Silicone Caulk Over Grout?

shw001February 10, 2013

I am trying to remove grout from shower areas where floor and walls meet so I can repace it with 100% silicone. Although I have dug into all the grout and broken the connection of the floor to the walls, I am having difficulty removing all the grout. Some of it just remains stuck to the end of the tiles, leaving as much of about 1/16 inch coating of grout at the end of some tiles. I am using an oscillating tool (Rockwell SonicCrafter) and asorted hand tools. Is it necessary to completely get all of the grout off prior to applyng silicone? If I leave some grout, will the silicone stick to it?

BTW, the original contractor put non-silicone matchng caulk over the grout, which grew mold and has been deteriorating. I have mostly removed this, but the grout under it was a lot harder than I expected.

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Yes, the silicone will stick. Did you "touch" the grout tool to those stubborn chips? Also, sometimes a utility knife helps. Caution; if you have a waterrpoof membrane right behind the tile (kerdi, etc.), be sure you don't cut into it.

What size wall tiles do you have? What size grout joints?

While some advise caulking all the joints where there's a change of plane (floor meets wall, wall meets wall, etc.) Personally, I do not caulk the wall-floor joint. The reason is water gets into grout, migrates downward, and that intersection will then stay wet much longer since it can't dry out as easily. That leads to mold/mildew. I grout that joint. If it cracks (not likely), I touch up with grout.

Wall corners are different story. There you can caulk. Grout cracks more easily there.

This post was edited by homebound on Sun, Feb 10, 13 at 19:48

    Bookmark   February 10, 2013 at 7:41PM
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Homebound hits all the points squarely on the head. I wouldn't want to mess with digging out all the grout and risk puncturing the membrane. If any grout found it's way onto the glazed portion of the tile it's never coming off without a utility knife, I would leave it.

A trick my wife showed me to clean and prevent mold on the shower floor is to regularly spray a 75/25 ratio of white vinegar and water after every use,leave it on, no scrubbing. For hard to remove stains on grout spray mixture on and respray once dry for 4 cycles or more depending on stubbornness then give a last spray and give a scrubbing with stiff nylon brush, works better than Spray9 the cleaner I swear by.

    Bookmark   February 10, 2013 at 11:57PM
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Regarding caulking the wall/floor joint in a shower:
wouldn't a caulked joint also allow more water to actually go into the joint during a shower?? So it would be a tradoff between how much could vent after the shower and how much would go in. Also, with 7x7 inch wall tiles and 1/8 inch grout lines for most of the wall, would would there be much infiltration of water behind the walls? This is bafflilng.

    Bookmark   February 12, 2013 at 7:39AM
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As long as it can dry out, it doesn't matter if it gets wet. To illustrate, tile shower floors get wet, too, don't they? Are you seeing mold/mildew problems on the joints? (I hope not.) Case closed.

    Bookmark   February 12, 2013 at 8:52AM
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Thanks guys. This is all very helpful.
I still have not decided on grout vs caulk, but need to soon. Homebound's suggestion to grout the wall/floor joints sounds logical, but it is going against prevailing commentary to use 100% silicone on John Bridge and other sources. Decisions-decisions.

Regarding the vinegar. Someone on this site or John Bridge said to NOT use acidic cleaners. However, I have heard a lot of people pleased with the venegar approach. Just scratching my head.

    Bookmark   February 14, 2013 at 10:13AM
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Vinegar weakens your grout. It is also useless as a germ killer, but popular with the "natural" crowd as a cleanser. It is, however, very good for preventing mold on your cheese and is essential for a good salad dressing. Acid, in the right context, is a good thing.

    Bookmark   February 14, 2013 at 5:02PM
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I'm faced with the same dilemma and I'm not sure whether to use grout or 100% silicone where my porcelain tile meets the cast-iron pan.

shw001- what did you end up doing and how is it holding up?

    Bookmark   February 4, 2015 at 9:00PM
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ALWAYS caulk a at changes of plane. 100% silicone (good quality) is the best.

    Bookmark   February 5, 2015 at 6:14AM
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