How high can we go? [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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08-21-2004, 03:53 PM
A funny thing happened on the way to finishing our bathroom floor. It just occured to us that we may end up with a much higher floor than what we can match up to the bedroom carpet. :uhh:

Here's how many inches we anticipate adding to the plywood subfloor:

Thinset / CBU 0.25 +
SLC over Nuheat mat 0.50 +
Thinset / Ditra mat 0.25 +
Thinset / tile 0.25 +

TOTAL floor height increase 1.25 + (minimum)

We're considering the Schluter Reno-V or Reno-U in the doorways but don't know how much of a height difference they will accomodate.

Is it normal for a tile on radiant heat application to add this much height to a floor? :confused:

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Rd Tile
08-21-2004, 06:37 PM
Maybe someone else can add to this, I don't use Ditra, but it seems to me you have too many substrates here together, CBU, SLC and Ditra, I would say all you need is one or the other, all can be tiled over.:)

08-21-2004, 07:40 PM
According to Nuheat's installation instructions the Nuheat mat is to be thinsetted to the subfloor with modified thinset. After that tile can be applied with thinset directly to the Nuheat mat.

So, I don't think you need quite so many layers either. The Pros will want to know your flooring structure - Joists, Span, Subfloor material, etc.

Forgot - Nuheat Instructions (

John Bridge
08-21-2004, 08:14 PM
Hi Laura,

I don't know diddly about infloor heating. Hang tight. ;)

08-21-2004, 08:15 PM
We have a 3/4" plywood subfloor on 16" center I-joists. We've already laid and taped the CBU. Photo to follow. Now I'm worried. :(

08-21-2004, 08:23 PM
Picture for those that don't want to mess with the Adobe Reader (pdf)...

08-21-2004, 08:26 PM
How did you do that, Joe?

08-21-2004, 08:32 PM
Well I opened your pdf file in Acrobat, and then captured the image into PaintShopPro. A quick little resizing to make it fit into the forum and attached it.

John was kind enough to post my "how to resize images" tutorial in the Liberry. Check it out when you get a chance.

BTW, I think you can probably install the nuheat over your CBU and then tile directly over the nuheat as per their instructions. Now, if your floor still needs some leveling, that's another story! Definitely wait for some truly expert advice though.

PS - I really like your tagline.

John Bridge
08-22-2004, 07:33 AM
I don't have to be an expert to know that Joe is correct. I've read the directions :D , and you can install your tiles directly over the mat. Also, your estimates of the various thin set layer heights is a bit strong. Thin set does not consume that much space. Applying thin set with a quarter-inch notch trowl will result in a bed that is less than an eighth-inch in height once the tile or other product is forced into it.

08-22-2004, 10:17 AM
Okay. It sounds like we can eliminate the SLC and Ditra mat. I really did read Nuheat's instructions but assumed they represent minimum requirements and are primarily concerned with the Nuheat product, not the finished tile surface. Somewhere along the line I got the impression that using SLC and/or Ditra may be necessary to achieve a smooth surface for laying the tile, especially for a first time DIYer. I'm still a bit concerned about making a smooth transition from an area with the Nuheat mat to an area without the Nuheat mat but I assume we can accomplish that with thinset.

Thank you for your help. :)

08-22-2004, 10:35 AM
I have said a time or two that I install Ditra over the wires but this is over a slab where cracks could be a problem. I wouldn't think you need the Ditra along with the CBU. They show tiling right over the wires but they don't show any chalk lines on the floor, just setting the tile by eye. I've got to have lines myself, guess you would need to pop lines before laying down the wires. I like to put a thinset coat just to hold down the wires but thinset isn't very easy to work with, that's why SLC was mentioned.

You can build up under the carpet at the doorway with wood shingles or patching compound. 1/2 inch build up is hardly noticeable.

08-22-2004, 12:19 PM
Laura, Self Leveling Cement is no longer an option anyways.
You need a 2 layer wood subfloor.Plywood would have had to have been used rather than CBU for an SLC pour.
All that typing for naught :cry: