# Ditra or Hardie to fix this?



## Panzer5 (Oct 21, 2008)

(*Ignore use of 'Kerdi' - I meant 'Ditra')

Got a sub floor with three different angles... (no longer level)

Home owner asked me to come out & retile her bathroom floor. She told us we could just tile over the existing tile if we wanted. I told her we might be able to do that using Ditra- but I wanted to wait until we'd pulled up some of the fixtures to see what the actual underlayment looked like. 

What we found was ceramic tile mastic-ed to lick-n-stic linoleum squares, which was glued (yep, not just the normal linoleum adhesive) over the original tile floor. I convinced her to let me take it back down to the original tile.

That floor is in bad shape. Two cracks across the entire width of the floor give the floor three different angles. (see pics)

I'm thinking the best way is to level the floor using 1/2 inch hardie over thinset (after we clean the tiles).* I figure this will give me a sufficient separation from those cracks to ensure a good installation.

Any support for just going over this base with Ditra?
(seems to me like this would just preserve the three angles...)


Thoughts?


* Can't just bust out the old floor completely & lay a new underlayment / float a bed. The HO wants to keep her nice big cast-iron & porcelain corner tub & the plumbers & I think we'd torque it if we tried to move it.


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## angus242 (Oct 20, 2007)

I'm sure you meant Ditra, not Kerdi. :blush:

I would not feel comfortable tiling over that mess. Regardless of the new underlayment you install, there's still gonna be movement under it. 1/2" CBU doesn't make any difference if the mastic tiles or linoleum start popping. Besides, mastic on floor tile is a no-no. 

I love it when a HO tells an installer how to do their job. :huh:
It's like they will keep interviewing contractors until they find one that agrees to do it the wrong way just so they can save money.

Can't you cut out the existing floor _to _the tub?


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## Panzer5 (Oct 21, 2008)

angus242 said:


> I'm sure you meant Ditra, not Kerdi. :blush:


D'OH!!!:wallbash: Yeah, that's what I meant... (I had the phone ringing non-stop as I dashed in to post this... ... brain fart.)



angus242 said:


> Can't you cut out the existing floor _to _the tub?


 
I'm going to do that at this point. There was so much plumbing imbedded in the floor's original mud-bed that needed to come out - that we've had to take out a third of the floor anyway. That happened yesterday (after I posted this). Gonna take a skill saw with diamond blade & cut to within an inch of the tub & then take out the rest.

BTW - re:


angus242 said:


> I would not feel comfortable tiling over that mess. Regardless of the new underlayment you install, there's still gonna be movement under it. 1/2" CBU doesn't make any difference if the mastic tiles or linoleum start popping. Besides, mastic on floor tile is a no-no.


I wasn't comfortable tiling over the mess either - which is why we took out the mastic tiles and linoleum (and also explains how we found out the underlying original mud-bedded tiles were in such bad shape). The top two pictures show the floor after we cleared up the mess shown in the last pic...

*What I was pondering was in a case where you can't take out the mud bed and you have serious cracking resulting in three different angles, whether DITRA :thumbsup::whistling is a sufficient crack isolation membrane to handle that - or whether it would be better just to lay 1/2 inch CBU over the old tiles & drive on. (I've only used Ditra on one other project - and that primarily because I had a join between old & new mortar that needed isolating.)*


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## angus242 (Oct 20, 2007)

Panzer5 said:


> What I was pondering was in a case where you can't take out the mud bed and you have serious cracking resulting in three different angles, whether _DITRA :thumbsup::whistling_ is a sufficient crack isolation membrane to handle that - or whether it would be better just to lay 1/2 inch CBU over the old tiles & drive on. (I've only used Ditra on one other project - and that primarily because I had a join between old & new mortar that needed isolating.)


Few things...
You say "serious cracking". What is the cause of that? I would want to address that instead of covering it up.
Cracking in 3 different angles. Do you mean all in plane? Any heaving and forgetaboutit. There is no product that I know of that will help vertical issues.
How would CBU better isolate cracking than Ditra? CBU is chemically (thinset) and mechanically (screws) attached. Any cracking from below is going to put stress on that CBU. 

So depending on the cause of the original cracks, I would say Ditra would be better although it's not a cure-all.


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## Panzer5 (Oct 21, 2008)

angus242 said:


> Cracking in 3 different angles. Do you mean all in plane?


Yeah, - instead of a single floor plane, three different planes now exist (tried to show that with the pics). The cracks run parallel to the joists - probably _at_ the joists, and extend from wall to wall (...probably: two disappear under the tub). The floor between each crack has it's own plane. They act like they're hinged, rather than lipping one another.

Good news is there's no similar cracking of the ceiling below.

I'll know more after I bust up the floor today.


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