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Thread: Undermount sink to granite install

  1. #1

    Angry Undermount sink to granite install

    We just had new granite countertops put in with a stainless steel undermount sink. Our granite installer did the install of the sink and we have had them back 4 times to re-caulk between sink and granite because each time we use the sink, the caulking turns white and eventually falls out. What are they doing wrong? They said they cannot use silicone because it would damage or stain the granite.

  2. #2
    Plumber jimbo's Avatar
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    Something does not add up. Usually an undermount sink is sealed by a bead of caulk on the sink rim which seals against the underside of the granite. Only a very tiny bead of caulking would actually even be visible.

    As far as caulking that joint now, 100% silicone should be the material of choice. It does not stain granite. Whatever they are using is either not compatible with the granite, or with water, or they are applying it to a wet joint.

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    Licensed Grump GrumpyPlumber's Avatar
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    Quote Originally Posted by kellywelch
    We just had new granite countertops put in with a stainless steel undermount sink. Our granite installer did the install of the sink and we have had them back 4 times to re-caulk between sink and granite because each time we use the sink, the caulking turns white and eventually falls out. What are they doing wrong? They said they cannot use silicone because it would damage or stain the granite.
    I've done plenty of Granite undermounts, a few I've installed after the counter guys installed the shields and done my own sealing, silicone caulking is the usual choice for sealant.
    Thats the first time I've heard silicone is bad for granite.
    "The biggest regrets we have in life are the chances we never took."

  4. #4

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    I just talked to the granite installer again and they said they will come back out but will NOT use silicone on it. It will stain it and make it look oily.

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    Licensed Grump GrumpyPlumber's Avatar
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    Quote Originally Posted by kellywelch
    I just talked to the granite installer again and they said they will come back out but will NOT use silicone on it. It will stain it and make it look oily.

    I think they're confusing it with "plumbers putty"...the putty has oils that will seep into granite and especially marble.
    "The biggest regrets we have in life are the chances we never took."

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    Jack of all trades frenchie's Avatar
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    Or else, one of them used silicone on a unsealed granite once, and has been paranoid ever since (it bleeds through sometimes).

    But at this point, it's installed already, I should HOPE it's been sealed...!

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    Licensed Grump GrumpyPlumber's Avatar
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    Quote Originally Posted by frenchie
    Or else, one of them used silicone on a unsealed granite once, and has been paranoid ever since (it bleeds through sometimes).

    But at this point, it's installed already, I should HOPE it's been sealed...!


    lol...I'd have questions 'bout that...
    "The biggest regrets we have in life are the chances we never took."

  8. #8
    Architect Spaceman Spiff's Avatar
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    Silicone is fine, but you just can't smear it around with your finger. Whatever it touches might turn darker. Just do it once and do it right if you're using silicone.
    Spaceman Spiff aka Mike

  9. #9
    Jack of all trades frenchie's Avatar
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    If the stone wasn't sealed, it'll also soak through & darken the backside of where it's applied.

    I once saw an entire kitchen's worth of countertop have to be re-done, because they used silicone to glue it down to the cabinets, but the underside hadn't been sealed, so...

  10. #10
    DIY Senior Member molo's Avatar
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    Is the granite sealed or polished? What do they use to seal it?

    TIA,
    Molo
    "Any American who is prepared to run for President should automatically, by definition, be disqualified from ever doing so."
    Gore Vidal.

  11. #11
    General Contractor dx's Avatar
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    Quote Originally Posted by frenchie
    If the stone wasn't sealed, it'll also soak through & darken the backside of where it's applied.
    Depends on the stone. We rarely seal dark granites, they are not porous at all.

    I have Dakota Mahogany granite in my kitchen, about 10 years old. Unsealed. No stains from anything, including silicone.

    Regardless, sounds like the granite supplier is not real sharp. How many trips should it take to get it right?

  12. #12

    Default It doesnt matter

    Tell the installer that when putting in an undermount sink NO caulking of ANYKIND should be visible from the inside of the sink! An undermount sink still has a lip on it so that the silicone applied can be kept far enough away from the edge so it doesnt show. Who cares what happens to the granite on the underside anyways? And yes, ALL granite counter tops should have a sealer applied to them. Keep in mind that granite is still a stone.

    Tell the installer to get a grip.


    tonysprofessionalremodeling.com

  13. #13

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    Quote Originally Posted by tonykarns
    Tell the installer that when putting in an undermount sink NO caulking of ANYKIND should be visible from the inside of the sink! An undermount sink still has a lip on it so that the silicone applied can be kept far enough away from the edge so it doesnt show. Who cares what happens to the granite on the underside anyways? And yes, ALL granite counter tops should have a sealer applied to them. Keep in mind that granite is still a stone.

    Tell the installer to get a grip.


    tonysprofessionalremodeling.com
    I agree-also use some "painters tape" (blue stuff) around the edge-top and bottom of the gap. Smear it in with your finger-then pull the tape right away. You'll get a nice clean joint line. I also do this on showers/tubs/ sinks- takes a little more time but it looks great.

    Richard

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