Asked on Jan 14, 2012

Under mount s/s kitchen sink coming loose from granite!?

Designs by BSB
by Designs by BSB
My turn for a real tough question! I have a KWC s/s under mount sink with granite counter tops, originally installed 7 years ago. About 2-3 years ago, I had to address this issue - the sink coming loose, so when you rinse out the sink .. it drops down into the sink cabinet.
I had a granite fabricator that came out (paid him $250), cleaned the surfaces and reattached it. We once again had to wait 24hrs before my husband reconnected the sink.
Here we are 2yrs later.. the SAME thing is happening. *sigh* I certainly don't want to go through forking out $2-300 for the same thing .. to only have the same thing happen again. Besides, wondering now if my husband can do it (better?!?). Thanks in advance...
  28 answers
  • Designs by BSB Designs by BSB on Jan 14, 2012
    by the way - it is not held in with clips. Just glue and wood strips (aka the reason for the problem!). Additionally, the original fabricator/installer and the 2nd guy that came out were not from the same company. Needless to say I have a hard time having faith in good granite fabricators!
  • LandlightS LandlightS on Jan 14, 2012
    If your other half is handy, build a brace that will hold the sink in the position you want it in (flush to the underside). Lower the sink and clean as much of the old adhesive as possible from both surfaces. Then apply a bead of PL400 construction adhesive and put back in positin with the brace holding it in place. With brace in place, you can connect the plumbing again and in 24 hours remove the brace. That should solve the proble for you and trouble for the next homeowner if they want to remove the sink at a latter date.
  • Its not uncommon for this to occur. The PL400 will work, but again its going to fail on you. The fix is to add additional supports to the sink. this can be done by cutting wood strips just about the full length and width of the sink. Once the top is set into place with the new adhesive you need to notch the wood strips so they lay flush with the bottom of the sink edge and the granite top at the same time. Once this is completed, using more of the sticky stuff glue these wood strips around the bottom edge of the sink. In effect you making the flange larger so more glue is holding the sink into place. If the sink comes close to the sides of the cabinet, you can cut strips of wood and push them up between the sink and cabinet sides. Then from the adjoining side cabinet use wood screws to fasten the wood blocks into place so the blocks of wood do not move.
  • KMS Woodworks KMS Woodworks on Jan 15, 2012
    I've seen some good fabricators install 2 x 4 across the top and use F clamps up through the drain holes...and set the sink with epoxy instead of pl400
  • Designs by BSB Designs by BSB on Jan 15, 2012
    FYI - removing my counter tops is not an option! I just peeked under there and the wood strips are random sizes.. one of them is even a square piece of ranch casing (eye roll) at one corner Ive never heard of PL400.. but will check it out. The sink is close to the sides of the cabinet, so my thought is to put vertical/standing cleats - securing to the side walls of the sink base. The box is 3/4" plywood, so that should offer enough strength for the cleats. So maybe one at every corner, at the least. Challenge will be along the front edge .. I don't have a center stile between the doors, so I have no where to secure any support here. Wondering how particular we need to be with cleaning the surfaces? Sink will come completely out, so that won't be as hard as dealing with the underside of the granite.
  • Designs by BSB Designs by BSB on Jan 15, 2012
    I can't visual the F clamp, but I will tell my husband about it.
  • I have seen three different ways of attaching a sink undermounted to the granite. a couple are probably beyond practical at this point. First would be to drill into the granite and set a sort of wedgebolt nut into the stone with epoxy. I do not know the name of these exactly, as the granite guys are the ones who do that. When doing that way, they always want my sink and or template before fabricating so they can do that in the shop. Then when installing the granite they just us silicone and several small bolt clips to hold it up tight. Second is a metal bracket available that is made for handling the weight of the sink. It is made to fasten in before the granite is set also. Think of an adjustable bed frame chassis that attaches to the cabinet box frame. You adjust it to fit the sink, drop the sink in, caulk the mounting flange with silicone, and set the granite over it. You can shift the sink around a bit to get an even reveal, then tighten up some screws that are part of the device to drive the flange snug against the bottom of the granite. It might possibly be possible to install one of these after the fact like this, but I imagine it would be pretty hard. Finally is the most primitive. Similar to what you have. The sink is somehow suspended in place ( the clamps mentioned is a good way) while a structural support is added beneathe the sink flange. Obviously the two previous attemps were performed by someone who did not have a clue what it takes to make a structural support capable of handling the weight of a sink full of water, plus the force of scrubbing and useage, or they were depending on glue and only expected their shims to hold long enough for the glue to set up. This is the wrong approach because the metal sink and the granite stone are dissimilar materials. Only a specifically made epoxy would begin to have a hope of holding a bond to BOTH of them for very long. The thinking I follow is the support the sink mechanically and to only use a silicone caulk in the joint to prevent leaks.
  • Designs by BSB Designs by BSB on Jan 15, 2012
    Not knowing what they used to glue it previously.. any advice to what product I should use to clean it? I will share photos when this happens (soon) .. hopefully others will learn from it too! So very frustrating. Both companies that had come out in the past were reputable. (not in my database anymore needless to say!)
  • you may need to use a hand angle grinder with a sanding disk to clean the old adhesive off of the sink and top. It will also roughen up the surface so the new glue will bite better and hold longer. You do not want a smooth surface to adhere the sink to.
  • KMS Woodworks KMS Woodworks on Jan 16, 2012
    here is a pic I found online...that shows the 2 x4 across the top of the counter, in this case they are using squeeze clamps....a F clamp is a type of bar clamp. These F clamps are a bit more powerful than the squeeze type
    comment photo
  • Designs by BSB Designs by BSB on Jul 29, 2012
    just an update .. my husband fixed this.. used PL400 from Home Depot and clamped it and let it dry for 24 hours before we reconnected the sink. In addition we blocks along the sides (bracing it with 2x4s to the sink floor until they dried) and blocks/nailers at the corners where we could reach and screw them into the sides of the cabinets to secure .. indefinitely? :)
    • PSF PSF on Sep 07, 2014
      @Designs by BSB Becky - sounds like I am having similar issues - I have GRANITE composite under mount sink installed on granite counter top and earlier today something did not look 100% right - I looked underneath - some of the silicone is missing and one side of the dbl sink is away from countertop approx 1/2 inch. Did you TOTALLY remove your sink to make this repair OR just replace the silicone and apply brace for 24 hours?
  • Your correct BeckySue. You do not want to rely solely on the adhesive by itself. Using blocking to support the sink where ever you can is the desired method of proper support.
  • Mills Tile & Granite Mills Tile & Granite on May 22, 2013
    for all that don't know, just cut your plywood ruff top (wood the granite itself is glued to) 1/4" short of your template of your sink, set your sink, set your granite on top and your done. never separate never a problem. FYI for bad installers. if you have to go threw all this trouble to set your sinks, you don't know what you are doing or your installer is an amateur in the granite installation trade. 11 yrs in the trade and no call backs. Mills Tile & Granite
    • Tim Tim on Dec 22, 2020

      Are you saying to do this for a repair (a sink that has come loose)?

  • Bobby Daniels Bobby Daniels on Jul 23, 2013
    How do we repair a kitchen sink that has come apart from granite ?, the whole sink dropped .
  • KMS Woodworks KMS Woodworks on Jul 24, 2013
    @Bobby Daniels The normal fix is to pull it all the way down clean up the surfaces and then reattach with fresh adhesive.
  • I agree with KMS on this the correct method is to prep properly refasten and support. What type of sink @Bobby Daniels are we taking about? There are just as many methods to fix as there are sinks.
  • Ulises Huerta Ulises Huerta on Aug 26, 2013
    Hello... I just experienced the same problem as Bobby, my kitchen sink also fell, the sink I have is stainless steel and the my countertops are granite. Is there a special paste that goes into the screws?
  • Sofia Yen Sofia Yen on Oct 18, 2013
    gosh, would love to know as mine's also stainless steel and granite
  • They do not use screws, They use brass inserts. These are tiny pipe shaped fittings that have bolt threads on the inside and a rough surface on the out. The fabricator drills holes that are ever so slightly larger then these fittings. Then using a two part epoxy they glue these fittings into the granite top. Once that is done, they then using small threaded bolts fasten the top into place. Normally they also use the epoxy around the top flange of the sink being installed so it has even more holding power and prevents water from leaking out around the area between the sink and the bottom of the stone top. They also use small bolts that are epoxied to the bottom surface of the stone and then use clips to hold the sink into place. These are perfect for doing a repair while the brass insert type is normally drilled out at the fabricators place to prevent drilling through the surface of the stone.
    comment photo
    comment photo
  • Dow Dow on Jan 11, 2014
    there is a new product out called Cinclips. they attach to the cabinet and up to sink and will never fail if installed as instructed. no glue no drilling, no problems ever.
  • Dow Dow on Jan 11, 2014
    no waiting! hook up and use as soon as they are installed.
  • Amanda Jane Amanda Jane on Nov 11, 2014
    cinclips are great in theory, but if you have a sink in a corner they won't work because you can't reach the cabinet walls. We tried them tonight with our sink and they won't reach :(
    • Dow Dow on Nov 27, 2014
      Not all cabinets are built the same. Sometimes you have to be be creative. How did you install your Cinclips?
  • Scott6836 Scott6836 on Nov 26, 2014
    look for hercules universal sink harness kit. amazon, or attaches to the cabinet with screws. A wire is strung between the attachment points, coming under the bowl of the sink, which is then tightened to hold sink against the counter.
  • Dow Dow on Nov 27, 2014
    CINCLIPS are the fast and easy way to mount a sink. They are also Lifetime Guaranteed! They sell on Amazon , Braton Bragg, Gran Quartz, Cosmos and Fabricators Supply.
  • ECHOFILM ECHOFILM on Mar 15, 2015
    Dow, Amanda is correct, they will NOT work on corner sink bc wall of cabinet is not along side of sink. They are expensive as well, close to $50. I've found that the Hercules Universal sink harness is best solution for corner sinks AND under $10
  • Dow Dow on Nov 24, 2015
    Cinclips are #1 best selling sink Installation system on!
  • Brian Bean Brian Bean on Dec 13, 2020

    We used special metal clip worked perfect.

  • Agnes Chrzanowska Agnes Chrzanowska on Jul 31, 2021

    clips that hold it got loose or maybe they are not there .. make sure to check that