Best Tile underlayment [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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07-01-2002, 04:49 PM
I'm a very novice tile layer(a couple of small projects is all) and I'm getting ready to tile about 600 square feet of floor in a new home I'm building. I've used Duroc before and wasn't overly impressed. What is the best backer board/underlayment for a novice tile layer for use on a 5/8" plywood subfloor over 16" O.C. Joists over a basement? Are Hardibacker or Denshield any good? I've heard good things about Ditra, is it worth the added cost?

Much thanks for any help.

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Rob Z
07-01-2002, 05:46 PM
Hello, and welcome to the forum

I now use Ditra on all floors that don't get floated with mud. Many of the other guys around here are partial to it, too.

I think it is a well designed product with a good track record. Ordering by the roll should make it quite cost effective. If I had to drive nails over 600 feet of cement board, I would give up.

The analysis of whether ditra is OK for you sitution depends on many things, including joist size and span. Let's start with those measurements.

07-01-2002, 05:56 PM
Ditra hmmmmmm Oh Andy, Andy Acker, where are you,call me please so i can shame you (rob told me too) :D

John Bridge
07-01-2002, 06:03 PM
Hi RJ, Welcome.

I can't add much at this point. I'll wait for the answers to Rob's questions. I will say I'm sold on Ditra.

Hey Todd,

Maybe we're gonna hafta go to the top. Let's email Herr Schluter! :D

Ich kann klein Deutsch sprechen.

07-01-2002, 07:32 PM
Well, I'm a novice tile setter and I love the ditra. I have used the hardi-backer before, but prefer the Ditra anyday over the durock.


Mike Berry
07-02-2002, 01:03 AM
Has anybody heard of or used 1/2" Denshield?? If so, whats the opinion for using as tile underlayment in 10' x 5' bathroom floor over 3/4" exterior plywood subfloor? Also, what kind of underlayment is ditra?

07-02-2002, 05:24 AM
The ditra is nice for the bathroom. It can be use as a waterproof membrane as well. If all you have to do is a 10 x 5 area, you may not be able to justify buying a whole roll.
You can request a sample of ditra from the mfgr. You can carry a whole roll of ditra (330 square feet) easily with two hands. The tile bonds to a plastic like grid and the underside of the ditra has a felt like texture, this bonds to the floor. (see their website

Never used denshield.


John Bridge
07-02-2002, 06:14 AM
Denshield is garbage. Ditra can be found at

07-02-2002, 08:05 AM
Thanks for the input about Denshield. I considered using it but began doubting it's capability and that's what led to my question here in the Forum. I have now forgotten it and am weighing out Ditra, Duroc, or Hardibacker.

Rob and John,
The joists are on 16" centers and are 11 7/8" TJI/Pro-130. The 500 feet of tile on this floor will span from the front of the home(entry) to the rear of the home (hall way, kitchen and nook) for a length of 34 feet. It will also cross the beam supporting the first floor (above the basement) wich will run at the midpoint of the 34 feet. What are your thoughts?

Thanks again for all the good comments.

John Bridge
07-02-2002, 04:54 PM
I'll let Rob pronounce on the subfloor. Or Bud, or Bri, or anybody. :)

Seems like it ought to be stout, though.

Rob Z
07-02-2002, 07:53 PM

Have you performed the patented John Bridge Bounce Test?

(How bouncy does that floor feel when you jump on it?)

07-02-2002, 08:31 PM
I hadn't heard about that test, must be a trade secret? - but one that would take an expert touch, best left to the professionals? Unless in an email you can instruct on the finer points?

I went to the Ditra web site and looked at their recommendations and the floor appears to meet them. Any reason why Ditra wouldn't work? or any potential problems with Duroc?

Herb H
07-02-2002, 09:50 PM
Hey ya all, I posted a like question about Durock and modified thinset vs non-modified thinset, and got the recommendation to use Utilicrete as a better product. No mention of "I now use Ditra on all floors that don't get floated with mud."

First day working my butt off putting down 1/2" cement board when I could have used something better and easier??? What about the 1 1/8" rule for subfloor?? Is 5/8" and Ditra ok???

Just got home had couple beers, dog tired, turned on computer, went to favorite place for easy reading and am now bummed out.

Rob Z
07-02-2002, 09:57 PM
Easy now Herb...

When asked which backer board is the best, I respond with the recommendation of Utilicrete. (I've put in a lot of cbu from the big three-Utilicrete, Durock, and Wonderboard).

Did you ask for a recommendation of which CBU is best, or did you ask if Ditra was superior to CBU?

07-02-2002, 10:03 PM
Rob, Nice Spin:D

Herb, Have a couple more beers :D

John Bridge
07-03-2002, 06:16 AM
You done good, Herb. Kick back. :D

Hope you know by now there are no concrete answers around here, because there are no concrete answers in our trade. Through the course of time we almost reach consensus on minor issues, but the big stuff eludes us.

Hang in there, buddy. ;)

Herb H
07-03-2002, 04:40 PM
Hi ya all,
Taking it easy, took KW's advice, mo beers. Now that was solid advice. Doing better today. That cement board is some nasty stuff. When they loaded it onto my trailer the guys fork truck had short forks and couldn't get it up over the wheels, damm stuff (full skid 50 sheets) tried to lift my Tahoe off the ground. Hand carrying a full roll of Ditra sounds better.

Floor does feel a lot more solid with 1/2" cbu. Think this is going to work out, unless nasty cbu tries to put the first floor in the basement. Thanks to all of you for taking the time to respond to us rookies out here. My first day at it yesterday, I have an idea how tired you must be after a full day of this kind of work, then take your time to help us. THANK YOU, THANK YOU.

John Bridge
07-03-2002, 04:48 PM
Don't be a stranger, Herb. Keep us posted.

Bud Cline
07-04-2002, 12:21 AM
We eat Wheaties daily.

Herb H
07-13-2002, 11:06 PM
All I really wanted to do was to put down a few hundred feet of tile and not screw it up. But nooooooo not me, had to make it complicated. Modified Vs non modified thinset, Durock Vs Kedri, Ultracrete Vs Durock, Durock info. "Laminate Durock Brand Underlayment to subfloor using ceramic tile mastic, latex-fortified mortar or thin-set mortar mixed with acrylic latex additive applied to subfloor with 1/4" square-notched trowel for thin set, 5/32 V-notched trowel for mastic." (MASTIC WHAT THE HELL) Everyone said follow manufactures advice. So here I am almost all 50 sheets of Durock down with Versabond sticking it to the subfloor and roofing nails keeping it from squishing around. Now the last couple day's posts everyone is coming out of the closet and saying use cheap non-modified thinset. What's a guy to do??? Am I going to survive this ???? Is the Versabond good enough to stick the 12" tile to the Durock ???? Can't go back now !!!
Herb, Give me lotsa mo beers

Herb H
07-13-2002, 11:21 PM
Forgot to tell ya all about first bucket of Versabond. I put two quarts of water in a 5 gal. bucket then added some mortar, stuck this big mixer attached to my 1/2" drill and hit the trigger(not enough mortar too much water),it exploded out the bucket coated me, garage and friend. Failed mortar mixing 101.

Rob Z
07-14-2002, 07:51 AM
Hey Herb, don't mix it that way :)

Don't lose too much sleep over the thinset under the board thing. I put in a lot of cement board with the "wrong" thinset before I knew the difference. All of us probably have.

This is a topic that is not so clear cut that everyone can reach the same conclusion.

John Bridge
07-14-2002, 12:02 PM

Aside from spending a little extra money for the Versa Bond, which is good stuff, you haven't done any damage.

Mo beer.


As far as manufacturers instructions are concerned, I think it's a sin. All of them are card carrying members of the Tile Council, and yet they put out info that is contradictory to that adhered to by the Tile Council.

Don't get me started on this. Dave G. will have to come in and try to justify it again. :D

Herb H
07-14-2002, 09:09 PM
Great day today, last bit of Durock is set. Now about sticking tile to Durock. Is the Versa Bond ok or do I need to upgrade a level? Got 12" tile going down.

This is hard work, but probably putting me in better shape than I have been in for years. Thanks for the guidance.


John Bridge
07-15-2002, 06:06 AM
Versa Bond is what I use. I'm a Home Depot type guy. ;)

07-15-2002, 06:38 AM
John, I thought we were sposed to watch our language in here??? :D

Herb H
07-15-2002, 09:05 AM
Thanks John,
Versa Bond it is then, besides that now have a good feel for mixing it.

07-15-2002, 02:37 PM
Well, thanks for all your comments. I have greatly appreciated the site.

I am now nearly complete with the 650 square feet of floor tile (many long evenings as I've been unable to take time off work!). I decided to use Ditra and have been happy with it so far. I was able to lay down all of it in a day and a half - so for me it was well worth the cost.

I also need to correct my previous statement- the floor is 3/4" OSB and not 5/8" plywood.

John Bridge
07-15-2002, 03:26 PM
Hi RJ, Herb sorta stole your thread, didn't he? :)

Schluter warrants the Ditra over OSB, so if you've followed directions you should have a fine installation. 650 feet is a lot of tile even for a pro. We haven't discussed movement joints and perhaps we should. It's a big field you have.

Herb H
07-15-2002, 08:49 PM
Hi RJ, sorry for being so windy on your thread. As you can tell I am doing a job about the size of yours. Sounds like you took the better road using Ditra. After reading your last post (650 sq.ft. in day and a half) if I do another project you can bet I will use it. Will be interesting to hear what John has to say about "movement joints". Smooth grouting to ya.


07-17-2002, 08:04 AM
When I posted yesterday I was in a hurry and didnt't notice the thread continued onto a second page! So I just now caught up with your project. Good Luck.

I thought about expansion joints as well, but haven't put any in. Is that going to be a problem? I'm putting in 650 square feet but 150 square feet are in two separate baths. The other 500 square feet wind around through an entry, hall, 1/2 bath, kitchen, pantry, nook, and mudroom (a lot of cut tiles! - I completely underestimated what it would take to cut that many). Reading in a book I have it was unclear whether I needed an expansion joint and I certainly couldn't tell where I'd need one if I did. The hall does run into the kitchen so there is one long length of 34 feet, the next longest length is 20 feet.

Bud Cline
07-17-2002, 10:55 AM
If you allow a 1/4" gap at all wall junctures and undercut all jambs and casings to allow the tile to tuck-under those areas then the only concern is the 34 foot length.

You could do a 'soft joint' across the hallway door opening to reduce the 34 feet to the width/length of the kitchen.

I think your in good shape but a floorplan posted here would be helpful.