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Thread: Grout or Caulk at Tile corners?

  1. #1
    DIY Junior Member scottl44's Avatar
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    Default Grout or Caulk at Tile corners?

    Hello,

    In my last house (tract built 2002), the contractor caulked the joint where the side wall tiles meet the back wall tiles in the stall shower.

    In my new (1956 fixer) house, the contractor I hired used grout in those corners. We have 13" tiles, 1/16" joint non-sanded.

    It seems the grout near the bottom on one side likes to crack. I fill the cracking, but it comes out again. Probably not sticking to the sealer.

    ANYWAY, what say you all? Grout or caulk where the side walls meet the back wall?

    If you say caulk, I guess I should strip out that grout in the corners. But should I cut out some of the caulk where the tiles meet the pan to make sure no water got in?

    The shower pan is a 30" square Florestone with those 1" channels at both sides of the front. Those are open, but the gap between the tile and pan is caulked with silicone all the way around from one of those channels to the other.

    I have read some opinion that some gaps should be left in a few places in that caulk to allow wayward water to escape. If that happens, then it may get in at a spot where there is no gap. So why not just leave the whole thing uncaulked where the tile meets the pan?

    If anybody could set me straight, I'd appreciate it. Thanks!

    Scott

  2. #2
    DIYer, not in the trades LLigetfa's Avatar
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    If you have movement at the corner, you have no choice but to caulk. Around the base, there is the potential for movement so again, caulk is called for. As for a place for water to weep, it can do that at the grout joints just above the caulk.

    When I redid my shower, I used lots of deck screws to lock the framing at the corner to prevent movement. I also used the heavy fibreglass mesh tape on the modified mortar joint of the concrete backer and the corner got a double layer of KERDI where it overlapped at the corner. The tiles met evenly at the corner rather than one tile going behind the other. I grouted the corner and there has been no movement what so ever.
    Last edited by LLigetfa; 05-02-2011 at 05:09 PM.

  3. #3
    DIY Senior Member dlarrivee's Avatar
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    Caulk at any change of plane.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by dlarrivee View Post
    Caulk at any change of plane.
    This is the industry standard as called out in the Tile Council of North American handbook (the industry bible). Now, if you are lucky, you may get by with grouting it. There are color-matched sanded and unsanded caulks for most grouts.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member k9mlxj's Avatar
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    Hi, I have a similar situation (see photo). I'm seeing a gap (crack along existing grout) where the wall tiles meet the pan (floor tiles) in the shower. Thought would just join in instead of starting new thread.

    My question is,

    Do I just leave the gap alone and caulk over existing grout w/ silicone? Or remove the existing grout along the edges where the wall tiles meet the pan before putting the caulking in? Any merit to leave the existing grout around?


    Thx.
    Attached Images Attached Images  
    Last edited by k9mlxj; 05-06-2011 at 12:31 PM.

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Pull the grout (may need a grout removal tool or a knife) and caulk. Depending on what you use, you may have to do this periodically. www.johnbridge.com is a good source of info on tiling issues.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member scottl44's Avatar
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    OK, got it on the change of plane. Strip the grout and caulk it. Thanks!

    But what about what I read about leaving gaps in the caulk where the tile meets the pan? If that's recommended, then why not leave it uncaulked altogether?

  8. #8
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-18-2014 at 07:55 AM.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

  9. #9
    DIY Junior Member scottl44's Avatar
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    That wasn't my picture. My question was the original one. The first one got answered, but the second one about leaving gaps in the caulk where the tile meets the pan, 2 posts up, did not.

    Anybody have an opinion? Thanks!

  10. #10
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by scottl44 View Post
    That wasn't my picture.
    The way this board assigns people the same avatar can get confusing about who's who.


    I thought I answered your question. I would not leave any gap. The vertical grout lines above the caulk will provide all the weeping that is needed

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    A properly built shower should not allow liquid water behind the tile. Any moisture that wicks there should be able to evaporate through the grout lines and not build up. I'd not leave a gap anywhere. Grout sealer, at least most, does not prevent moisture from evaporating through the grout, if it did get wet.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #12
    DIY Senior Member kreemoweet's Avatar
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    In an otherwise correctly built tile installation, the choice of grout or caulk is largely a cosmetic issue. At changes of plane, or where dissimilar materials meet, the use of
    unyielding grout will "usually" result in cracks. It will also "usually" look better. It is a fussy, difficult job to make caulk look good, and many talented tile setters are not inclined
    to bother. The worst thing you could do is smear caulk on top of cracked grout. Leaving an unfilled joint would result in the accumulation of crud, which will soon turn black and
    nasty.

  13. #13
    DIY Junior Member scottl44's Avatar
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    After all this time, I find that the GE 100% silicone I used turns black in few spots and can't be cleaned.

    I was reading elsewhere here that Terry (I think) was recommending polyseamseal around a toilet instead of silicone. Is that also a good choice for the shower where the tile meets the pan and where the tile changes plane at the corners?

    Thanks,
    Scott

  14. #14
    Janitorial Technician nestork's Avatar
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    Quote Originally Posted by scottl44 View Post
    After all this time, I find that the GE 100% silicone I used turns black in few spots and can't be cleaned.
    That "can't be cleaned" business isn't true.

    Hang on, my computer keeps freezing for some reasno
    Last edited by nestork; 09-02-2012 at 01:01 AM.

  15. #15
    Janitorial Technician nestork's Avatar
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    Default No, mildew CAN be cleaned off of silicone caulk.

    Quote Originally Posted by scottl44 View Post
    After all this time, I find that the GE 100% silicone I used turns black in few spots and can't be cleaned.
    No, I own a small apartment block and I clean the mildew off the silicone caulk around my tubs after every tenant vacates. Sometimes, when you get three guys living in an apartment for several years, and they shower three times a day and NEVER use their ceiling fan, it can get to look pretty hopeless, but I find that I rarely ever have to replace any silicone caulk. I don't think I've actually replaced any silicone caulk (cuz I couldn't get it clean) in over 10 years now.

    Read my post in the thread entitled "silicone caulk is not sticking to acrylic tub surface" in this forum (about a dozen below this one) and you'll have your silicone caulk white as Manitoba snow.

    You definitely don't need to know the rest cuz it's really just chemistry trivia.

    The reason they call it silicone caulk and not siloxane caulk (which is what it is) is because of a mistake chemists made when they first started trying to make plastics out of silicon.

    Both silicon and carbon atoms form four covalent bonds, so, just as you have carbon dioxide (O=C=O) which turns out to be a gas, you can have silicone dioxide (O=Si=O) which turns out to form a white powder.

    After the end of WWII, chemists started making carbon based plastics out of petroleum. So they naturally wondered if they couldn't also make similar plastics out of silicon because it formed the same number of covalent bonds as carbon. They discovered that in the silicon based plastics they did make, there were the same number of oxygen atoms as silicon atoms.

    Now, at the time they knew that carbon based plastics formed molecules with long carbon chains, like this:



    so they assumed that a silicon based plastics would do the same.

    And, if you know that there's the same number of oxygen atoms as silicon atoms, you come up with a structure that looks like this:

    |
    Si=O
    |
    Si=O
    |
    Si=O
    |
    Si=O
    |

    Now, here's where I have to go off on a tangent....

    A "ketone" is a class of chemical that has the general structure:

    Something #1
    |
    C=O
    |
    Something #2

    ... where C is a carbon atom and O is an oxygen atom.

    If both Somethings are methyl groups (-CH3) then you have di-methyl ketone, or "acetone" for short. If Something #1 is a methyl group (-CH3) and Something #2 is an ethyl group (-HCH-CH3), then you have methyl ethyl ketone, or MEK for short.

    and here's where I come back from that tangent...

    So, since chemists at the time thought that silicon based plastic was nothing but a long string of Si=O groups, they took the word "silicon" and added an "e" to the end to make it rhyme with "ketone" and thus coined the word "silicone".

    So, it's Silicon Valley, but it's silicone caulk.

    Now, it turned out that their "Si=O" structure for silicon based plastic was actually wrong. The real structure was more like this:

    -Si-O-Si-O-Si-O-Si-O-Si-O-Si-O-Si-O-Si-O-Si-O-Si-O-Si-O-Si-O-Si-O-Si-O-Si-O-

    , only with other stuff bonded to the silicon atoms, depending on what kind of silicon based plastic you have, like this:



    Where the "n" in that formula stands for any number of repeating "dimethyl siloxane" groups. That is, the ugly thing in the square brackets gets repeated over and over again, umpteen to umpteen dozen times in each silicone molecule.

    Still, the mistake stuck, and the simplest form of silicon based plastic is still called "silicone" rubber today. However, the new "corrected" name for silicone is "siloxane", so if you see the phrase "anything siloxane", it means it's a silicon based plastic.

    What you have around your bathtub is actually "poly di-methyl siloxane", or polydimethylsiloxane for short, just like in the picture above.

    Ya gotta know this stuff to be king. It's part of my "How To Be King" correspondence course.
    Last edited by nestork; 09-02-2012 at 01:18 AM.

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