How is an umdermount sink typically attached?

boone_2009August 8, 2013

Sigh. I thought I was done with sink questions :-(.

However, fabricator says that our ss undermount sink will be held in place by clips only; no adhesives ( quartz countertop with plywood beneath).

I was under the impression that epoxy adhesives are used in addition to clips.

Please give me your feedback. Thanks!

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oops, sorry about the typo!

    Bookmark   August 8, 2013 at 8:25PM
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Clips are fine but you'll also need a bead of silicone between the sink & the countertop.
Not for strength, but for sealing out water.

    Bookmark   August 8, 2013 at 8:44PM
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I wouldn't trust adhesives to hold a sink full of water.

As for your question - I was planning to use a Sink Setter, but now that my sink base is only 30" wide, and it's a 60/40 sink, with an offset. The Sink Setter can accommodate the offset, but not in such a small cabinet.

Templater and cabinet maker will both be here tomorrow, and I'm sure between the two of them they'll figure out how to support the sink.

    Bookmark   August 8, 2013 at 8:44PM
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Clips, silicone, and we have a wood support under the sink. Techincaly we could remove the wood if we needed to but its not in the way so we leave it.

    Bookmark   August 8, 2013 at 9:36PM
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Thanks, annkh, willtv and debrak2008.

Yes, he'll be using silicone between the sink and countertop. Clips, of course. No wood support underneath.

    Bookmark   August 9, 2013 at 2:02PM
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annkh: Could you please tell me what your fabricator and cabinet maker finally decided regarding the attachment of your undermount sink? Has it been done?

    Bookmark   August 30, 2013 at 1:28PM
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Thanks for thinking of me, boone! Our countertops go in next Wednesday (Sept 4). For a variety of reasons (vacation plus work) I won't have much chance to post until the following week.

Rest assured I will post details!

    Bookmark   August 30, 2013 at 1:55PM
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annkh, good luck with your countertops!

Our fabricator today said he will *not* be using clips to hold the sink but if we really want them he will put them in. he says that with the 3/4 inch plywood subtop, it is better to use adhesive. He said he knows what he is doing. Fingers crossed!

    Bookmark   August 30, 2013 at 4:01PM
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Adhesive alone is not enough.
You need to use clips or some other type of under sink support.
Our installer used 9" shelf brackets screwed into the cabinet walls. One on either side of the sink.
I haven't had occasion to stand in the sink, but I probably could.
Here's a shot or 2 from under the sink cab.

Right side

Left side.


    Bookmark   August 30, 2013 at 7:35PM
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clips are usually attached to the countertop with epoxy. There are different systems like this around.

    Bookmark   August 30, 2013 at 8:37PM
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willtv and weedmeister: Thank you for your replies.

If you have chanced upon my other thread regarding "flush mount vs reveal mount", you will know what a long and arduous road we have been traveling with our fabricator when it comes to sinks/cutouts.

We will have a Silestone countertop ( Lagoon).

When he came over to template ( three whole weeks ago)he clearly told me that he would not use the clips provided by our sink manufacturer ( Vigo) but would 'use other clips'.

We signed a contract last week specifying that it would only be final contingent upon his meeting all our requests - and we mentioned every one clearly.

One of our requests was worded thus::
"Clips and adhesives to be used for attaching undermount sink ( Murofix adhesive is recommended in the Silestone Manual, to join the sink tab to the underside of the countertop)."

His secretary ( allegedly) wrote back,saying: " Epoxy will be used to hold sink clips to counter top. Sink is held in place w/sink clips and silicone."

This morning, fabricator calls to "clarify" and confirm all our requests.

He told DH that he does not use Murofix because it is inferior to "silicone adhesive".

He said the secretary made a mistake mentioning clips and said that he will *not* use clips because he has to make a minimum of 14 holes ( 14 because the sink manufacturer, Vigo, apparently specifies that minimum number) to go through the plywood ( 3/4 inch) subtop and the Silestone countertop, for the clips, and that this number of holes would make the whole countertop/sink unit unstable, allowing for cracks to occur.

He also said clips are commonly used for Formica.

He then said that the sink manufacturer's instructions said that it was left to the discretion of the fabricator to decide exactly how the sink would be installed, depending on the material of the countertop.

Finally, he said that if we still wanted clips he would do what we wanted - but , of course, that would be at our own peril.

Please, please, please.... either or both of you or anyone else reading this, please let me know if he is correct or incorrect.

Any fabricators-members' comments will be very welcome.

We have been waiting since August 7th when he did the templating, to get going on the countertop.

Are we being too nit-picky?

Thanks a lot!!!

    Bookmark   August 30, 2013 at 10:18PM
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I am a fabricator.

you might be "too nit-picky". if the fabricator is competent he has a method and procedure for mounting sinks that works well for him. There any many options and most are good. the only thing I don't recommend is adhesive only; I've been called to enough failed sink installs (not by my shop) to know adhesive only is inadequate.

    Bookmark   August 31, 2013 at 9:23AM
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Thanks, oldryder. Yeah, I think you're right and I'll stop nit-picking :-).

Only one thing still confuses me - You say adhesive only is inadequate yet our fabricator says he will use only adhesive. No mention was made of anything else. I'm really scared/worried the sink might one day simply fall.

What do you suggest in addition to adhesive - a support beneath sink like 1 by 4's or 2 by 4's, or brackets or??


    Bookmark   August 31, 2013 at 12:08PM
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any one of several means to mechanically secure the sink are acceptable. if your fabricator said he would use clips in addition to adhesive I'd go with that.

    Bookmark   August 31, 2013 at 2:33PM
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With 2 cm stone that has a ply subtop, the sink lip rests on the ply which supports it. Unless this is a cast iron sink, you really don't need any additional support. If it's a super heavy sink, then your cabinet installer should have built a cradle to support it with it's lip at the height of the cabinet lip, much like is done with a farmhouse sink. Supporting a sink in that manner isn't done by granite fabricators, but by your cabinet installer. You don't want a stone guy doing cabinet work. You want a cabinet guy doing cabinet work.

Only 3 cm stone uses clips attached to the stone. And, your sink manufacturer is trying to avoid a warranty claim by claiming that so many clips must be used. Secondary sink manufacturers often do not manufacture a sink with a straight flat and true lip like first quality manufacturers do. Then they use weasel words to get out any claims by having requirements like that that no one would follow who is used to dealing with a high quality manufacturer. You might want to investigate a more quality sink manufacturer. It's a more permanent commitment than most marriages.

    Bookmark   August 31, 2013 at 2:48PM
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My installer said he puts in wood blocks in the corners to support the sink. After reading here, I ordered sink setter and had them install with those. Blocks probably would be fine, but this is a deep sink and I know how I load it up, so the sink setter gives me peace of mind.

    Bookmark   August 31, 2013 at 2:55PM
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oldryder, thanks! he says he'll use clips only if *we* want them - but then added the caveat that there is a risk of the Silestone cracking, so naturally we are uncertain.

GreenDesigns: What are secondary sink manufacturers? I took 'secondary sinks" to mean additional smaller sinks such as for a bar or island.
Our sink manufacturer is Vigo and it's a pretty good sink of 18 gauge ss with pads beneath to muffle sound.

Our Silestone quartz is 2 cms and will have a 3/4 inch plywood subtop; and since our sink is not cast iron it's good to know from you that we won't need additional support.

marti8a: I was thinking of getting the Sink Setter or asking the fabricator to install the 9 inch shelf supports that willtv's pics above show. Since we will also have a garbage disposer beneath, I remain nervous about the sink being pulled down eventually even though the consensus is that adhesive alone will be fine!

    Bookmark   August 31, 2013 at 3:51PM
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I have been in the quartz countertop business since its inception, and am a Certified Corian Fabricator, Installer, and Authorized Zodiaq installer, and am a colmunist for www.countertopiq.

I have installed at least 20 Hercules Universal Sink Harnesses (available from Braxton Bragg) because fabricators mistakenly believe that silicone or blocking and polyester is adequate to hold a sink in place. IT IS NOT. Sinks must have mechanical fasteners. This is not up for debate unless you'd like to pay me $300.00 to reattach your sink.

    Bookmark   September 18, 2013 at 1:47PM
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