I'm not going to say it's wrong - and I'm not a professional tile layer. But I did a lot of research when planning my 2 marble bathroom floors and used Ditra on both.

My 2nd floor bath has 3/4 ply glued/screwed to the joists, and then a special 9 ply Russian birch 3/8" ply screwed just to the 3/4" ply, not 'through' with about 1000 randomly placed 1" screws in the 80 sq ft. The 3/8 Russian ply is purportedly as strong as 5/8" normal ply.

Anyhow - then thinset with Nuheat cables, then Ditra, then white thinset / marble 12x12 marble tile. Hasn't shown a hint of a problem in 5 years and it's on the 2nd floor of a 100 year old house with a laundry room right next door vibrating the joists.

Basement is the same setup but directly on the slab.

Ditra isolates minor shifting in your structure from the tile. Bottom line metal mesh has been used for decades and likely will for decades to come but isolating systems like Ditra are gaining popularity as more installers get comfortable with it.

Tim that 9 ply Russian Birch I believe to not be exterior glue and I would be concerned about it delaminating if you put thinset over it.

My thoughts exactly about the Russian birch plywood. Very expensive for the wrong product to use.

Threeapples, you don't live in New Jersey, do you? That sounds like a Jersey mud job, which is not what you want.

No, we live in Ohio. Our tile setter insists this is fine and we have it throughout the house. What kinds of problems can I expect with this preparation?

What about only having one layer of plywood subfloor (3/4" thick) underneath stone tile--is that ok if our joists are very large, engineered wood, and closer together than normal?

I'll answer here rather than over at BAH.... from what I understand the Jersey Mud Job is another term for a thin "scratch" coat over the plywood.

If you have less than an inch of "mud" embedding your wire mesh then you've got a large potential problem.
What I'm hoping you have is over an inch of mud embedding your mesh. If you don't have a thick mud job then you should have used Ditra and not wire mesh.

I'd imagine if you google "wire mesh under tile floors" or something similar you'll see some opinions on the failure of the scratch coat/mesh system.

It's something we ran into when researching how our floor should go down and knew to avoid it. Though thankfully our tiler never suggested it.

Hopefully Bill V will weigh in, or someone with more tile knowledge than me. Good luck apples, you've had more than your share of problems that your GC should have avoided for you. Hope this is just a false alarm.

Hi there, have you seen Bill's "Frequently Asked Questions" ? I know you aren't really asking a general question but I thought if you haven't seen this, it might be helpful. I have linked it below. He has this posted on the gallery side of the bathroom forum, I believe. This link may be from his website, I can't remember. I saved it last year to my desktop when I started my bathroom remodel.

Here is a link that might be useful: Frequently Asked Questions - by billv.

My mistake - it's a 7 ply Baltic birch product and it's specifically designed for tile floors.

http://www.halexcorp.com/halex_underlayment_5.shtml

You need two layers of plywood. You should check the deflection of your joists, to be sure they are suitable for stone. Since they are engineered, you will have to contact the manufacturer for that information.

Thinset is not mud. Thinset is not meant to be applied thicker than 1/4". Is the tilesetter actually using thinset, or mud?

We do not have two layers of plywood. I just read Bill V's faq's--thanks for the link. My husband keeps asking "why do we need two layers of plywood if a grand piano won't crack the floor, what will cause problems with the method of install we have?" For the record, we don't have a piano, I think he is just trying to illustrate his point.

I met with our builder and tile setter today and both think we are ok without two layers of plywood. I cannot force them to redo this area. Our door casings are already installed, the wood floor in areas adjacent to where the tile will go are installed (and they were planned to be flush with the tile), and the baseboards are in. I also called our architect, who exclusively uses our tile setter and he thought these "rules" about a one-inch mud bed or two layers of plywood were ridiculous and he insisted he's never done any of this for his houses and he's never had problems. He said our joists are 14" x 2", engineered wood and closer than typical so we should absolutely not have a problem with our marble and limestone.

I'm still worried about this because the entire internet seems to say that the above-stated requirements are required, but the people on my job don't agree.

I'm not clear on what is down on our floors now. We have the scratch and lath system, according to our builder, and it looks like a metal mesh type material that is screwed into the floor every four inches, and it is embedded in a concrete-like looking material. Thin set will go on top of that at a 1/4" thickness.

I don't know what to do (if there is, in fact, anything I can do at this point).

I think in general, any issues you have during your build, you end up saying, "I don't know what to do (if there is, in fact, anything I can do at this point)"

This is your build and everyone on that site is ultimately working for you. You're the CEO, and if the tile setter, mason, or GC isn't doing their job or doing what you want, then why are they working for you?

If you want it done differently, a headache now is better than a migraine later.

mcclelland, can you explain why two layers of plywood are necessary?

in theory, yes, you're right. ideally i should be able to tell my subs what needs to be done and expect to see only my directives followed, but that doesn't work in every situation. my husband doesn't see this as a big deal so i'm alone in worrying about the tile.

The plywood is to stiffen the floor BETWEEN the joists. That is different than the deflection ALONG the joists. You need to find out from your joist manufacturer what that deflection is. Stone needs a stiffer floor than does ceramic tile.

You are getting great advice on the john bridge forum.

The reason it's different from a piano is that the tiles are held fast to the floor and aren't even slightly flexible or able to swell etc
When the house structure and subfloor shifts, settles, expands etc (and it will no matter whether you have engineered joists set closer than normal or not.... I've got the same set up).....it'll change both along the joists themselves (slightly) and the subfloor itself will also move.
You've already seen this and learned about future changes with your cupping hardwoods.

The tile as its held more firmly than your nailed woods, it can only react by cracking. Either the tile themselves or the grout or thinset or all.

As the experts are telling you it's not been done to industry standards. Look into ditra if you cant have the thicker mudbed.

In other instances you've been reluctant to hold your builder and his subs feet to the fire. This situation is easy. You say YOU chose and hired the tiler....figure out what work he's done and what you owe him and fire him.

We hired the tile setter :/

Yes. So like I said this time you don't need to worry about convincing your builder that his subs need to do things right.
You hired him and you can figure out what you owe him and fire him. It'll be less than tearing up the whole floor a few years down the road.

Unbelievable, with what you have been through I am very surprised you would accept anything either your GC or Architect says without more backup than their word. It seems to me there have been issues with EVERY step of your project so I am really amazed that they are still on the project. Many things have not been done per manufacturers installation instructions and or common and accepted installation practices. And your husbands lackadaisical attitude towards the issues are not helping.

We have had some large projects in the house go very well and exceed our expectations, but, yes we've had lots of hiccups.

My husband completely disagrees that adding a layer of plywood will help strengthen the space between the joists.

It helps strengthen the entire floor system. Whether or not your husband agrees does not mean it is not so. It is a normal practice and the way it is supposed to be done. You may not have an issue but what if?????

"What about only having one layer of plywood subfloor (3/4" thick) underneath stone tile--is that ok if our joists are very large, engineered wood, and closer together than normal?"

For floor deflection, you need to be concerned about deflection in two directions:

Part 1) The deflection of the joists along their length.
Part 2) The deflection of the plywood between the joists.

For the first part, you need to figure out the deflection rating of your floor. Your architect designed it, so he should be able to answer that question. It should even be spec'd on the drawings.

Natural stone tile in general needs a stronger and stiffer floor due to stone not being as strong as a ceramic or porcelain tile. Your stone is thick, so it'll be stronger than a thinner stone tile. But your thicker stone also significantly adds to the dead weight load on the floor.

But your stone is also a soft stone, or a weak stone.

The code minimum for joist deflection is L/360. Again, that's the minimum. A better floor would be L/480. Most engineered joist manufacturers have L/360 and L/480 deflection tables available online or in their printed materials.

In general, for natural stone tile installations you're looking for L/720 as a minimum deflection rating for your joists. You say your joists are "larger than normal and closer together than normal" and that's fine. But that still tells us nothing. Get the info off your joist (it's usually printed on the side) and call the manufacturer. Know the joist series, the joist depth, and the joist on-center spacing.

For your joist series, joist depth, and on-center spacing, they will give you a maximum span the joist can span to achieve L/720. If your span is less than that then you won Part 1).

Part 2) is for deflection of your plywood between the joists, across the 16" on-center spacing, for example. You have 3/4" plywood, which is a good starting point. Hopefully it's T&G. The kicker is that for natural stone installation, you want a second layer of plywood. 3/8" is the minimum, 1/2" is what's usually used. That 1-1/8" to 1-1/4" thickness of plywood provides proper support for natural stone from one joist to another.

The above guidelines were developed to minimize floor deflection. Movement of the floor can cause the bond between the stone and the stone underlayment to break. Or if the bond is stronger than the stone, the stone itself can crack or fracture.

There are isolation membranes that can be used to isolate the stone from movement or deflection of the floor structure. Lathe and thinset is not one of them.

With all that written regarding the need for a second layer of plywood, again, your comment about your "joists being closer together than normal"? Typical spacing is 16" on-center. So if your joists are 12" on-center, that can help dramatically. It may not eliminate the true need for underlayment. But it tilts things in your favor.

Everything written above, it's essentially basic knowledge. No trade secrets. It's not from hidden manuals that are available to the trade only.

Your joists may or may not be properly sized. But your subfloor, especially if the joists are 16" on-center with no underlayment? It's wrong.

If the architect knew that natural stone was going in these areas and designed the house this way, he failed. Then there is your builder. He failed by not knowing or not caring in the first place. Your tiler? He was your last line of defense against poor design and poor construction.

Will you have a problem with your floor? Maybe. Maybe not.

But you certainly have problems with your design and build team if their best response to your concerns is "this is the way I've always done it" instead of showing you actual design numbers to show you that your floor does indeed meet basic trade guidelines.

Good luck.

'My husband completely disagrees that adding a layer of plywood will help strengthen the space between the joists."

He is simply wrong.

Anyone who hasever walked on bulders grade 1/2 inch plywood on 16 inch OC joists can feel the spring from the plywood.

Pianos do not crack if the support under them flexes.
They just need to be tuned again.

A friend was very proud of his baby grand, and could play it at a semi-pro level (and played part time for money).

And then he found out what happened when his wife moved it a couple feet on his living room floor.

Large tile and stone do NOT tolerate the typical 1/360 joist defection allowed for other floor types.

Mosaic (smaller) tiles can tolerate slightly more movement.
Around 6x6 tiles need 1/480 deflection, bigger tiles and stone need 1/720 deflection.

A full inch of plywood on 16 inch OC joists makes sure there is adequate stiffness between the joists.

"My husband completely disagrees that adding a layer of plywood will help strengthen the space between the joists."

And what, exactly, is his expertise in this matter? It doesn't sound like he even cares to research it.

He doesn't have expertise in this field. He suggests that if a kitchen island with thick marble does not ruin the floor beneath it then our marble tile will not cause issues. He says that am extra layer of plywood will not keep the marble from cracking if our house shifts significantly. I can't do anything about this if he and I are not on the same page. :/

In the case of the island you aren't worrying about "ruining" the subfloor beneath the island. The island isn't attached to your floor with thinset and made of an inflexible material. The surface of your marble island top attached to the island with a bead of silicone is a totally different method of adhesion and subsurface than a floor.

Does he think that a marble tile island would be set on a single sheet of plywood? If so then he's wrong there too. Even tile set on an island would have a beefier subsurface than a single layer of plywood.....a double plywood layer or be set in a mud bed. Your solid marble top with a silicone bead spanning the island is totally different than the floor and even different than if you laid marble tiles on the island top.

You're being told by experts (I'm not one) that this is necessary. Do even a tiny bit of research and you can see that it's the accepted procedure and the only method approved by the tiling industry and people who specialize in tile inspections.

It's up to both of you to insist that your hard earned money is being spent correctly. Or in this case built at least as well as a standard spec home.

If you were getting these recommendations regarding industry standards and your wiring/electrician what would you be doing?

It's not your tile that's going to ruin the floor. It's your floor that's going to ruin the tile. Maybe. But that's a maybe that I would not like to risk in my own house. You, of course, can choose to take that risk if you are so inclined. It seems to me that you are not inclined, otherwise you wouldn't have asked and kept on asking about it. You are correct that you cannot do anything about it if you are not on the same page. I wonder why your husband is not on your page. It is his job to support you in what you find important. Clearly you find this important. Have you pointed this out to him? I am sure you would support him in whatever he thinks is important. As stated above, you need to choose your battles. Only you can decide what the trade-offs are worth. I feel for you, I think you are in a very tough situation. Perhaps if you calmly explained to him why the floor the way it is will (most likely) ruin the tile installation ( and that it's not the tile ruining the subfloor), he will see the light. Good luck.

You'll get the "satisfaction" of being able to say "I told you so" when the tile eventually cracks, but that's small satisfaction and a large bill to correct it. The time to correct things is now. I'd also suggest some marriage counseling here as it seems that you are often on different pages as far as priorities, with your concerns being trivialized as not worthy of being addressed properly. You also don't seem to have the ability to stand up and insist that something you want be done regardless of if anyone else thinks you're loopy for wanting it done. Building a home often doesn't bring out the best in people or relationships, and getting a little help to weather this project without a the house or your relationship failing wouldn't go amiss. GW will tell you when your house is at risk (it IS) but a therapist can help you about your conflict resolution issues in your relationship.

You've gotten some excellent, thoughtful, detailed and well documented advice here from some pretty knowledgeable people, along with a pretty solid consensus about both the problem and the solution. I, too, wonder why your husband would be so unconcerned about the potential cost of a failed stone installation down the road; from some of your previous threads, it seems that budget has been a concern for both of you (as it would be for most of us) in which case... I am left totally bewildered by his position. He likes throwing money away? If he were in the flooring/tile business himself, I could imagine he might have a differing opinion (and I would hope never to have him install a floor for ME), but given you have acknowledged he doesn't know anything about this field, I just don't get his reluctance to accept advice. Unless he truly just doesn't care about the outcome. Is that possible? I know, from experience, how tough it is to stand up to contractors who think they are in the right, but stand up you must, and he must stand with you. If he is not willing to back you on something that he knows is important to you (and should be to him!), then the two of you have much bigger problems than how your marble is installed.

If he is not won't yield on this, then tell him that in light of the overwhelming consensus from many with more experience and expertise than the two of you that you are making a potentially serious and costly mistake, you want him to give you a signed affidavit accepting full and sole responsibility for the decision re the installation. Make it crystal clear in that affidavit that you do not agree with the decision. Then if/when the floor cracks and has to be replaced, it's on HIM to get it fixed ... including calling the contractors, arranging for the work, staying home to meet the contractor, overseeing the repairs, and paying for them.

Otherwise, he needs to listen to the advice you have responsibly sought out and so many have offered so generously and competently. If the only opinion he will accept is his own, then I'd suggest you stop questioning things, make HIM call EVERY shot from now on (and accept all the consequences), and focus on things you CAN change. Like sheets ... towels ... husbands? ;)

My husband is a great, supportive guy and I have no plans if replacing him over something like this. He had a lengthy talk with our architect about this and, as a result, said we could put Ditra down because it'd require the least amount of changes (baseboards, door casings, etc), but the architect adamantly disagreed with all the info my husband relayed from this sure and others. My husband respects our architect and believes him when he says we won't have problems. It's very frustrating for me that I'm alone in my fears that we are headed for problems. I am very "by the book" and prefer to go about things utilizing best practice. I can't understand why people on my build aren't this way, but until I get someone on my side nothing is going to change. My husband thinks ripping out the Jersey mud bed will damage the subfloor.

This post was edited by threeapples on Fri, Mar 22, 13 at 19:11

Well, I'll say it one more time. It might damage the subfloor. But that isn't something you need to worry about. It is the GC's responsibility (financial and logisitical) to take care of that. The GC is responsible for fixing AND paying for any and all damage that occurs due to making this right. Are you worried that it will ruin him financially? In all likelihood, the GC's insurance will cover the fix. Point this out to your husband. It's time to stop worrying about someone else, and worry about yourselves and your home.

For Ditra, you'll want to rip out the lathe and mortar that is down now. Add ply underlayment, 3/8" is the minimum. 1/2" thick is better, but 3/8" will work. The underlayment gets screwed to the subfloor, but the screws should not go through the subfloor and into the joists.

Then Ditra over that.

The marriage counseling comments are out of line. Get a hold of yourself.

Follow Mongos suggestions. Don't ditra over the lathe. Find someone who knows how to install ditra and do some reading to be sure they're going to do it right.
I agree that the slams on your husband were out of line. Building a house is a trying time... You'll get through it.

I first found gardenweb years ago when my instincts and minimal research told me that our tiler for our master bath remodel wasn't doing our kerdi shower correctly.

I got advice and support to let me know that the shower as it was being constructed might never last. We sucked it up, paid the guy what we owed him for the amount of work that he'd done up to that point and fired him.

After finding someone who knew what they were doing (they also specialized in tile forensics!) the shower was taken all the way back down to the studs and slab and started from square one.

Yes we lost a bundle of money but we had peace of mind that it was done right and would last. We regretted having hired the first guy but we thanked our lucky stars that GW gave me the knowledge to make it right.

I wonder if you're on the youngish side? One thing about getting to be old geezers is that it gets easier to throw your weight around and make things go your way. This will be your home hopefully for many years and you worked hard for the money you're putting into it... Expect perfection and demand it!

I'm in my mid 30s, my husband is a few years older. We are exploring putting Ditra down. It won't cost a whole lot in comparison to replacing the whole floor. Here are my husband's concerns: will the Ditra interact with the lath we have down, will the Ditra show through the thinset and turn our white marble orange. Do any of you have thoughts on those potential issues?
Thanks

I would absolutly follow Mongo's advise that he posted above on Fri, Mar 22, 13 at 22:31.

Ditra is put under all kinds of stone and ceramic. As I understand it, it is a decoupling membrane that helps prevent shearing (horizontal) movements from cracking the tile.

The subfloor and joist deflection issues help with preventing vertical movement that can also crack the tiles.

How I understand it from the Ditra instructions is that, depending on the subfloor, you select the appropriate thinset to lay the Ditra. Then you lay the tile on the Ditra using appropriate recommended thinset. The orange will be completely covered. It will raise the floor a bit (1/4"?) more because the Ditra has a dimension to it. It is not recommended to be used for tiles smaller than 2" because of the waffle shapes.

I bought the appropriate thinset that Schluter recommended at my HIGH END tile shop. It was expensive but a gem to work with. I have never used low end thinset and don't plan to.

I have linked the site that makes Ditra. Look it over very well. There are great illustrations on how it works either on this site or others.

When I did my floor (first time floor tiler) I used it and, while I took part of it up to get the lumps out, I thought it went well. The beautiful jobs of tiling by Bill V, and Mongct are all on top of Ditra, I believe.

Here is my DH adding extra joists 2x8's to our under qualified 21"oc floor. Now it is 9-10" oc:

Here is after I put down the (specific recommendation from Bill V.) underlayment of plywood onto the subfloor that was existing, and thick and newly re-enforsed. The only mistake I made was I snapped lines for the grid every 4" instead of the 6" that Bill stated. My mistake, but was not a problem for my DS to do:)
{{gwi:1414186}}

Next came my warming floor system, stratigically laid out and planned to the hilt using drawing after altered drawing to get it to all work out. I am proud that I am only 8" short:
{{gwi:1414187}}

Here is the floor with the self leveling compound being poured. It has a plastic lath that I put over the wires. I was recommended by the Moderate End tile store where I was going to buy my warming system. I changed my mind because I wanted 240v. But I had the lathe and I then read a tutorial over on the JB forum about using the lathe, so is used it in my installation. So: the BillV recommended underlayment, warming wire and 2 thermostats (1 is laying there not hooked up, as a backup down the road if needed), plastic lathe stapled closely, primer, self leveling compound:
{{gwi:1414188}}

If you want to do self leveling compound read Staceyneil's thread on the topic from several years ago, I think it is in the bathroom forum.

Here is my Ditra, set with the recommended thinset. After this picture was taken, I did take out some areas, about a foot square, in several places and reset them. I did this because there were large lumps, and I'm a 60yo lady with not as much strength as I used to have. So the thinset was uneven in a few spots. You can see it here. Not all of the lumps needed taking out but several were just too high. When I took it up and reset it it was fine! At this point you can seal the seams with Kerdi tape if you want to water proof it. I was going to do that :( but I forgot!!! If you are installing Ditra in a bathroom, don't forget:)

Here I am setting my tile in the pattern I've chosen. Mongo was taken aback when I posted this because I turned the pattern on him :) He had initially helped me plan this out in a 90 degree angle.

After it had been all laid and grouted with Spectralock epoxy grout:

I post this to help you see the process and that it isn't difficult. The difficulty seems to be when people don't want to make adjustments with installations. There are a lot of people using this stuff.

Edited to add: Please correct me if I am incorrect in anyway. This is how I installed my floor and I may have made an error either in the installation or my description.

Here is a link that might be useful: The Schluter Site.

This post was edited by enduring on Sat, Mar 23, 13 at 12:47

"We are exploring putting Ditra down. It won't cost a whole lot in comparison to replacing the whole floor. Here are my husband's concerns: will the Ditra interact with the lath we have down, will the Ditra show through the thinset and turn our white marble orange. Do any of you have thoughts on those potential issues?''

If you're going to use Ditra, pull up the lathe. The lathe is doing you no good. It's actually a negative. I hope you can understand that for the subfloor that you have and the tile you have going over it, the lathe you have is the wrong thing to use as an intermediary between the two.

After you pull the lathe, then install 3/8" (or 1/2") plywood underlayment, then Ditra, then your tile over the Ditra. Just as I wrote in my earlier post.

The Ditra is only 1/8" thick. It will not turn your marble orange.

Kevin, you haven't read the hundreds of threads on the BAH forum where the exact same thing happens.

Concern expressed about installation problem on shoestring million dollar new build with lackadaisical unconcerned architect and inexperienced and incompetent builder.

Pro's generously give information about correct procedure.

Dithering about re-doing it correctly from OP.

OP unable to do it correctly because husband doesn't think it's important and doesn't really care about what OP thinks and OP won't stand up to husband, GC, or architect herself.

Frustration from all posters who responded.

Repeat ad nauseum.

Green Designs,

You cannot be serious that you know the details of how I interact with my husband, architect, or builder. You also have no idea what goes on in our lives or what kind of people we are.

You obviously haven't read my posts on other GW forums where I described how major projects gone wrong were righted by our builder, subs, or vendors because we stood up to these people and demanded things be perfect.

You all can continue to choose to judge others and draw conclusions about their character, personality, or marriage based on posts made on a home-building forum, but you'd just be perpetuating your childish maleficent behaviour instead of growing up and reminding yourselves that you should have given that up prior to adolescence.

Thanks to everyone who offered helpful advice, links, and imagery--we are now more knowledgeable about what is correct for our floor.

This post was edited by threeapples on Sun, Mar 24, 13 at 21:41

bizarre.

threeapples, you are in a very difficult situation and are correct that the guys on the job often don't seem to know a whole lot, winging it a lot of the time. They don't seem to care about anything, no problem, not worried about it. I am shocked at how loose and unprofessional the construction industry is and the types of things that go on. Ignorance is bliss (pre-internet), lol.

There are tiling standards in place. Check the NTCA for documentation. You should be able to get a manual to support your research and spec the requirements for the job. Maybe you even need to change architects if that's possible?

Building a home and remodeling are said to be one of the most stressful things people go through. Probably even worse post internet! Good luck!

Thanks, snookums. I'm not sure changing architects would do anything now that the house is almost done.

Yes, building can be incredibly stressful and I couldn't agree more that ignorance truly is bliss.

I do hope your architect is planning on being responsible for any poor advice he is giving... And, I hope he has hefty liability insurance. I truly wish you the best 3apples.

"method approved by the tiling industry and people who specialize in tile inspections"

threeapples, this is a good idea. Get a certified tile inspector in there NOW rather than later. Let him prove your team is right and there's nothing to worry about.

There's another organization, Tile Council of North America. I'm not sure if one is recognized more than the other. NTCA is the one that always sticks in my mind for some reason. You will find some other industry links at the bottom of their page:

http://www.tcnatile.com/resources.html

Hot link to NTCA is below.

Here is a link that might be useful: NTCA