Mold problem in new shower

[Brian in San Diego]

If the weep holes are clogged then the mud bed becomes saturated with water. The wet mud bed then wicks water up the CBU and the walls stay wet and/or damp all the time. Clogged weep holes are the beginning of a swamp in the mud bed.

Notice it took four months to get to this point.

[Tool Guy - Kg]

Scott, you're trying to address this problem by treating the symptoms with that cleaner and suggestion of epoxy grout.

And clogged weepholes puts a whole lotta moisture in the mud bed, of which the walls are buried in. That's why Davy is asking about it. Does it make sense to you?

[Scott_V]

Tool Guy, clogged weepholes is one of numerous possibilities...let's not jump to conclusions until we know for sure what's causing the problem, eh? I had a similar problem with my shower and leaving the shower door opened after showering fixed the problem. And, I know my weep holes aren't clogged 'cause I built the shower pan myself and was careful to place a small pile of tile spacers in front the holes before packing the mud.

The spray was suggested as an interim fix to stop mold growth while root cause was being investigated, not as a permanent fix.

[Tool Guy - Kg]

I don't get it, Scott. In one post you're asking:

Originally Posted by Scott_V

How would clogged weep holes cause mold on a horizontal wall?

I answer....And then you're schooling me.

[Kman]

I could see how a saturated mud bed would due to clogged weep holes could cause wicking up the walls and the front of the bench. But if you look at the pics, there's mold on the back side of the bench. I don't see the connection between that and clogged weep holes.

I'd still like to know what type of backer was used, and whether or not the waterproofing layer on the bench is sloped. Also, I may have missed it in an earlier post, but are there any birdbaths on the floor of the shower, or does the floor drain thoroughly and completely?

[cx]

Originally Posted by ScottV

How would clogged weep holes cause mold on a horizontal wall?

First, perhaps, where would one find a "horizontal wall" on which to promote his mold?

Originally Posted by Kevin

...there's mold on the back side of the bench. I don't see the connection between that and clogged weep holes.

Me, neither.

Originally Posted by Kevin

I'd still like to know.... whether or not the waterproofing layer on the bench is sloped.

Me, too.

[Scott_V]

LOL...I put my foot in my mouth again. I meant to say "vertical" wall. CX, in your experience how far up a vertical wall will moisture wick when the weep holes are clogged?

[scott-wisc]

I towel dryed the tile shower I built every time it was used for 1 1/2 years after I built it, and never had mold. I never cleaned the shower and it looked as good as it did the day it was finished.

[Brian in San Diego]

Originally Posted by Scott W

I towel dryed the tile shower I built every time it was used for 1 1/2 years after I built it, and never had mold.

I squeegee and towel dry mine after every use and I get the same results. It is going on four years now.

[jgleason]

Originally Posted by BSD

I squeegee and towel dry mine after every use and I get the same results. It is going on four years now.

Showoff.

[cx]

Originally Posted by Kevin

I'd still like to know what type of backer was used,

Originally Posted by ScottV

how far up a vertical wall will moisture wick when the weep holes are clogged?

Depends a great deal on the response to Kevin's other question, above, and how much water is being added from the wall above the floor.

[jgleason]

Is that NuTone unit properly ducted to the outside? How long is the duct run? Straight? If not, how many bends?

I'm thinking if the relative humidity stays high in the bathroom, even after running the fan for an hour then your ventilation is inadequate.

[Kman]

These quotes are from the original post:

There is a fan installed in the main bathroom, but water appears to sit on the tile and grout for most of the day.

Fan or no, water should not sit on the tile or grout for most of the day, especially one that has the waterproofing layer directly under the tile. I'm still leaning toward the flat spots/backfalling on the surface and/or the waterproofing layer, and I'm guessing that something besides a cement board unit was used, although I may be proven wrong if we get an answer to that question.

Also, a towel used after we shower remains moist until the next day.

That's not unusual, depending on whether or not it's hung up and what the temp of the room is.