I'm building a very small bathroom, similar to some I have seen in Scandinavia, where the shower, sink and toilet all share the same pan. Finished floor size to be 32 x 52 inches. To top it off, I want to include hydronic heating.

Here's the plan for the pan from bottom to top:

Hydronic Floor - Built up with 3/8" PEX on 4 inch centers.
1 - 1/4 inch HardieBacker
2 - 1/2 inch Durock + PEX
3 - 1/4 inch HardiBacker

Roofing Felt

Tile Base sub pan with acrylic modifier

CPE membrane

Tile Base pan with acrylic modifier

Topped with thin stone tiles and modified sanded grout.

Any feedback?

I understand the principle of the three-part shower flange, with weep holes, etc.

I am stuck, however on the toilet flange. The toilet flange will be half way up the pan gradient, and only 23 inches from the shower drain. I have not been able to find a three piece toilet flange, but I have a metal lathe and can turn one from brass.

I really need feedback on this one... Is this something I need to do?

Also, will the layer of roofing felt allow for thermal expansion?

Here's a photo of the layout.



The shower drain is roughed in, as is toilet. Sink is upside down to give an idea of size & placement.

Regards,

-gnu_B

Your photo does not work as posted. Go to the section of the forum for posting photos and place it there.

Your plan seems rather confusing at this point with all the under layment layers.

RC,

Thank you for your reply.

I have re-posted a photo HERE. This time, it looks like it's working...

"Confusing" huh? Well that about sums it up. I have been reading books (some very good) and scouring web sites (this one especially good) and getting advice from friends with no tile experience at all (very bad), so it's probably natural that I'd be confused.

So, what I'm trying to accomplish is a very small wetroom with a hydronicly heated floor. I have been reading so much about floor movement and grout and tile cracking and isolation layers and thermal transfer, de-coupling etc. that I'm starting to dream about this stuff.

After looking over this website, I maybe should have posted to a few different areas, but it seems that all of this works together and the obvious expertise in this topic area regarding the managment of expansion and contraction really got my attention.

What seems like the biggest 'gotcha' to me is the toilet flange issue, as I mentioned previously.

So far I'm not too committed to any particular technique, with the exception being that I did get enough CPE membrane material for the job. I'd also like to do hydronic heating instead of electric resistance mats in the floor, for the sake of energy efficiency.

Best Regards,

-gnu_B

Total Score today!

I found a recycled window that had been custom made, but to the wrong dimensions for the original owner. It is Low-E, Argon-filled, Energy-star, too.

I wanted a tall, narrow double-hung to go in the exterior wall behind the toilet.

I was fully prepared to pay over $250 for one, but then came up with this ruby for only $34, and it's just the size I wanted.

What is the purpose of the three layers of CBU?

It's the best way I can think of to build up a hydronic floor and keep the height a low as possible. I've done somewhat crude thermal transfer tests on various materials, and Durock and HardyBacker come out looking pretty good. My idea is to use the lowest 1/4" HardyBacker as the foundation, the next 1/2" Durock cut in strips, with PEX in between, and thinset around the PEX to improve thermal transfer, and another 1/4 inch of Durock on top. Kind of like a thermal sandwich, all bound together with thinset.

In the tests I did, If the concrete mass is thin, there were pretty large differences in temperature across the surface of the concrete, but when tubing was spaced closer, the differences in temperature were minimized.

I know of people making built up hydronic floors out of High Density particle board. Concrete board is a better conductor.

A I write this, I realize that my built up 'sandwich' is an inch thick, and if I just put the Pex on the underpayment, and poured concrete directly over the Pex, it would be thinner.

I guess all the layers and tar paper is also an effort to reduce cracking due to temperature changes.

Regards,

-gnu_B

If you haven't already done so, take a look at this web page of Harry's. While he's using heating cables instead of tubing, I think the principle may be the same. This might give you some ideas of how to incorporate a heated floor to your project.

http://www.ontariotile.com/heated-showers.html

Yeah, the electric floor heat sure looks a lot simpler.

Say, I saw something mentioned on a UK blog regarding the number of CBU fasteners required per square meter, to properly support the weight of the CBU and the additional weight of the tiles. Is there any similar spec or rule of thumb on this side of the pond?

Also, I initially bought some PVC membrane material. But then I read this affidavit from the Neew York Attorney General...
http://www.healthybuilding.net/pvc/NYS_vinyl_affidavit_js.pdf

I have since then purchased CPE for the same purpose.

Is there concern in the Tile Setting trade about the use of PVC?

Regards,

-gnu_B