Shower pre-slope discussion

weekendwarrior_2009

15 years ago

Posted by weekendwarrior_2009 (My Page) on Sun, Mar 22, 09 at 19:51

I just spent a day "discussing" the installation of a shower membrane with the guy I hired to retile my master bath. He wanted to install the shower membrane over the backboard. I won that one...it is installed behind the backerboard now. Then I did more research (checking up on him) and asked about the pre-slope and he started with the "in umpty-ump years I've been doing this..I've never" speech. He already layed in the mortar for the shower floor on the membrane and I have that sinking feeling in my stomach. Is the pre-slope a big deal and what is the potential issue for installing the membrane onto the subfloor? He told me that the mortar bed has a slope that will take care of the water. Pardon my tone, but this has been a internet, doing by the book weekend guy vs. the old school handyman kind of week. Any advice? Thank...this is a great forum. I wish I found about two weeks ago.

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RE: bathroom tile FAQ's

Posted by bill_vincent (billvincent@hotmail.com) on Mon, Mar 23, 09 at 9:38

"in umpty-ump years I've been doing this..I've never"

If he started putting it over the backerboard instead of behind it, obviously this moron has no idea of what he's doing. That would've been my cue to fire him on the spot.

Is the pre-slope a big deal and what is the potential issue for installing the membrane onto the subfloor?

Yes, it is, although not many tile installers, plumbers, or GC's realise it. There are two potential issues. First, the given that lends credibility to these issues-- tile, grout, thinset, and mortar ARE NOT WATERPROOF. This is the reason the liner goes underneath all of them.

Now, the first issue is that being that the pan membrane sits flat on the floor, there will always be water sitting in the bottom of the mud base. It needs the help of gravity for ALL the water to reach the weepholes at the base of the drain. With the water sitting there, collecting all kinds of gunk and garbage, it's the perfect breeding ground for mold, mildew, bacteria, and fungus. Is that what you want to be standing on as you get clean?

Secondly, if he set the membrane flat, I'd be willing to bet he just set the cement board in, and dropped it right to the floor, being that it's much easier than holding up an inch or so, so that it's not sitting on the bottom, but so that the mud still covers it. Why THIS would be a problem is that with standing water in the pan, the cement board will act like a straw, and wick the water into it until the water reaches the top of the membrane, where it will spill out and over, causing what appears as a leak.

This NEEDS to be addressed.

Please do me a favor, and post this discussion over on the discussions side, so more people will see it and benefit from it.

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Posted by weekendwarrior_2009 (My Page) on Mon, Mar 23, 09 at 11:44

Thanks Bill for the quick response. Please disregard my e-mail. I will let you and the other members know how this works out. It appears that just putting the fiberglass pan back would be the easiest. FYI, the walls of the shower are tiled down to about 18 inches above the floor so I am looking for the least destructive way to correct this...with a new contractor. Thanks again.

Comments (6)

bill_vincent
15 years ago
last modified: 9 years ago
So, how're you making out?
weekendwarrior_2009
Original Author
15 years ago
last modified: 9 years ago
Bill,

I ripped out the mortar, membrane and lower ~18" of backerboard (again). I am going to re-installing the original fiberglass shower pan. My other post about the treat lumber curb is where I am now. I will cut that out down to the floor due to numerous 3 inch screws and liquid nail the previous guy used to secure the 2x4s to each other and to the subfloor and I pretty sure I don't want treated lumber in the bathroom area.

As for the rest of the bathroom, we have 1/4" backboard on the horizontal surface of the tub deck (on top of 5/8" plywood underlayment) and the vertical backsplash and front surface tiled except grout. I will post some photos on Flickr so you can see what we are doing. Oh yeah, the floor has 1/2" backerboard down and is ready for heating coils and tiling.

On the tub deck....
1. Do you put a grout or caulk line on the corners where the horizontal bull nose meets the vertical straight cut tile or overhang a bullnose piece and grout or caulk underneath?

In the shower...
1. Do you caulk the corners where the tiles meet or grout? I planned on using clear silicone in the corners but have heard that grout is just as effective.

2. When I removed the shower pan during demo, there was nothing underneath. I am now reading that one should lay mortar or foam underneath the pan. You thoughts?
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Thanks for taking the time to find that link enduring. I think that I'm leaning towards the mud bed vs the SLC + kerdi pan. The "tinny" sound of the kerdi pan had me worried (my wife is picky about things like that) lol. The article you linked was a good read and it pushes me further toward the mud pan route. I finally got all of the wonderboard hung today so I will have to make a final decision in the morning when these beers wear off :-) Unfortunately, I messed up hand cutting the kerdi curb so I will have to make a trip to the store in the morning for the materials to do a traditional 2x4 curb. Above: the curb lines up fine on the top plane...just like the 2x4 template I made Below: Unfortunately, i guess I cut the curb at a pretty severe angle...guess this is why I don't do this for a living ;-) I was going to try to cut a wedge or fill in the gap with the dry-pack or something but since this will essentially be load bearing (shower glass door) I feel like that isn't a good option. I figure I will just grab a couple of the curb perfect kits...it seems like the "for dummies" version of shower building so hopefully I cant mess that up...I am so tired of going to the tile store lol.
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bill_vincent
15 years ago
last modified: 9 years ago
On the tub deck....
1. Do you put a grout or caulk line on the corners where the horizontal bull nose meets the vertical straight cut tile or overhang a bullnose piece and grout or caulk underneath?

No, that gets caulked. I don't know why it's different with outside corners, but it is.

In the shower...
1. Do you caulk the corners where the tiles meet or grout? I planned on using clear silicone in the corners but have heard that grout is just as effective.

Caulk it, but not with silicone. Use a siliconized latex made by the same manufacturer as your grout, in the same color and texture.

2. When I removed the shower pan during demo, there was nothing underneath. I am now reading that one should lay mortar or foam underneath the pan. You thoughts?

Although it doesn't HAVE to be, it's to your benefit if it is. You won't get as much flexing out of it if it's filled.
weekendwarrior_2009
Original Author
15 years ago
last modified: 9 years ago
Bill,

I ripped out the PT curb and am awaiting a plumber to reinstall the line for the wedge-lok drain on the base of the shower pan.

I did more reading and noticed that no one has anything good to say about pre-mixed adhesive...well...you guessed it our handyman swore by the stuff and the entire shower (except recesses) and the front and backsplash of the tub deck are tiled with the TEC invision brand type adhesive. I know you can't use this stuff for a shower floor but is it okay on the shower walls? Am I am facing a back-to-square one redo?

Here is a link that might be useful: TEC Invision Website
bill_vincent
15 years ago
last modified: 9 years ago
Let me put it to you this way. It's a crap shoot. If you take it all down now, chances are good you're not only going to wreck the tile, but you're going to destroy the cement board, as well. That's about the worst that'll happen if you leave it up and it fails (which isn't certain). Guaranteed it won't have the same kind of longevity it would if it were installed with thinset, but now that it's up. I'd leave it and let the chips fall where they may. If it fails, redo it then. It won't hurt the cement board.
PRO
Avanti Tile & Stone / Stonetech
15 years ago
last modified: 9 years ago
Just thinkin' out loud here....but I think I'd probably try pulling one or two tiles off the wall and see where it goes. If it's up with mastic, it's probably still so gooey and pliable that it'll fall right off....and if the backerboard is cement, (Durock, etc)and not a fibreboard-type stuff, I don't see how pullin' a tile would damage it at all...meybe a bit messy, but certainly cleanable~~~might even be able to salvage the tiles as well, if that's an issue.

Shower pre-slope discussion

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bill_vincent

weekendwarrior_2009
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Shower pre-slope discussion

Comments (6)

bill_vincent

weekendwarrior_2009Original Author

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bill_vincent

weekendwarrior_2009Original Author

bill_vincent

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weekendwarrior_2009
Original Author

weekendwarrior_2009
Original Author