# reapplying mortar to bond Ditra to Hardi Backer Board



## Tim Bingham (Jun 2, 2009)

I am remodeling my master bathroom and creating more shower room. I have already expanded my area and constructed it. I have covered the framing with 1/4 inch plywood and topped that with 1/4 inch backerboard in the entire area. I know I can tile directly onto the backer board but I added a final layer of ditra to ensure more water proofing (mainly because I don't trust my work in my own home). I just put on a layer of ditra on the back wall of the shower but I believe the thin set dried before I could get it to bond correctly. If this is the case and I have to remove the area of ditra that has not bonded. 

Do I just ensure the already applied thin set mortar is scraped level and re-apply a thicker coat of mortar to ensure bonding and reapply the ditra again?

What is the best method of applying dirta to walls to ensure bonding has taken and tile is ready for application?

Tim


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## jerryh3 (Dec 10, 2007)

Ditra on the walls? I hope you mean Kerdi. I my opinion everything about this install is wrong. You should have used 1/2" backer board on the walls topped with a waterproofing membrane. Where did you get the 1/4" plus 1/4" idea?


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## Ron6519 (Mar 28, 2007)

Where in earth did you get this information on tile substrates? Got to agree with Jerry on this. 
What type of thinset did you use to apply the ditra? Modified or unmodified?
Ron


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## Tim Bingham (Jun 2, 2009)

Ron and Jerry,

First of all thanks for responding, but why would you say everything is wrong about this project, because I didn't use 1/2 inch backerboard on the walls? and Ditra as oppose to Kerdi?

Doesn't 1/4 inch plus 1/4 inch equal 1/2 inch strength and limits movement still the same as 1/2 inch backerboard and adding Ditra lessens movement more. 

Is there a difference in using Ditra as oppose to Kerdi on the walls, have you never used Ditra on the walls or seen it done, what is the huge problem with this?

Again the questions I pose to simplify matters are:

How much time has to pass before Versa-Bond Modified mortar solidifies and Ditra becomes null and void to add to the walls? 

What is the best method of applying dirta to walls to ensure bonding has taken and tile is ready for application?


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## jerryh3 (Dec 10, 2007)

How did you attach the backer board to the plywood? No, I have never seen Ditra used on a wall before. And, actually the ditra will not "strengthen" the assembly. It's an isolation/uncoupling layer used to isolate the tile/substrate layer.


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## Ron6519 (Mar 28, 2007)

Tim Bingham said:


> Ron and Jerry,
> 
> First of all thanks for responding, but why would you say everything is wrong about this project, because I didn't use 1/2 inch backerboard on the walls? and Ditra as oppose to Kerdi?
> 
> ...


I just got off the phone with a Shluter rep who was a little surprised with the question about Ditra on the walls.
He said he guesses you could put it on the walls, but doesn't know why you would.
You realize that just putting Ditra on the walls will not waterproof the installation.
To apply Ditra, you would use an unmodified thinset, not what you were using. They recommend not using a latex modified thinset.
The thinset needs to be on the loose side to install the Shluter products. Whether it's Ditra or kerdi.
Ron


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## Tim Bingham (Jun 2, 2009)

Jerry and Ron, again thanks for responding, the framing installed goes as follows:

1/4 inch plywood to the studs and 1/4 inch backer board nailed over the plywood. all nails were counter sunk and about six to eight inches apart. 

Currently I'm applying Ditra to the backerboard to add for waterpoofing and more stability or lessening the movement so grout and tiles do not crack or break if someone leans against the wall or decides to sit on the bench I installed. I realize installing Ditra does not waterproof it but more is better than less. 

The floor is a concrete slab and not Ditra is going on the floor; I will will tile directly to the concrete floor and the new pitched concrete floor inside the shower area. 

Again my question is how much time has to pass before versa bond solidifies and bonding is ineffective. This allows me to determine the sizes of Ditra sections to install and avoid ineffective installations. 

Does anyone know this answer, or is it trial by error based on the mix of the mortar; or is there an average time? 

Is it OK to mortar over freshly dried mortar to reapply Ditra?

Tim


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## Ron6519 (Mar 28, 2007)

As far as I'm concerned, you're on your own with this incorrect installation. 
Ron


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## jerryh3 (Dec 10, 2007)

There should be a cure time on the bag. If you scraped it thin when you took off the Ditra, it should dry out quickly.


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## Tim Bingham (Jun 2, 2009)

Ok Ron though you never did tell me why it is all wrong, I guess you have never done it this way maybe that's why. I appreciate you weighing in on my post thanks anyway.

Jerry it dried to fast for me to get it completely scraped, so can one mortar over existing mortar? Im attempting to flush the surface. 

What would be a way to correct this?


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