radiant and other stuff [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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01-16-2003, 11:14 AM
OK, this is an amazing board.

I am a structural engineer by trade and I am new to tiling but I love to learn new things by doing them.
(I put my roof up (doesn't leak), build furniture, plastering, plumbing and wiring, .. Not injured yet)

For my new house addition, I am planning to tile 3 bathrooms, a 400 sq. ft kitchen, and a small laundry room using mud.

In my preparations:
I bought John's buck (royalty check coming soon..). I have looked through Mike Byrnes book too.
I bought a felker tm-75 saw.

I will be putting in hydronic 1/2" radiant tubing which is not covered in john's book but I did find some threads dealing with this.

My understanding is that the floor sandwich looks like this:

Ditra membrane
1/2" tubing
6 mil poly
3/4" plywood

Is this correct? What is the minimum thickness I can get away with in the mud layer above the tubing?

Other questions:

Do you advise beginners to mud the walls or use the cement backer board?

Can I mud 10x10 floor areas at a time and wet or roughen the joints between stints?


Scott Bollinger

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Cami A
01-16-2003, 11:39 AM
That's a fine sandwich you're building there, Scott. You'll love the radiant heat. :D

Someone will be along to answer all those questions. ;)

01-16-2003, 11:43 AM
there will be details for radiant heated floors, in the soon to be out 2003/2004 tca hand book. what ever membrane is used over the mud bed should be able to give you r-valuesfor their product. Both . www.noblecompany.com and www.schlutecr.com offer products.(noble also offers hydronic anti freeze)

01-16-2003, 11:48 AM
spaced out___ also details are currently in tca handbook detail-f-141-02

give a man a fish and he will eat for as day - teach him how to fish, and he will sit in the boat and drink beer all day!

John Bridge
01-16-2003, 11:57 AM
Welcome aboard, Scott. Thanks for the royalty. Patti is on her way to Walmart this very minute to spend it. ;)

Before I address your questions, I would also like to mention that with the droves of engineers who seem to arrive on these shores, we don't get many structural and civil types. Tried to snag a dirt guy who stopped by here but haven't heard from him since. :) My point (yes, there is one) is that our chief engineer, Bob Campbell (bbcamp) will be happy to meet you. :D

Mud is still the best way to go if you can afford the height, which is a problem usually. The minimum thickness for a mud floor is 3/4 in., but then you interrupt that mass with half-inch heating tubes, and what do you have? I would say in this instance that an inch and a quarter would be minimum, and more is better.

The usual way radiant heat is done around here is with products that can be nailed to the floor under the tubing and then some sort of fill between the tubes and then the membrane.

Yes, I do (and I did in the book) advise weekend warriors to do mud work, but only if they are up to it. It's a lot easier to build a shower from cement backer board or from Kerdi.

I would not recommend mudding your floor in segments. I would get plenty of help and do it in one session. On showers you can do a wall at a time as long as you complete the wall, but on floors, it's best to have a monolith.

01-16-2003, 12:52 PM
Hi, Scott!

Your floor strong enough? :D

02-06-2003, 01:47 PM
I am hoping to put the mud in tonight. I think I might need as much as 2 1/2" mud in one room to accomodate different floor heights.

I have 2x12 @ 16" spanning 12'. using 150 pcf for mortar and tile I get 31 psf deadload. Code is 40 psf liveload. total is say 75 psf.

I get total load deflection at L/800 and Live Load deflection at L/1650 which should be good. I just bought a roll of ditra at depot, so I should be all set.