How To Install A Pre-fab Shower Pan [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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10-08-2006, 02:34 PM
First of all, I’d like to say that this site has a wealth of knowledge and I am humbled to realize how much more there is know and understand. You thoughts and advice will be welcomed. I’m redoing the tile shower in my master bedroom and maybe the floor. Two part question:

Part 1 Deflecto calculations:
The bedroom is over the garage and the area under the floor joists is dry walled with a perpendicular girder for support at about 12’, the remainder is 2.5’ to 3.5 feet to the exterior wall (15' in living space). The flooring is ¾ plywood. The joists are 2x10s, 16” OC and the span is somewhere between 12’ 6” and 13’ 2”, probably closer to 13’ due to I can’t measure exactly. They are marked “S-DRY HEM FIR”. I’m assuming they are Douglass FIR. See pic. They pass deflecto with L/458. If I assume they are not they rate L/350 for 13‘ and L/386 for 12.5.’ Is there enough margin in deflecto for a passing assumption?

Part 2 Shower floor damage.
I removed the fiberglass shower pan so I can install a new Swanstone shower pan. Unfortunately, the drywall was not the only damage. The floor beneath is rotted and needs to be replaced. See pics. The floor joists run left to right with two underneath the shower floor. To the left is a closet wall (with plumbing) just out side the bathroom entry. Behind the far back wall is the master bedroom. To the right is the end of the floor – top level of a tri-level so the floor stops there. The flooring on the other two sides of the shower walls look very good. Some small stains on the bedroom side, closet looks fabulous.

I'm thinking I'll cut up the floor exposing 3 bays and run cut 2x10s or 2x6s front to back square up the nailing surface. See the red sections in “floor joist addition”. I wa this a good idea? Do you all have any suggestions?


P.S. I plan on installing a standard drain with the Swanstone pan into existing 2” PVC drain.

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10-08-2006, 06:19 PM
how are the joist in good condition the blocking running perpendicular to the joist isnt neccessary but doesnt hurt either sounds so far...

10-15-2006, 01:22 PM
My shower is a three sided stand-up shower. Each wall is an interior wall, with 1/3 of the upper postion of one of the wall up against the attic and has insulation. Do I need a vapor barrier on all three walls, just the portion that is along the attic wall or none at all?


10-15-2006, 01:38 PM
Vapor barrier on all three walls... If the insulation on the attic part has a paper or foil face, make numerous slits through it so you dont wind up with 2 vapor barriers back to back. I personally use 6 mil poly sheeting, available at any big box or hardware store, and I wrap the entire shower with one big piece. Make sure the vapor barrier lays over the pan liner, or the lip on those acrylic shower pans.

10-15-2006, 01:49 PM
Welcome, Tom. :)

I've merged your two threads here since it looks like it's all one project. Bookmark the thread so you can always find it and post all your questions here.

Don't know why you were overlooked on the first thread. When that happens, just make another post and the thread will rise to the top of the queue for attention.

1. Your joists should be fine for a ceramic tile installation. Our Deflecto is pretty conservative, actually.

2. Your repair plan looks OK.

You must have a moisture barrier behind all walls in the shower, interior or exterior. If I understand correctly, part of one wall actually becomes the sloped roof/ceiling? Or is that top part just a knee wall in the attic space?

Either way, Alex (Splinter) has given good advice.

My opinion; worth price charged.

10-30-2006, 07:27 PM
Thanks for the advice! Vapor barrier all the way around.

CX, yes a knee wall, think tri-level - have you been to my house? :D

I now have a city permit to continue my work. Better safe than sorry and I can always use another set of eyes and opinion/inspection.

I removed the old floor and I am ready to plop in the new one after the inspection. I've roughed in the new plumbing, sistered the joists with 2x10s and checked the drain is 2" PVC.

Anything I should watch out for or be prepared for the inspection? Plumbing height, drain issues, floor issues? No electrical changes, just new floor and copper.

Any words of wisdom welcome. :lol2:

More pics for your amusement...


10-30-2006, 08:41 PM
Don't know what you plan for wall board, but are you sure you've got your mixing valve positioned such that your plastic guage will be flush with the finished tile surface?

Looks to me like you've got more than 16" oc spacing betwix a couple of them studs on the water wall and maybe the same situation on the opposite wall - the wall with the really wimpy R-11 insulation.

If you're doing a traditional mud and liner pan, you need more blocking for the pan liner. Also need to notch or fir the studs for the liner.

Is all I see at a glance. We've got some sharp-eyed peoples hereabouts, though, so you may get some more comments.

My opinon; worth price charged.

10-30-2006, 09:04 PM
If you go with backerboard i would suggest moving the valve out to
1" from the plane of the studs. Usually theres a note on those cover
plates stating "this surface must flush with finished wall. 1/2" backer
board and 1/2" of tile gets you close to 1". If your doing stone or another
material that is thicker just make the obvious adjustments. Cx is right
on the money. Get the valve moved out, backing looks ok accept for the
wall with the pipes in it. good luck

11-11-2006, 02:21 PM
Thank you all again for the advice. Hamilton was right on with that valve. It was barely 3/4" out. I redid the mounting and now it's 1-1/16" inch past the studs.

I could not put a 2x4 stud on the water wall since I couldn't get is flush with the other ones. Hopefully that will be OK with the CBU? There are four studs on that wall already. On the other wall the studs go 10" to 16" to 20" OC. Again I haven't tried to install a 2x6 stud there either, but I may sister up the last stud to give me a better nailing surface.

The city inspector came by and signed off the project as it is. I'm a bit pissed since he said he "didn't know why they issued a permit for this?" He inspected the plumbing and the floor/framing and told me the electrical didn't need a permit and sent the electical inspector back without even entering my house. Oh well, $200 donation to the city of Westminster CO!

I could use some shower pan advice. Swanstone reccommends:

"For a more stable installation, it is suggested that the shower floor be nested in a bed of mortar-type material (Quikrete)."

I guess that's your basic mortor on a 1/4 trowelled bed? Nothing special since it's in a dry area (hopefully)? I want to do this since the new pan seems much less substantial than the one I removed. The old one was thicker, heavier, but was not cemented down to the floor.

Splinter said "Make sure the vapor barrier lays over the pan liner, or the lip on those acrylic shower pans." So that means under the CBU, down the wall and then feed it into the shower pan? So then its pan-vapor-mortor-tile sandwhich?

More pics you your amusment.


11-11-2006, 02:26 PM
Here's the pan in place.

11-11-2006, 04:28 PM
I could not put a 2x4 stud on the water wall since I couldn't get is flush with the other ones. Hopefully that will be OK with the CBU?Nope, not gonna be OK. Read the manufacturer's instructions for your CBU. Every one I'm familiar with require a maximum stud spacing of 16"oc. And I see no reason at all from your pichers that you can't add some more studs. :scratch:

For setting the shower receptor, get you some Mortar Mix or Mason's Mix from Homer. You want to make a big bed of the stuff across the entire footprint of the receptor and thick enough to moosh up into all the voids in the bottom of it. Prolly an inch thick or more. Then just moosh the base down into that, level it perfectly, and leave it alone until the mortar has a chance to set up before you do anything else in there. Overnight at least.

On the moisture barrier, I prefer to see the wall board down over the lip of the receptor, too. But lots of instructions allow stopping the board above the lip and having only the barrier over the lip.

You'll notice that the instruction drawing you posted shows no barrier at all and just sheetrock to the top of the receptor lip. You wanna follow those directions, you're on your own. :shake:

11-11-2006, 06:44 PM

I looked at the stud that I was trying to use and it had a slight warp to it. The bowing is probably the reason it wasn't flush. I'll redo it again tomorrow and let you all know how it goes. Hopefully, I'll get it all framed out and the mortor set so I can watch some football.

Th only problem that I see bringing the CBU all the way down beyond the lip is that it's not flush with the wall. The gap between the pan and the wall is 3/16" and the lip is 3/16" so the CBU will sit right on the edge of the lip instead of dropping down. Unless I shim the entire stall? :scratch: But then again, the design above was the one that got me into this mess in the first place! :bonk:

Enough for today, time for :loaded:
Stay tuned. Thanks, CX

11-11-2006, 07:31 PM
I would try to find a fairly straight stud to add to the valve wall. The best way is to remove the two blocks and reinstall them after the new stud is added. You probably can get by with notching the stud around the blocks, be better than leaving a large gap like it is now. :)

11-11-2006, 08:17 PM
Thanks Davy.

Got motivated this evening. Can I have my framing merit badge now? PLEEEAASSE? :yipee:

11-11-2006, 08:25 PM
You some kinda politician there, Tom? Lessee that other wall before we be handin' out any merit badges, eh? :D

11-11-2006, 08:37 PM
Lessee that other wall before we be handin' out any merit badges, eh?

I knew you were gonna say that! :yeah:


11-13-2006, 12:21 AM
Update for the day. I laids the mortor bed and installed the shower pan. For reference, I used 30 lbs of mortor - could of used 40-50 easy. Hope it suffices.

11-13-2006, 12:22 AM
Since I lack a toilet, there is no reason I can't have a throne. :clap2:

John Bridge
11-13-2006, 05:58 PM
Very good, Tom :) Looks like you have it going your way. :)

11-13-2006, 06:08 PM
Thanks John. P.S. I just placed an order for your book. It may come too late, but I got other projects to do.

I'm still fretting about the lip around the pan. I'm a perfect 1/2" from the framing all the way around, meaning the CBU will not drop down into the pan. This is the way it was before, and obviously it caused problems. However, it was just gypsum board behind so I am improving it. I am a slave to the original framing due to extended wall on either side. I guess I'll just have to live with it and take the wrath of the forum. :stick:

11-13-2006, 06:13 PM
Oh yeah, any chance of changing the title? I'm no longer confused about vapor barriers. How about "Water damaged shower and floor repair with new porcelain tile"


11-13-2006, 06:45 PM
Do the wall construction correctly, Tom. There are always ways to deal with trimming out the edges.

My opinon; worth price charged.

That title won't even fit on the page. :D

How 'bout Tom's Leaky Shower Project, or something similarly mundane?

11-13-2006, 08:28 PM
Well I don't want to replace one leaky shower with another leaky shower!

I'm totally confused what to do? Here are more examples of shower pan installs from manufacturers that show CBU above and below the lip and various ways to water proof it. Then there's this guy who lips it over but doesn't say a word about how to fur it?

Why not just run a strip of Kerdi across the bottom? :x: I can't believe I just said that!

How about renaming it "How to install a prefab shower pan"?

11-13-2006, 08:36 PM
You just need to add some furring strips to the edge of each stud, Tom. Whatever thickness you need so's the CBU will lap over the edge of the receptor. Rips of plywood is always my material of choice for such extensions because it is uniform in thickness and doesn't split when fastened.

You can do it with the CBU stopped above the receptor so long as the moisture barrier drapes over the receptor lip, but I still like it better with the wall board and the moisture barrier over the lip.

My opinion; worth price charged.

11-14-2006, 06:46 PM
Thank you CX. I appreciate your input.

I have a question about the wonderboard CBU. The manufacturer's instructions state to "Fasten Wonder board panels to studs every 6"-8" and around all edges." That's fine for the vertical studs, but what about the horizontal edges? That would be every 16" unless I need nailers at every horizontal seam?

11-14-2006, 08:29 PM
Welcome, Jason. :)

Please start a thread for your project. While it seems like a good eye-dee to just axe one more little question on someone else's thread, it really gets confusing for all concerned when it turns into more than that. Which it always does. :shades:

We'll be able to keep up with the history of your project and give you more meaningful answers that way. :)

Even more reason to have your CBU over the lip of the receptor in your case. Mandatory, in fact, as far as I'm concerned.

My opinion; worth price charged.

11-14-2006, 09:55 PM
Thanks CX. I didn't want to go down there with my 10 Gallon Hat, Big White Horse, and Shiney Badge to enforce the law! :whip:

That be a reference to one of my favorite Texan, Lyle Lovett, that is next to you my friend. :tup1:

11-28-2006, 10:41 PM

And thank you all for you valuable input! This site is great and all the information is superb and I have learned so much. Here is the progress to date:

I redid all the framing with both vertical and horizontal 2x4 supports so the all the edges of the CBU had a nailing surface. I installed the vapor barrier, one big 10'x8' peice. The CBU went in next and I framed in my overpriced duk liner for the niche. I taped and mudded all joints with Mapei Ultraflex 2. I skim coated the upper portion of the CBU with drywall compound to ready it for texture and paint. For the fun part, I finally installed the tile. Argentina porcelain tile - looks like travertine, but it's not! Man! What a lot of work, but finally a bit of progress. I still need to tile the bull nose around the edges and then on to the floor.

I can’t leave tonight without one question. One of the trim pieces around the niche lost its place and the grout line is crooked. What are the tricks to fix that? I thought of a dremmal tool to chamfer the edge to make it look like the grout line is straight?

Hope you all enjoy the pichers. :clap1:

11-28-2006, 11:01 PM
Ya know, there gotta be a auto-reformat-the-picher-to-fit-the-super-restrictive-requirement-for-photo-upload-configure-for-me forum function!

John Bridge
11-29-2006, 07:29 PM
Lookin' good, Tom. :)

11-29-2006, 07:35 PM
Yeah, I was meanin' to talk to you about that one picher there in that first group. :rolleyes:

But the shower is lookin' good. :)

12-11-2006, 12:36 PM
I found out my brother and his family are coming out after Christmas. Nothing like a deadline to get you motivated to finish a project!

Progress to date:
I finished off all the trim pieces and niche in the shower. I installed 1/4" hardibacker on the floor using Ultraflex 2, screwed it in place every 8" and around the corners. I left 1/8" to 1/4" space between the boards and around the walls and taped/thinset the joints. I installed the porcelain floor tile as shown. Floors are sooo much easier!

I am looking at Koehler and Basco framelss shower doors. Are these a good options or should I look at another company?

12-11-2006, 01:12 PM

Like mine was, that pretty new shower of yours is calling, no - screaming, for a glass door.

I used Wilson Glass. Great price, good folk.