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Greg 11-20-2006 03:05 PM

Can you caulk over grout lines in a tile shower?
I put some DAP mircroban caulk over some of the grout lines to waterproof it and fight mold, but now I am fearing this was a mistake. Apparently, the back of tiles need to breath?

I put it along the base where the walls meet the floor, and I also put it on some of the grout lines on the wall (lower third- where i figured water would splash the most).

Now i'm thinking i just should have used Aqua Mix grout sealer.

I'm new to home ownership and new to this board as well. Any advice you all can give me will be GREATLY appreciated.


dougrus 11-20-2006 03:27 PM

Technically speaking, you should caulk any "change of plane" in your tile installation. The idea is that with movement, the grout will crack. Can you grout in these areas? Many people do... and the worst thing that can happen is you regrout or romove it in those areas and then caulk.
My tub surround in my 2nd bath looks like it was grouted in the 60's and there is not the slightest crack in it. All that being said, you shouldnt do both. I would remove it and just seal the grout. Not sure about the science behind it, I just know that is what I have always been told by fellow DIY'ers with more experience than I as well as pros on forums, etc.
Hope that helps.

As a side note, when you do caulk in your shower/tub, I would use 100% silicone Like GE.
The only problem is that it comes in only a few colors so if you have an exotic color grout it is difficault to get a match.

Greg 11-20-2006 03:33 PM

if you don't mind me asking, what is the best product for removing the caulk from the grout line?

is there ever an instance when you would want to caulk over a crack in grout? or would you always want to re-grout?

thanks again.


dougrus 11-20-2006 03:45 PM

A good utility blade and/or small plastic putty knife always works well for me. I cut along the sides of the caulk bead gently and then pull it out with my fingers. I use the plastic putty knife to remove the rest.
In terms of chemical removers I have heard of Caulk-Be-Gone and some other product I have seen that is an adhesive & caulk remover but I have never used them. I guess you use it to soften the caulk and then scrape it out with a plastic utility knife.
If you use a utility blade, be careful (VERY CAREFUL) not to scrape or damage the tub and/or tile.
Others here may have other suggestions as well.

Greg 11-20-2006 03:50 PM

i guess my concern is... there is only a very thin film/layer of caulk over the grout lines... especially in between the wall tiles... no real bead to grab hold old or cut out.

i'm very wary of scraping the grout and damaging it/making more porous.

thanks again for your courteous, well thought-out responses.


Bud Cline 11-20-2006 03:52 PM


Generally speaking you would never want to caulk over grout on the lower 1/3 of a shower or tub surround. Grout will always absorb some moisture, that's just the way it is. You could seal that portion of the grout and all of the grout for that matter. The sealer is intended to be stain and water reisitant but not necessarily waterproof, in fact most all tile sealers are vapor transmissive. This is because the tile and grout does absorb moisture and the moisture must have a means to evaporate, caulk wouldn't allow evaporation to happen.

Caulking the change in plane of all surfaces is the way it is recommended, this would be all of the corners, but in this case those junctures should not be grouted, only caulked.

Caulk is available in every color grout is made in and is easy enough to work with. Silicone on the other hand is more difficult to tool and finish and isn't necessarily for the novice if the finish has to be purdy. There are sources for silicone caulk in most all colors also but it is pricy and usually reserved for high volume users.

To remove the caulk over grout you have installed there are caulk removing products (chemicals) but I have no experience with them and would be afraid of staining the grout.

I suppose it wouldn't hurt to caulk over a crack in grout but the above would also apply. If you have cracking grout then the thing to do would be to remove the offending grout and use grout-matching caulk to do it the next time.:)

Greg 11-20-2006 04:18 PM

Hey Tile Guy
What is the best product for cleaning grout? I read somewhere that cleaners with bleach will actually make the grout more porous. Do you know if this is true?

thanks again.


Bud Cline 11-20-2006 05:20 PM

Greg I'm not sure which products are best, there are many that seem to do a good job. I have never heard of bleach causing porosity that's new to me, I don't see how it could but I'm not a chemist either. Products like Tilex and CLR and those types of cleaners may contain a lite acid and that would in time erode the portland cement that is in most grouts. All in all they are still safe as far as I know.

Maybe the safest is a mild household detergent product. If the grout is sealed it is easier to clean.

Some people keep a squeegie at the shower and dry the walls after each use. This way any hardwater contaminates won't be able to build up and that's probably the biggest enemy.:)

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