an hour and a quarter tops, and never have had a callback.

  14. I have easier and cheaper route that works better. Cut 6 1×2's that fit snug from the bottom of the cabinet to the flange part of the sink. Place one on each corner, one in the middle behind the piece of wood located in between the two cabinet doors and one in the middle on the back side of the cabinet. Silicone the lip and put sink into place and add the 1×2's, simple and cost about $3.

  15. Poor installation. If it was not installed right, re-install it RIGHT with Pete's Sink Mount kit. I guarantee this mounting kit will work perfectly and you can even install it in situations like this! Support the sink properly but "cradling" if from the bottom, not trying to hold the rim with some little clips screwed into the granite. The sealant is NOT designed to "glue" the sink to the granite, it will fail just like it did the first time. That is a horrible way to secure a sink to granite. Granite is brittle and not designed to screw things into it. BAD idea. It will fail again. It is sad how nobody does things properly any more. Check out SinkMount . com and see how to do it right and last a lifetime. Thank you!

  16. @This Old House: I have a far easier way that i used to do when fitting granite counter tops. Grab a silicone tube of C-TEC CT1. Push down the sink and remove all the old sealant from the rim. Cut 3 pieces of 2 x 4 (if you have a 2 hole sink). 1 Piece will need to be 2 inches larger then the widest dimension of the sink. The other pieces need to be 2 inches larger then the sink drainage hole. Grab some cable ties and tie 2 pairs of 3 cable ties into a loop. Run a gasket of CT1 around the center of the rim on the kitchen sink and pull it directly up onto the stone and center it with a tape. Place the small timbers under the sink drainage holes and loop the cable ties around them up through the drain holes. At the top run the large 2 x 4 through the loop and pull the cable ties as tight as you can get them. Finally crawl under the sink and twist the small 2 x 4's 360 degrees to tighten the fixture fully. Wait 24 hours and cut the cable ties. It will hold rock solid forever. No faffing around with clips or glueing support pieces or propping up the sink with a piece of wood.

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