I hear here lots of talk about Ditra underlayment,I have never worked with it,always used hardi backer.

 

First off , the subsrate needs to meet the required live and dead loads.
(ie: l/360 or 720 for stone)If that is met you can use a few differant systems.
I vote for Nobleseal bonded down with Noblebond.(but I'm a Noble guy):jester:

 

Like Eric said, deflection concerns first then a membrane. I use Ditra.

 

I'm nailing down the 3/4 osb with ring shank screws and I use plenty of adhesive. I put in solid wood blocking at half the span, screwed in. The blocking which comes out goes back in horizontally under heat runs, etc.

I install denshield with thinset and roofing nails. No problems. As far as spans, I just use the span tables (16" OC lets me use 2x8's for 12', 2x10's for 16'). The blocking is not in the span charts, etc. but I know it helps a lot. Also makes me more comfortable when I'm installing the osb.

 

It seems like there is some screwy laws when it comes to ditra on osb... I thinset down durrock or hardie and nail for prep... I'm also looking into Noble TS but waiting for a PM back from Eric :whistling:

 

What screwy laws are you talking about Dawg? I know Angus has a problem with Ditra over OSB, but Herr Schluter doesn't.

I've laid literally thousands of feet of Ditra over OSB, never a problem. :thumbsup:

 

Good to know! I guess Angus is a bit on the picky side..... :laughing:

 

My question was about thinset manufacturers. On most bags, it says OSB is not an acceptable substrate.

It was explained that particular instruction was for tiling directly onto OSB.

I still prefer to not lay a membrane over OSB.

Since Eric is chiming in, what say he about the subject??

 

My question was about thinset manufacturers. On most bags, it says OSB is not an acceptable substrate.

It was explained that particular instruction was for tiling directly onto OSB.

I still prefer to not lay a membrane over OSB.

Since Eric is chiming in, what say he about the subject??

That's y I said that... I have yet to find a thinset that states its ok to use over osb... makes me uncomfortable

 

I hate OSB and would not bond anything to it but more plywood. If a floor has OSB the chances are that it is built to the bare minimum and only has a deflection rating of L/320.

With a bouncy floor like that I would add in solid blocking on 4' centers and another layer of 1/2" to 5/8" plywood to stiffen the floor assembly to L/720.

I have installed rolls and rolls of Ditra with no problems - in the past few months my new love is Nobel TS. I like the fact that it is flatter than Ditra and from what I understand out preforms Ditra as well....

JW

 

I'm not sure how "chances are" an OSB subfloor means the joist structure is built to minimum standards. I honestly don't know where you come up with this stuff John. :w00t:

We all know solid blocking can make a floor "feel"more solid, but from an engineering standpoint, it does nothing to improve the deflection ratio.

 

I don't like OSB. I do renovations and have seen what it can look like after some moisture gets to it

 

If the framing is suitable then I put plywood over the osb and tile.

 

what we put down for a subfloor depends on the budget. on higher end jobs we use 3/4" plywood otherwise osb. the only thing that changes is that on osb subfloors we use pl with teh ring nailer for putting down underlay. we use 3/8 doug fir for our underlay, tried durock on the floor but had issues with tile pops. if its a reno where the subfloor is boards we up the underlay to 1/2" for a bit more strength.


our tile guy never uses deitre mat, but he does use the waterproofing. never had an issue with his work other than small detail stuff. no tile pops or anything

 

If you had issues with CBU it was likely due to installer error. Plywood is one of the worst underlayments to use for tile.

 

Years ago a thinset manufacture said you could use the product on luan plywood (that was the underlayment in use at the time). A tile shop started to use the material in midsize homes.The failures started just after the 1.5 year mark. The tile could be lifted off the plywood by hand. Thinset stuck to tile but not the plywood. The tile shop owner replaced 10-12 homes at his expense assuming he would be reimbursed by the manufacturer. When they refused to pay him, he lost the business. I was hired by the new owner, his previous estimator.

I installed 1200' of laminate in a basement. The original install was glue together material. A sump pump failure required replacing the entire floor. By then, the manufacturer had switched to click together material. The floor was installed according to their specs. About 3 months later, I get a call from the owner saying the seams are peaking. I look and he's right. So I call a manufacturers rep and he comes out. He investigates and has a piece of flooring shipped to their lab. The report clears me of any wrong doing. (I suspect the cleaning people were wet mopping the floor). Case closed.

Take the chances your comfortable with or can afford to replace.

 

I have ripped up many a floor with 1/2" plywood as the tile substrate over 5/8" sheathing.

1/2" cement board over 5/8" plywood is often frowned upon as the cement board offers up no rigidity to the floor assembly. 1/2" plywood over 5/8" sheathing and then Ditra, Nobel TS or 1/4 cement board makes for a tank of a floor.

Most large format tile and natural stone will call for 5/8" plywood plus 5/8" plywood and then the setting materials and selection. It's the thickness of the subfloor in wood that is the common point in the various tech manuals.

Most times here in Vancouver we pull up the entire subfloor (with in reason) and cross block the entire area. New 5/8" plywood. New 1/2" plywood and then we go with cement board or Ditra. Of late I have stop using Schluter's products all together and have switched to Nobel TS as my go to product of choice.

If a floor was not being heated I would be banging down 1/4" cement board with nails and thinset.

I have read online that 1/2" cement board offers up no deflection improvement on a floor assembly but find this hard to believe.

I have read online that solid blocking offers up no deflection improvement and find this even harder to believe after 20 plus years of renovations and many projects with structural engineers.

The simple fact that 90 plus percent of all homes build in North America are build to a deflection critieria of L/360. Off course in many areas the floors will be stronger but the large open areas will be this L/360.

I joists are designed to this L/360 in most cases. Look up the various manufactures and you will even see these numbers in their product names 360. 480. 720 etc...

If a floor will flex you will have popping tile and cracking grout. Does it flex with just you under foot or does it take a house party to tip the scales? After my last two Mapei training classes we will start measuring these deflection rates before going forward with repairs and try and put out some sort of "Second opinion" on this whole cross blocking debate.

Mapei recommends an engineer to preform these tests for their larger commercial jobs. In my own home here in North Vancouver some missing Strong Tie hold downs have lead to two triple 2"x10" beams pushing up on my double 5/8" plywood floor. Pushing up to the point of 3/16" out of wack.

A thousand things can cause floor failure. Point Loads. Sagging beams. Settling foundations and on and on. In my opinion you need to "Feel" this underfoot and look for every possible scenerio.

I even read somewhere on line that Ditra can be laid straight over old ship lap floors.... anyone trying this at home would be crazy in my opinion. And how many floors have you seen installed with 1/4" OSB and some staples as the tile prep?

If I see OSB as the subfloor I assume straight away we are built to the lowest possible deflection criteria. Proceed with caution and stiffen the "*****" up...

JW

 

Wow, took me 10 minutes to read, but some good points! Thanks John!

 

Wow, took me 10 minutes to read, but some good points! Thanks John!

If you have a Mac, you could turn on the Universal Access feature, and have it read to you instead, taking about two minutes or so for the above post.

 

I can read, if that's what u were wondering *eye roll*

 

Not at all.
In fact, I work alone 75% of the time, and that allows me to rock the ipod for podcasts while I work.

Long story short, I heard about listening to podcsts on 2X playback speed from another forum, and as crazy as it sounds, it's easy to understand, and really keeps me moving. For example, http://borntofarm.com/category/growing-your-grub/
was interesting, but unlistenable to me based on his slow delivery. Now, I can't wait for his next episode.

Just trying to share tech tips, as I love the way info flows nowadays.

 

just curious about this nobel product always used ditra or cemnt board any pictures or site one can go to? and whats the cost differences

 

http://www.noblecompany.com/

NobleSeal TS is about 5-10% more than Ditra; depending on your supplier pricing.