Undermount sink to granite install

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by kellywelch, Jun 29, 2007.

  1. kellywelch

    kellywelch New Member

    Messages:
    2
    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. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    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.
  3. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    1,404
    Location:
    Licensed Grump
    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.
  4. kellywelch

    kellywelch New Member

    Messages:
    2
    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.
  5. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Location:
    Licensed Grump

    I think they're confusing it with "plumbers putty"...the putty has oils that will seep into granite and especially marble.
  6. frenchie

    frenchie Jack of all trades

    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...!
  7. GrumpyPlumber

    GrumpyPlumber Licensed Grump

    Messages:
    1,404
    Location:
    Licensed Grump


    lol...I'd have questions 'bout that...
  8. Spaceman Spiff

    Spaceman Spiff Architect

    Messages:
    277
    Location:
    Salt Lake City, Utah
    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.
  9. frenchie

    frenchie Jack of all trades

    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. molo

    molo New Member

    Messages:
    840
    Location:
    cold new york
    Is the granite sealed or polished? What do they use to seal it?

    TIA,
    Molo
  11. dx

    dx General Contractor

    Messages:
    156
    Location:
    Michigan
    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. tonykarns

    tonykarns In the Trades

    Messages:
    82
    Location:
    wisconsin
    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. Richard'sRenu

    Richard'sRenu New Member

    Messages:
    15
    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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