grout vs. caulk

Can I use grout between the tile wall and tub? I see references to caulk being used and I have tried that. It never seems to last very long and tends to pull away from the tub/wall surfaces. Any ideas? Chuck B.
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Grout is typically used between surfaces that have no relative movement. I.E. between two adjacent tiles.
You use caulk between surfaces where relative movement is likely. For instance between two items with different coefficients of thermal expansion, or between items that expand differently with humidity. Grout would fail quickly in those applications.
The correct product for your situation is caulk, but it is important to pick the *right* caulk. Don't cut corners by using painter's caulk or another product that really isn't designed to get wet every day.
KB
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Sure, you an use whatever you'd like. It just won't hold up well.
Tubs flex when you add hundreds of pound of weight in water and people. Flexible caulk like the silicone based is best as it will flex with the tub movement. Grout will crack in days.
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Edwin Pawlowski ( snipped-for-privacy@snet.net) said...

Additionally, before you caulk around the tub, fill it with water first. That way, the space between the tub and the bottom of the tiles will be its greatest as the weight of the water will separate the opening.
Caulk at this time and empty the tub after the caulk has had a chnace to cure. With the tub empty, the bead of caulk will be under pressure, but will not come separated when the tub is filled.
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Chuck B. wrote:

There's a certain amount of flex that's required at the tub/tile junction. Grout does not like to flex and will crack. Caulk will last longer - a lot longer if it is done correctly. Almost nobody does it correctly.
The usual way people caulk such a seam is to fill it with caulking. This will not last. Caulk will not stretch in all directions at once. The thickest part of the caulking is obviously the least likely to stretch. Therefore you have to direct the caulk's movement.
Backer rod - essentially a length of foam rope - is inserted into the joint to limit the depth of the caulking. The caulk will be thicker at the upper and lower ends, maximizing the amount of caulk at the contact points of the different surfaces, and thinner in the middle. Basically an hourglass shape. The middle is now the thinnest section and the elongation will take place there. The thicker sections at the contact points also increases the amount of caulk and adhesion at the critical sealing lines.
That is the correct way to do it, and as I said, almost no one does it that way. There are other ways to do it using bond breaker tapes - do a Google if you're interested.
R
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Great post. This is the kind of thing that keeps me exploring the newsgroups.
Bob
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Chuck B. wrote:

Hi, I wouldn't use grout which is hard and not flexible. I always caulk. Like GE Silicone II. This is no brainer. If it puuls away, you did not prep. well before applying caulk. No dirt on the joint, and it hast to be DRY! Tony
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Tony Hwang wrote:

Thanks to all of you for the quick response. All good info. I will use the GE II caulk and will make sure the gap is really clean. Thanks again. Chuck B.
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The responses that advise against grout are mostly right, depending.
If the tile was set into a mortar and mesh base, and you have a cast iron tub (both of which were standard construction in the 50s and earlier), and the tub is on heavy joists near an exterior wall or internal supporting beam, there will be no movement and grout will work. It has held up in my house for 20+ years.
You can also use the grout as a substitute for the backer rod mentioned in another post. Just keep it about 1/8" deeper than a normal grout joint so that you can apply enough caulk. Eventually the caulk will mildew beyond saving and you'll have to cut it out and replace it. If the caulk is just a thin coat over grout, it will be a royal pain to remove.
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Doug Boulter wrote:

That's been my experience given the same tile and tub materials but on top of a concrete slab. Fortunate not to have to use caulking because of the mildew mess and upkeep.
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