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David H
02-17-2003, 03:07 PM
John and tile experts.
What a great site! I have a few questions regarding the construction of a shower base and a question or two about the walls.
This will be a neo-angle shower built over a concrete sub floor in my basement. The angle walls will be 3/8th glass. The back walls will be covered with granite.

A base has been built using concrete in formwork. There is a short 3-1/2" base for the glass angle walls.

My Dad is helping and has built this concrete base. The floor slopes to the drain. The top of the base slopes slightly inward. This is good but he believes that the mortar/ concrete (we used sacrete which is a premix concrete with small aggregates in it - we also added additional cement to it to strengthen it and mixed it with latex) will create a waterproof base. The thinset would be applied directly to this which would bond the 2x2 floor tiles. The type of drain selected was not the type normally used with mortar shower bases (i.e. weep holes). It looks like the type that would be used on the prefabricated shower floors.

I have some concerns as this does not match the type of construction that I saw in Michael Byne's book i.e. pvc pan secured by roofing cement and lapped up over the base as well as extended up the back walls.

What is your advice?

Also, I have a question regarding the type of support that is need for putting granite tiles on the back two walls.
The walls have 2x3 studs on 1' centers with three rows of blocking. The studs are screwed directly to the concrete block wall and they are very rigid.

Now what is the next layer to be attached to the studs?
Is cement backerboard strong enough to support the granite slabs?

Next is the waterproofing behind the backerboard where it meets the shower floor. The plan is to pack the bottom 9" of the two back walls will the mortar/ concrete (described above). This would create a strong base behind the cement backerboard.

I have seen the textbook way of lapping the pvc pan up the wall just behind the backerboard.

I'm not sure but my Dad may be thinking of using silicon to seal the bottom edge of the backer board to the mortar wall.

What do you suggest?

Is it still possible to work in a pvc pan? The problem is at the drain. The top of the drain is inserted flush with the mortar bed. The actual toppart of the drain screws in with a gasket.

Do we need to chip this out? Much thanks.

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02-17-2003, 03:36 PM
I assume this bath is a first floor bath, slab on grade. Please give us some basic information.

Your base will leak. Concrete loves water and will absorb it like crazy. If used regularly, it will become a water soaked mold breeding mess. If slab on grade, no worries I guess, 'cause it leaks onto the slab. After 6 months, it would be like the army showers I used in Nam. I'd shower in slippers.

There is no way to work in a pan membrane at this stage without ripping out the drain, which you can do, and install a 2 part clamping drain, then membrane over the base Dad poured, and go from there.

If the 2x3's are tapconed into the CMU, then they will support the CBU, which will support the granite. I am not sure I would use granite in a shower. It is fairly porous. I like porceline tile.

02-17-2003, 03:39 PM
David, This is one of those scary posts.We certainly do not want to offend your father,especcially after the amount of work he has already put in. So lets start by saying this:There was a better way of doing things ,however we may be able to save you yet with a surface applied membrane for your pan.A surface applied membrane by laticrete or C-cures 963 prored Painted on the slope and up the walls 8-10" 2 coats will keep you from having a leaker. Now before your father says its not necessary i suggest you do a leak test on what you have.Seal the drain area with a couple layers of duct tape and fill the pan with water.when it leaks (and it will most likely within 24 hours) he will then realize he missed a step and we all get out of offending him and you can suggest the paintable surface membrane.

As far as your granite goes,You mentioned Slabs.How large are we talking here??

When you use a surface applied membrane you will find no need for silicone where the wall meets the floor.Just make sure you pack that membrane material in there!!

Hope this helps!! :)

David H
02-17-2003, 08:43 PM
First, answers to your questions.
1) The 2x3's are screwed to the wall with concrete screws. I'm not familiar with tapconing but we have some blocking on the flat which is well secured to the studs and we've used concrete screws to secure the blocking to the wall. The studs are on 1' centres and the blocking is about 2-1/2' apart.

2) The floor is slab on grade. The visual image about the army showers in Nam makes a strong point about correcting this before we get any further.

3) The granite for the back walls is 12"x12" tile and standard thickness (about 1/2"). I know what Scooter said about the granite being porous but I will seal it well and maintain it.

Thank you for the advice about the leak test as well as the paintable surface membrane. I will definitely go with that unless a more complete correction is made. Does the thinset go directly over the membrane?

I am still worried about the drain area and chip out around the drain and install the proper drain. I like the idea of any excess water leaking through the grout getting out through a weep hole. However, I am treading lightly as I am getting assistance on this job from my Dad.

Thanks again for all of your help.
Regards, David H.

02-18-2003, 07:44 AM
Yes David,with a paintable membrane the thinset goes directly over the top.
Is there a way you could file weep holes into your drain right now before applying the surface membrane?fiole grooves then run the paintable right over the top and into the drain.This way any moisture that does get to your membrane has an doesnt need to be much,just dont fill them with the paintable membrane. If you notch the gasket that may even be enough.
Let me know what you think, i cant see it from here :)

David H
02-18-2003, 04:04 PM
I was thinking the same thing regarding creating weep holes in the drain.
It would be easier to show with a diagram but I am certian there is a way to make it work. Thanks again.

John Bridge
02-18-2003, 04:05 PM
Hi David, Welcome. :)

First, I've got to get this off my chest. Scooter must have been in an R&R camp in Nam. My shower was a one-man canvass affair with wood pallet for a floor. :D

Just kidding, Scooter.

The only drain I know that is specifically designed to accept a surface applied membrane is the Schluter Kerdi-drain. It has a wide bonding surface built in at tile level. It is a bit pricey, but it works and looks good. It will work with any surface applied membrane, including those mentioned, as well as with Noble Company products and of course with Schluter Kerdi-mat. :D Click on products.

It would be necessary to chip out the center of your floor in order to install the drain.

David H
02-22-2003, 11:27 AM
John & other tile experts,
Once again thanks for the great advice!

I am going with the laticrete and the Schluter kerdi drain. For a while I debated about trying to get the laticrete to bond to the 3/4" rim of the existing drain but decided that its better to do it right the first time and break out the drain and surrounding concrete and put in the kerdi drain. (I'm doing this over a concrete slab floor). John, you're right it is pricey but it looks good (for a drain).

Anyway, Just got back from the store and plan to install them this afternoon. I need to review the instructions - if I can't figure them out I will be back for help. I need to make sure which one goes in first.

Any tips would be appreciated.

Another question or two....
1) I bought the laticrete mini kit which comes with 40 sq. ft of membrane. I need 16 ft for the base floor and kerbs which leaves 24 left over. Should I do the bottom three feet of the back walls with this? I'm using CBU for the back walls.

2) I was thinking of running the laticrete membrane up the back wall behind the CBU (about 4" up the back wall). I was then going to bond a piece to the floor and run it up the front side of the CBU and I have enough to do the bottom three feet as each back wall is 4 feet wide (the front walls will be glass neo angle). Will the top of the 3 foot section create a problem for the tiles as it will be a small ridge running across the wall at about the 3 foot mark. (I'm using 12x12 granite tiles - I could cut the membrane at 2.5 feet so it hits the middle of a tile).

Thanks again for all of your help.
David H

David H
02-22-2003, 11:48 AM
Just so there is no confusion on one of my questions above - the 12x12 granite tiles are for the back walls and the floor tiles will be either 1x1 or 2x2 ceramic.

David H
02-22-2003, 05:20 PM
Another Question.
Now that I've reviewed the laticrete instructions and the installation cd that came with the kerdi drain, it looks like I should put the CBU board on the back two walls prior to applying the laticrete. Is this correct? My earlier thinking was based on the PVC waterproofing system where the liner goes behind the CBU. Here it looks like you want to water proof the surface immediately below the thinset.

This is what I am planning on doing.
1) Install the kerdi drain. Let the mortar set. Protect the drain with a piece of cardboard.

2) Put in a vapour barrier on the back two walls. The back walls are 2x3's tapconed into concrete block walls.

3) Install the CBU board on these walls. It is hard to find galvanized screws so I was going to improvise with deck screws (they are a brass colour). The back walls are 4 foot widths and 7 feet in height. The only joint inside the shower is at the back corner where they meet. Do I finish this with some thinset over tape? Is the fiberglass tape used for drywall good enough? I couldn't find the one mentioned in John's book at HD. Also, do I do anything special at the plumbing holes?

4) Install the laticrete membrane system. This way, I could run the laticrete membrane 6" to 9" up the back walls. Another question. The width of the membrane material will require me to have some joints. How does this sound? The width of the membrane is 37 inches which is about four inches narrower than the shower. I could center it and have a two inch gap on each side. Then I could finish the corners and overlap the membrane. I think that I should do the centre piece first and then the back wall corners and the kerbs (neo angle).

Thanks for your advice. By the way how do you make the smilies work?

I'm doing this tonight and tomorrow. So far I spent about an hour chiselling out the concrete around the existing drain. Now to figure out how to cut it off??

I'm taking pictures as I go. When the bathroom is completely finished I'll post a few photos. This will never compare to D. Swallows kitchen post. John should have some form of academy tiling award for him. I think that his project qualifies as an urban legend. It really is amazing.

John Bridge
02-23-2003, 09:59 AM

You may be well along by now, but here goes. I think you've got the idea with the membrane. It does go inside the cbu walls, and it can go as high as you want but at least 3 inches above the top of the curb.

The screws should have been cbu screws. Deck screws won't hold as well, so put in plenty of them.

The tape is sold right where the CBU is sold. It comes in a small box. The roll is only 50 feet long and it's expensive.

The Kerdi-drain must be completely supported with mortar, and it must be set level.

David H
02-23-2003, 12:05 PM
Thanks John, I was starting to wonder when I wasn't getting any responses. I guess there are better things to do on a Saturday night.

Actually, I am not that far along. The concrete break out took me closer to 2.5 hours to break out. I had to make the circle about 2.5 inches bigger than the drain so that I can get the mortar under it. This was really strong concrete. When I install the new drain, I think that I will put the mortar in a heavy freezer bag and nip a corner. That way I can put some pressure on it to get it under the rim of the drain and down by the pipe. I will also be careful about getting it level and flush with the floor.

The kerdi drain cd video showed the guy sticking the flanhed drain overtop of a pipe. He didn't set it with the ABS sealer. I had to get a size converter to reduce the drain from 2" to the 1.5" of my drain pipe. I assume that I should use the cement to seal it all together. (I will check the fitting carefully before locking it in place as you only get one shot at it).

I haven't put the cement backer board up yet so I can still get the correct screws.

John, when you said that I should run the membrane on the inside. Dumb question but I want to get this right. This means inside the shower area - correct? Not buried in behind the cement backer board.

Thanks so much. I seem to find new ways to make this project very difficult. If I could start over again - I would have done my homework a lot better and I would have tried to think through the process to its finish. Anyway your help has been great!

David H
02-25-2003, 02:51 AM
Just wanted to confirm that the CBU for the back walls goes up first and then I use the laticrete to seal the concrete base and curbs.

FYI - The old drain is out and the kerdi drain is in.
2 hrs to knock out the concrete around the drain.
6 hrs to cut the old drain out and cut down the PVC drain just enough for the Kerdi drain to sit flush with the concrete base. Most of the time you just keep on measuring as the last thing that you want to do is cut off too much of the drain pipe. The PVC was in a hole so I used a tiny dremel cutting device that actually fit in my drill. I don't know how I would have done this without it.
The drain is in and finished with mortar. I packed the underside of the drain for good support.
I did about 15 practice runs on putting the drain in prior to actually using the solvent. Its harder to level and match with the existing floor than you would think and once the solvent is on you have about 15 - 20 seconds to get it right.

Thanks again for all of the advice.

John Bridge
02-25-2003, 07:18 AM
Yes, all the backer board goes up everywhere before the shower is waterproofed. The waterproofing goes on the surface and the tile is bonded to it with thin set. So get everything perfect before you start with the Laticrete.

David H
02-25-2003, 08:25 PM
Thanks John,
I installed the CBU with rockhead screws. They worked really well. I put them in 1' foot apart.
One note for any other amateurs doing this for the first time is to take measurements of the location of your copper pipes. I scared myself when I put a screw in the wrong spot and had a chance of hitting a pipe.
I pulled off the CBO and fortunately missed it by three inches. I had planned to do a schematic diagram with measurements of the copper but got carried away after cutting the CBU and put it up without thinking.
Now, I'm off to do the laticrete. I have to cut all the edges and some special corners for the neo-angle curb. I watched the kerdi drain cd about 20 times to figure out all the cuts for the walls and corners.
Hopefully, it will come together quickly tonight so that I can get on to tiling the shower floor tomorrow. (I'm using 1x1 ceramic tiles for the shower floor).

Question about thinset and installation of granite 12x12 tiles for the back two walls.
Is there any problem with using the marble and granite medium set (white) for applying the granite on the back two CBU walls? I've seen the posts where people are told to use regular white thinset and to save the money as it works just as well. But is there anything wrong with using the specific marble and granite mix?
Second question - if using regular white thinset - do you just follow the directions or do you replace the water with latex liquid? (Or go 50 - 50 water / latex?).
I'm worried about the granite sticking to the walls and might just do three feet in height at a time.
I guess the right question is - what is the best technique?

Thanks, I'm living on caffeine these days.

John Bridge
02-26-2003, 06:23 AM
Hi David,

Don't work yourself into a frenzy. That's no fun, and you're supposed to be having fun. ;)

The marble set is fine.

The Schluter drain is adjustable laterally and vertically, remember.

Slow down. ;)

David H
03-01-2003, 06:09 AM
Thanks John,
The laticrete went on very easily. I found that the trick was putting on a liberal coat of the liquid and doing the equivalent of backbuttering the small pieces of cloth membrane on the curbs. They stuck better. I cut all my pieces and I would suggest that anyone trying this to watch the Schluter drain video (its on their web site) as they show you how to cut the kerdi material. Slightly different product but the same principle for the cutting.

I made the mistake of starting three different threads early on - so now that I've committed that sin, I'll have to jump over to my thread related to sealing granite to tell you about that.

The short and the long of it is that I purchased a light coloured granite tile called Imperial White. I did some stain testing on it i.e. lemon and olive oil and came to the conclusion that this granite must have been a sponge in a former life. :) I used Bulletproof by StoneTech on the recommendation of KChurch and the restorer from Colerado.

Anyway, I think that I can slow down now.
Thanks again. You helped me through a really difficult phase of my project.