View Full Version : Tiling shower

Mike Armstrong
08-28-2008, 06:12 PM
Hi, I live in southern California, my 1950's home is all wood on a raised foundation. The contractors have remodeled my old shower. It's insulated, the greenboard is up and the floor 'pan' has been hot mopped with tar and the two piece drain is in place. Now it's up to my wife and I to finish it off. It's my understanding, so far, that the walls need some type of backerboard then the tiles can be mudded on.

What I dont know yet is...

1) What do I do next to get the tar floor tiled? I think a layer of thin set or cement to form a nice smooth surface up to the walls, is that correct? After that are the shower floor tiles then adhered to that surface?

2) Should some type of vapor/moisture barrier be put on the greenboard prior to the backerboard? There is no vapor barrier between the insulation and the greenboard.



08-29-2008, 04:51 AM
Posting pictures of your project will help.

The shower area has been drywalled with greenboard (aka moisture-resistant drywall)? Couple other questions, but pictures first...

Mike Armstrong
08-29-2008, 10:40 AM
Thanks Greg, will do.


Sorry but, how do I post pictures?

Mike Armstrong
08-29-2008, 12:23 PM
I'll give it a try...

08-29-2008, 01:23 PM
What is on the walls? If it is drywall, including greenboard, you cannot put tile on that in a shower.

Hot mop is my last choice for how to do a floor. Is it three layers of felt, each layer mopped individually?

08-29-2008, 02:05 PM
It is possible to build a reliable shower with a hotmopped pan, but it should NOT include greenboard. Assuming the hotmop was done acceptably, it should have a slope from the outside towards the drain of approximately 1/4" per foot. If it doesn't have that, you will not like the results.

You must install a mudbed on top of the hotmop - this is a mixture of mostly sand and portland cement (5:1 or so - doesn't have to be exact). If the pan is sloped, then this layer needs to be approximately 1-1/4" thick. Since the floor should be sloped, it would be the same thickness all the way across.

You'd want to first install a vapor barrier over the greenboard (which should not be there in the first place!), then cbu (cement backer unit aka cement board). Run the cbu down to about 1/4" from the floor. DO NOT put any fasteners in the board below about 4-5 inches above the top of the curb. When you install the mudbed, it will lock the bottom of the cbu in place - no need to pierce holes in your liner.

The curb needs metal lath, and fat mud (stickier, stronger mud than what's on the floor). Only fasten the lath (after bending it into a U to fit over the top of the curb with a tail into the bottom of the pan) on the outside - not through the top of the curb. If you over bend it some, it will tend to clamp itself to the curb. Then you cover it with the fat mud. Hopefully, they put a little back slope on the top of the curb, so any moisture that pools there will flow back to the pan rather than outside. Make your mortar follow that slight slope, too.

If the pan is not sloped to the drain, it is wrong, and won't give you long-term satisfaction. There are weep holes in the drain - they must be clear, or water will just accumulate in the pan under the tile. Evenutally, it will smell like a swamp and promote mold.

Hotmopping tends to be a California thing...it can work, but MUST be done right. Most of the rest of the country uses a more conventional method.

For the best help on tiling things, check out www.johnbridge.com (http://www.johnbridge.com).

Mike Armstrong
08-29-2008, 04:06 PM
Thank you for the replies. The shower is small, only 28 1/2" x 59" (small old bathroom that used to have a tub). The hot mop pan was done using multiple layers of felt each mopped individually and sloped to the drain. It was done by an older guy who had been doing it for 40yrs! (he had some God aweful burn scars from tarring accidents, yikes!). I understand a 'mudbed' must be poured and formed over the hot mop. But, before that the greenboard needs to have a vapor barrier or miosture sealant applied to it before the backerboard. I just got back from Home Depot doing some recon. One guy says I should use the roofing felt layered over the greenboard for a moisture barrier. Another guy there, the supposed experienced one, says it's unnecessary to put anything on the greenboard prior to installing the backerboard.

One point. Here in So. Cal at least, it has become a tradition to do construction work as cheap and fast as possible. I'm not speaking being practical, just plain cheap. Most Californians are not there to stay long or are looking to sell the property qiukly and just like the 'average' Cali contractor, could care less if the job was done correctly or how long it's going to last. I've heard it from many friends that that have had contractors do a s---y job and I seen it myself during my own remodel. I had to always preface thew next sub-contractor that I plan to retire in this house so I need this done right. The answer was usually "Oh, well in that case we really should be using this or that". I think hrese guys have gotten so used to doing quick, minimal, shabby work that you have to remind them that you actually do want it 'done right!', for a change.

Point being, the guy that says 'oh you really dont need to do that' is probably used to the quick and cheap job.

I know the backerboard is not waterproof and I 'know now' that hot mopping is not the best but thats what I got to deal with and I do plan on retiring here so I want it 'done right'. Hence coming here to get good advice (wish I would have thought about it 'prior to getting the shower done!).

What type of vapor barrier over the greenboard do you suggest? felt? a liquid sealant?

Thanks for the advice about the lathe on the curb and yes, it is sloped into the shower.


08-29-2008, 05:49 PM
Code requires the shower to be at least 30x30, so if you get this inspected, expect it to fail. It will be about an inch and a half smaller after the cbu and tile. Normally, you'd put 1/2" cbu on the walls. Felt or plastic are equally okay. Lap any seams like shingles so it flows down into the pan.

You might be able to get by with 1/4" cbu on the walls since it is over 1/2" drywall. I think Hardieboard allows that over just studs, but most people use 1/2", so 1/4" over greenboard should have enough support. You'll need longer screws to attach it to the studs through the greenboard.

I'd run this by the people over at www.johnbridge.com (http://www.johnbridge.com). They do this every day...

Mike Armstrong
08-29-2008, 06:02 PM
Thanks for the headsup Jim.

Mike Armstrong
08-30-2008, 10:08 AM
Ok, because not only is the width of the shower too narrow but also the entrance to it is too narrow(23", greenboard to greenboard), even if I rip out the greenboard and replace it with 1/2 backerboard the width's remain out of code. Structurally I would have to tear down the stem wall and move it over and back to get the widths correct which in turn would destroy a perfectly good hot mop job. My boss (the wife) says the reason we initially placed the stem wall where it is was because the old bathroom is so small. Removing the tube and putting in a small shower was to give her (this is her bathroom, we have 2nd and larger bathroom) more room so she (we) dont want to move that wall any farther over in that already cramped bathroom. Also if it doesn't pass code inspection only because it's too narrow who cares, were retiring here, were not trying to sell the house and this is how we want the bathroom setup

So, leaving the stem wall, greenboard and hot mopped pan as is that leaves me with a few of choices.

1) felt over greenboard, 1/2" Hardibacker, Redguard and then tile.

2) use 1/4" Hardibacker insted of 1/2" because the greenboard is already up.

3) no felt just Redguard over the Hardibacker

4) just felt, no Redguard

What do you think?



08-30-2008, 12:11 PM
If you're going to use Redgard, no vapor barrier beneath. You don't want to sandwich moisture between the two layers. Since Hardie says 1/4" is okay on a shower wall over studs, it should be enough support over the greenboard.

Have you or your wife stood in there and simulated showering, bending so you can wash everything? I think you'll find it very claustrophobic. I think I'd have to scrunch my shoulders up to turn around. I had one inexpensive hotel room in London one time that would never meet code here in the US; it was a big pain - glad I was only there for a week; you'll have to live with it for a long time.

Mike Armstrong
08-30-2008, 12:26 PM
Hi Jim,

Thanks for the reminder of why not to use two vapor barriers.

I haven't actually read anything that says 1/4" Hardbacker is ok over greenboard and studs. I have their installation guide handout but there is no mention of that. Is that ok to do for sure and sound practice (ya, I know, greenboard itself is not 'sound practice') for building or is that outside of normal practice? I'll go to the Hardibacker website and check it out.

It is indeed a tight space but this is my wife's bathroom and she's a small gall that will probably shrink even smaller with age. She is fine with the width now that the big bathtub that aws in there is gone and she now has ample room outside the shower.

Mike Armstrong
08-30-2008, 01:47 PM
According to the Hardibacker website, 1/4' can be used on walls, it just doesn't say in what circumstances. ?

08-30-2008, 03:10 PM
It is implied that it can be tiled after being attached directly to the studs. WIth the additional support of the greenboard, it should be stiff enough. Just make sure you attach it to the studs, not just to the greenboard. You may need to search out longer screws. Most of the other 1/4" cbu is not as structurally strong and tends to crumble at the edge when you attach it if you get too close.

Mike Armstrong
08-30-2008, 03:36 PM
I guess another consideration when deciding 1/4" vs 1/2" is the tile, specifically the tile piece (I dont know the proper name) the would round over the edge of the protruding Hardiboard. Googling up a few threads revealed at least a couple folks saying that using 'standard' tile you will need that 1/2' protrusion for the average tile end piece to fit properly,?

08-30-2008, 04:30 PM
You're thinking of a mudcap. There are other ways to do this. Check out www.johnbridge.com (http://www.johnbridge.com) for some other help with tiling.

Mike Armstrong
08-30-2008, 05:15 PM
Thanks Jim.