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Jn5685 01-20-2013 10:17 PM

How to build a shower after bathtub removal?
Ive been researching for about 4 months now on how to replace my one piece fiberglass bathtub with a tiled shower stall. I have begun this project today. I have removed the tub and bathroom flooring so far. The tub was installed over the concrete slab. I am confused now since I saw the slab was cut around the drain at some point in the houses 27 year life. Its not a smooth or even cut either. It was filled with sand. Is this normal?

My question is: since the slab is cut aroud the drain and water pipes how do I build the shower the pan? Would I use 2x4's on the slab and plywood over that and moisture barrier and then mud, or fill in the whole with mud and go from there? Looking at the area, the drain is to the left. Should I center the drain or get a sloping kit and leave the drain where it is. It seems like it may be easier to add a plywood floor over 2x4's to allow room to run the drain piping.

The tubs over fill and drain hole appear to be one copper piece. It looks like it is secured to PVC with some sort of pressure fitting which is below the top of the concrete slab. It is accessible since it is surrounded by the sand.

Alan 01-20-2013 10:24 PM

First of all, you're in for a surprise : Your tub was likely plumbed with an 1-1/2" drain. Your shower will require a 2" drain or it will not operate properly.

That said, now you're in for a jack - hammering job and you may as well reroute the line to the center and do it right.

Let's get that step out of the way first, then we'll worry about shower pan buildup. ohmike has some links bookmarked that I haven't bothered bookmarking (maybe this time I will) but i'm sure he'll be along shortly to share with us. :)

joecaption 01-20-2013 10:27 PM

And you did get a permit for this right?
Yes there was suppost to be sand around the drain to support it but allow some room for expantion and contraction, some people add a skim coat of morter over it.

No big deal because your going to have to bust out some of the concrete anyway because a shower has to have a 2" drain, tubs use a 1-1/2 drain.

No plywood is never used to form the slope!

Really need to post some pictures so we can see what your seeing.

Jn5685 01-20-2013 10:46 PM

How far back usually and what exactly am I going to trace the drain pipe to? The main drain under the slab is 1 1/2, just measured it. The bathroom has 1 sink and 1 toilet. It backs up to the other bathroom in my house. Can someone tell me how to upload pictures from an Iphone, I just took some.

Jn5685 01-20-2013 10:54 PM

I forgot to ask in my last post: why does a shower need a larger drain than a tub? Im not saying anyone is wrong, just want to learn. All the researching I dis online never metioned anything about swapping drain pipes for larger ones

TheEplumber 01-20-2013 11:30 PM

199 Attachment(s)
Most, if not all plumbing codes require 2"
You'll need to follow the 1.5" back to where it ties into a larger drain.
As for the iphone- mine downloads to a file on my PC. Then I upload it to the forum. Check the sticky's here-

Jn5685 01-20-2013 11:50 PM

4 Attachment(s)
I understand that code calls for the 2 inch pipe. I just want to understand why this is. I GOOGLED it after the first post and found several answers from several forums. Nothing certain though. One answer was given because more hair will be clogged up because a shower drain has a larger strainer. One response I saw said because a shower drain is centered and will have more tendacy to be stepped on and clogged by a foot. Really? Come on. If it is just because of code then I understand. I am not sure I really agree with more of a chance of clogging because my old tub's drain had no cap, strainer, or anything. Just a chrome hole in the tub.

One reply I did seem to agree with was that a tub drain has the over fill vent. If this is the case, couldnt I just incorporate a new vented tub drain in my construction?

Pics should upload with this post.

Jn5685 01-20-2013 11:53 PM

1 Attachment(s)
I forgot one picture. Looking at the picture that has the yellow broom in it, to the right, behind the toilet is a large PVC pipe behind the wall. This pipe runs up into the attic and out the roof. Would I be safe to think that this would be the area that my current 1-1/2 drain pipe is ending up? Its right around 59-65 inches from the current drain hole.

joecaption 01-21-2013 12:00 AM

Waste of time to try and understand this one and just except it and move on.
It's been code for many years. The people that write the codes do not just get paid to come up with stuff.
More then likly it's so the water will go down the drain fast enough so your not standing in water waiting for it to drain.
What do you plan on using to cover the walls?
I can not think of anything in a bathroom where you would use plywood on the wall.

Jn5685 01-21-2013 12:25 AM

Guess Ill leave it alone and stop searching for the "Why" then. I am going to use cement board to cover the walls. The plywood I was referring to was in one of the "how to" videos I saw. Bassically you lay them out as floor joists and run the drain on top of the slab to where it needs to be (centered). Then you install tar paper and mesh. Then the mud. The the pan liner and more mud, also at this point you would set the slope. Then tile. Seemed easy enough. Had I known I would be busting cement to re run a drain pipe, I likely would have just replaced the bathtub with another one. Which at this point may not be a bad idea.

I will call Tuesday and see exactly what Louisiana code is. I also read that 1 1/2 is acceptable in a remodel, just not new construction.

Assuming my drainage and water pipes are all correct, how do I end up doing this shower pan?

joecaption 01-21-2013 12:34 AM

I already posted a link to a whole list of videos on how to do it.
Some of the ways you have been suggesting do this and sites you seem to have been looking at are ways that were done long ago and all failed.

Blondesense 01-21-2013 02:54 AM

If you are showering in a tub and the drain is slow, worst case scenario is you end up standing in some water until it finally drains.

If you are showering in a stand alone shower a slow drain could potentially overflow the curb and cause some major water damage.

A larger drain pipe would make this less likely to happen.

I don't know for sure this is the reason, but it is what I always assumed.

Perhaps someone else could correct me if I'm wrong.

Edited to add: There are also prefabricated fiberglass receptors made if you don't want to build a shower pan yourself.

oh'mike 01-21-2013 06:48 AM

How to build a shower - Building a shower pan with pre-sloped mortar bed, liner and curb.

This is the link that Alan was referring to--

I also suggest you check out--Hydroban by Latacrete And Schluter--Kerdi--

When building a pan --there are several methods of waterproofing----sloped membrane under the deck mud---like the link above---

Paint on membrane on top of the mud bed (and walls)

Fabric membrane over the walls and pan---

Hot mopped tar--(Popular in California and Arizona but not around here)

All work well when done right---all can fail if done wrong--

Alan 01-21-2013 09:30 AM


Originally Posted by Jn5685 (Post 1098402)
I will call Tuesday and see exactly what Louisiana code is. I also read that 1 1/2 is acceptable in a remodel, just not new construction.

Trust me. You want a 2" drain. I've seen a few situations where someone took a shortcut, and then their shower drain was slow, and asked me to snake it. The snake comes out clean every time. They just needed a bigger drain pipe.

No sense in going to all this trouble if it's not going to be done right.

BC Plumber 01-21-2013 11:30 AM

The system I always use when doing a custom shower:

The kit is a few hundred dollars but its pretty much bulletproof to prevent leaks and assembles fairly easy. Also, if your code says 2" (1.5" is fine in BC, Canada IF it's individually vented), just do 2" while you have the chance now. You already have everything exposed, don't take a shortcut before putting in a nice custom shower! You will most likely just end up kicking yourself later. Also check to see if you need a permit (which im sure you will) and get the permit!

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