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tanner3155
Is caulking necessary?

Hi all, today I removed some caulking from between the tile and tub on a tub/shower. It suddenly donned on me that when the water gets through the grout/cement board and goes back to the tub, how does it get back in if you have that interface caulked? Then I did some googling and found this.....

"It doesn’t need to be caulked at all. Caulking at the bottom of the tub is not a required step, it’s more aesthetic than anything else. Although it does contain more water in front of the surface of the tile, you don’t NEED it."

Even if I left little area's uncaulked (weep holes) wouldn't the water get in behind the caulk and eventually get moldy?

Thanks,

Mike

dj1
Re: Is caulking necessary?

Mike, caulk it. I would.

A. Spruce
Re: Is caulking necessary?

True, grout lines can fail and allow moisture behind the tile, however it is a falacy that it will find it's way to the bottom edge and seep out on its own. What it will do is loosen the grip of the mastic holding the tile to the wall, as well as mold/mildew behind the tile. If you leave the tub/tile joint uncaulked, it too will allow moisture behind the tile and cause mold/mildew and eventual tile failure. Caulking is more than aesthetic, use it and make sure that the joint stays secure. If you notice the caulking starting to crack or fail, remove it and recaulk.

MLB Construction
Re: Is caulking necessary?

spruce is 100% correct. who ever wrote what you read is wrong.

Sombreuil_mongrel
Re: Is caulking necessary?

AArgh! You never put tub-surround or shower tile up with mastic! Thinset mortar only. Mastic-based failures are far more prevalent than successes.

I think there is some truth to the idea that in the old days with 1 1/4" thick mud job tub surrounds, the caulk of marginal quality back then, it was a "wash".
Remember grout lets moisture in AND back out again, it's a revolving door, so caulk at the bottom is not trapping vast amounts of water because it can evaporate via alternate routes.
Casey

tanner3155
Re: Is caulking necessary?

Thanks everyone,

Just trying to understand the water/moisture migratory path. I'm told that the water hits the tile, seeps through the grout to the cement board, seeps through the cement board and hits whatever barrier where it runs down to inside the lip of the tub or pan. If this is correct, then my confusion was how can the water make it to the drain if you caulk the exit (between tile and tub/pan)?

Is this how the mold was caused under my caulk?

Mike

Sombreuil_mongrel
Re: Is caulking necessary?

There is never enough water in liquid, running form to move downward by gravity. Water migrates through the grout in small quantities, and moves from wet to dry, so if the bathroom is kept as the dry side, it will evaporate back out into the room through the grout. The purpose of the tarpaper is to ensure that the insulation doesn't get soaked.
Your concern for this is a real consideration, only it doesn't occur in vertical tiling, it is fully addressed in shower pan construction, where the weep holes at the level of the substrate allow for liquid water to get to the drain, not the structural members. Shower floors see the amount of standing water and larger area of grout lines to make it an real factor.
Casey

A. Spruce
Re: Is caulking necessary?
tanner3155 wrote:

Is this how the mold was caused under my caulk?

The only time I've seen mold behind caulk is when caulk or grout has failed and moisture got behind it. The only cure is to remove the caulk, clean the area really well with a bleach solution, and recaulk.

tanner3155
Re: Is caulking necessary?

Excellent! thanks for the knowledge everyone!!!!!
Now I get it.

A. Spruce
Re: Is caulking necessary?

Glad to have helped. Let us know how it goes.

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