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Grout vs caulk in shower

Posted by patsfan (My Page) on
Sat, Oct 31, 09 at 22:03

I know this issue has been discussed a lot, but I wanted to describe something a recommended contractor told me.

First, we have a 4x8 walk-in shower using porcelain tiles. The house is 5 years old and we live in the midwest. At a 1/2 dozen spots on the perimeter of the floor, on the joint where the walls meets the floor, the grout/caulk has turned black. I'm assuming this is mold or mildew. No matter how much we try to clean, it doesn't seem to get rid of it. So, our plan is to remove the grout/caulk and have someone re-do it. I have referred to it here as "grout/caulk" because it appears to be a clear caulk over the same grout that is used everywhere else in the shower. The shower seems to be in good shape. I don't see any cracks in any of the grout, either on the walls, floor, or the joint between the walls and floor. Structurally, it seems good. It's just that we have these black spots/streaks that are unpleasant to look at.

We called a plumber we have used and he recommended a contractor that specialized in tile shower repairs. When he gave us the estimate he said he had been doing this for like 20 years and can't understand why builders' contractors put caulk over grout. He stated that moisture inevitably gets behind tiles, and the caulk prevents the grout from "breathing", thus causing the mold. His advice was to remove the grout/caulk and re-grout. He would NOT put any caulk over the new grout. He gave us a quote for about $400.

At the time, that seemed like a lot of $$$, so we had another contractor look at it, someone from Angie's list. My wife was home at the time so I didn't get a chance to ask any questions. The quote they left said nothing about grout, only "re-caulk" and the quote was about $350.

Based on what I've read in this forum, it seems that the recommendation is to use caulk wherever there is a change in plane. So, it sounds like we should remove whatever we have there now and apply a caulk that has a similar color to the grout. But what about the concept of grout "breathing"? Why do some spots mold and others don't? I realize that what I thought was a lot of $$$, may not be so. I'm fine to spend the money as long as we're getting it done right. Can some expert help me to feel confident in the correct way to handle this?

Thank you very much.


Follow-Up Postings:

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RE: Grout vs caulk in shower

My opinion? For lightweight shower thinset construction, it's best to caulk changes in plane. For true mud jobs with reinforced corners, it's okay to grout those corners.

If caulk is over grout, the grout can be wetted from behind. The caulk seals the moisture within the grout, not allowing it to dry back in to the shower. That could be the cause of your discoloration.

If you caulk the joint with no grout, water can't penetrate caulk, so no water will be trapped behind or within the grout.

As far as some spots discoloring and others not, it can be how water hits the wall, it can be air circulation or light exposure in that some areas get a better chance to dry, it can be voids in the grout of thinset, it can be areas that have accumulated hair care products or sloughed off skin cells, it can be hocus pocus.


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RE: Grout vs caulk in shower

Mongo, thank you for such quick help.

I don't know whether my shower is "lightweight" or a "true mud job". From what I recall when the house was built, it was framed with 2x4s, lined with some colored drywall-like boards, and the tile was added on top of that. I was told that there was a shower pan under the floor tile, but I wasn't specifically looking at how it was constructed. I trusted the GC. This is a semi-custom, mid to upper end home.

Given that we are trying to get rid of these black stains, would you re-do it as grout only or as caulk only?

Can you comment on the "water behind the tile" issue? If moisture got behind the wall tile somehow and we use caulk only at this joint, would it trap the water and cause mold and then we'd be back in the same position again?

Thanks again for your advice.


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RE: Grout vs caulk in shower

If you walls were built with "drywall-like boards" then that would be "lightweight" construction.

Normally there is a vapor barrier in the wall, between the cement board or drywall-like boards and the wood framing.

Moisture does get through the grout and tile by various means. If it's insignificant, it'll dry back into the bathroom by coming right back out through the wall.

If it's significant or long-term, it'll eventually condense on the vapor barrier and run down the wall, between the vapor barrier and the cement board.

At the bottom of the wall, the vapor barrier is lapped over or in front of the portion of the sloped floor membrane that also runs up the walls. Typically the pan membrane is run up the wall about 8" to 10".

Once the moisture hits the floor membrane, it "flows" through the floor mud and down the membrane slope and out the secondary weep holes that are built into the drain, then down the drain.

Most floor moisture problems are caused because the floor membrane is installed flat on the subfloor instead of sloped to the drain. A flat membrane will simply catch and hold water, saturating the floor mud. This can be indicated by one of several things. Spots on the floor that don't seem to dry. Discolored grout at the floor-wall juncture, or discolored grout along the bottoms of the walls.

So long story semi-short? I don't advocate using caulk over grout. If the grout gets wet, the sealed grout can't dry back into the shower due to no exposure to free air.

Since your shower is lightweight construction, I recommend caulking the joint. Caulk will provide flexibility at the joint, and with it being full-depth, moisture won't get trapped behind it.

Regardless, just ensure that the joint, whether grouted or caulked, gets properly tooled. You want a nice flowing cove from wall to floor. If they overtool the joint and create a slight recess, then water can pool there and cause future problems.

I'm not trying to skirt the issue but there really are no guarantees against future discoloration.

Go Pats!


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RE: Grout vs caulk in shower

We definitely have slope toward the drain. The floor tiles don't exhibit this discoloration, only the joint between floor and wall.

So, it sounds like we need to remove the caulk AND grout from this joint and replace with caulk only.

Our discoloration is black. Is this mold, mildew, both, neither? Just curious.

Thank you very much for your help. I can at least now discuss this intelligently with the contractor.


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5 questions re caulk in grouted bathroom

(1) My contractor grouted the corners of my bathroom and I had wanted them caulked. When I told him this, he said to wait for the grout to crack (if it does) the caulk at that time, whether it be months or years from now. (My grout is unsanded TEC Accucolor with grout lines as close as possible to 1/16" (subway tiles were not the same size). I asked him if caulking over the grout now would be a problem and he said no but I am not sure based upon the postings I have read. Advice? (Bathroom was gutted and furred; building is old and is located in Northeast)
(2) Is grout instead of caulk around the tub OK?
(3) What if the tub has already been grouted?
(4) If caulk is better, is it easy to chop out day old grout?
(5) Is it important to caulk after re-glazing rather than before?

My contractor is coming tomorrow to finish grouting.

Thank you.


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5 questions re caulk in grouted bathroom

As my questions are requests for clarification/confirmation of previous postings, I thought I'd post some pix. (My window sash will be replaced in 2013 but sill, frame and molding is new.)

Thank you for writing again what was written previously.

Here is a link that might be useful: Bathroom Progress Pix


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RE: Grout vs caulk in shower

1) remove the grout first. The caulking needs the joint to anchor itself, or it'll peel back off later.

2) Not at all. It'll crack out pretty quickly. Caulk it.

3) Score out the grout and THEN caulk it.

4) relatively speaking, yes. Hit it with a utility knife, and it should come out pretty easily.

5) Not sure what you mean, but when the tile is done, the grouting should be completed, and that joint left empty, and then it should be caulked as the last step of the tile installation. If you're saying the tub is getting reglazed, I would think that should've been done before the tile got installed.


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RE: Grout vs caulk in shower - UPDATE

Thanks, Bill.

I talked to my contractor this morning and he said:

1. He used silicone at the corners of the sheet rock. He also said the reason he doesn't like to use caulk at the corners is that even though it is supposed to be the same color as the grout, it really isn't, plus the caulk will crack if the building moves just like grout cracks. I asked him about grout behind the caulk and he said he recommends keeping the bathroom dry by using a squeegie/towel where needed, particularly along the top of the tub. The grout looks so nice I guess I'll wait to see if it cracks. It probably will as the roof needs more work and I guess I'll caulk at that time.
2 and 3. There isn't grout at the tub line. It just looks like it as the grout is the same color as the empty space. (That's what I get for looking at it at night.)
4. OK
5. Tub reglazing was put last on the schedule so that it wouldn't get damaged during the other stages. I am going to have them cover all of the walls up to the tile line, and the floor, with plastic.


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RE: Grout vs caulk in shower - Another Question

Dang it! I ordered what I thought was TEC Accucolor Caulk and instead received Colorfast's version.

Could you please tell me if you've used Colorfast's product and if the colors do indeed match TEC's colors?

Thank you.


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RE: Grout vs caulk in shower

They do. I've had this happen directly from Daltile's warehouse, and the caulking has always been right on. Nothing to worry about.


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