I have put down durock over old tong and groove subfloor planks. I first added screws through the subfloor to the joists. I then laid thin set down and put the durock over the thin set and again screwed through the durrock into the joist with 2 and 1/4 inch screws. I am left with a floor that has a gentle slope and one little hump hard to really see but I know when I tile I will see the hump, they are 12X12 tiles and I will see the drop when looking at the tile with tub giving perspective. I am planning on pouring self leveling cement (with primer) over the durock to get a more perfect and level floor to tile on. It is a 8 foot by 5 foot bathroom. I probably won't cover the entire floor just the most extreme spots which really only amount to a half an inch across the entire floor. I wanted to know if this sounds like a good plan to get a more level floor for the tiles. Please let me know your thoughts!

thank you

I sure hope you didn't spend the money and pour the self leveler yet.

All your durock needs to come up and the thinset scraped away

Durock (or any other cement board) CANNOT be installed over dimensional lumber subfloors. You must install a layer of 1/2" bc graded exterior (exposure 1) plywood over the plank subfloor, fastened with coated deck screws to the plank subfloor every 8" within the field and every 6" around the perimeter. Do not screw the underlayment plywood into the joists. Do not use any adhesive between the plank and plywood. Long edge of the plywood crosses the joists, even if it's more convenient to run it the other way. Maintain a 1/8" gap between sheets and a 1/4" perimeter gap.

When you go to reinstall your cement board, secure it only to the floor, do not screw it into the joists either. Maintain the same gapping as you did with the plywood. Any leveling gets done over the cement board and I read that you are aware of the primer.

I decide to go back and check out your other posts, see if any were related to this project and see if maybe you got the durock info off this site. Sorry, I'm not a plumber so I don't look over there in that subforum often, just a quick glance for key word like "shower" or "tub surround." Had you posted in the interior home improvement section, you would have received the correct advice from the beginning of the project. I can say with certainty, though, that Milo by no means intentionally steered you wrong, and he can only go by what he sees other tile installer do on jobs where he is working. Unfortunately, he's worked around a lot of really bad installers.

When you do go and add the plywood, make sure you use plywood that is bc or better. The letters used to describe the plywood, A thru D , the higher the letter, the larger the defects are allowed. the frist letter always describes the plywood face layer and the next letter describes the veneers below. "A" is very clear, would be used for making cabinet boxes. "B" is the next step down, knotholes are cut out and plugged with clear wood, etc, etc. by the time you get to c and d, you have some pretty significant allowable defects and anything rated "CD" or "sheathing" is unacceptable under ceramic or stone as the plywood can have huge sections of nothing between the face and bottom veneers as the poor graded veneers are stacked together. The lowest allowable plywood is "CC plugged" which is wjere the knot holes over a certain size are cut out and replaced with a plug, but BC plywood is so much easier to find. I bring this up because in a previous thread, you mentioned that you bought cdx for the floor. I saw you were told not to bother with it, but I don't know if you still have it, if you intended to use it given the beginning of this response.

Good luck.

I recently did the same type of remodel. The self leveling concrete is excellent. Just keep an eye on it after pouring - it will continue to move as it dries. Bear in mind the weight you are placing down as well. After it is pretty close to level, skim coat it with feathering concrete. You can also make up minor un-levelness when you install the tile.

The floor seems rock solid. There is no deflection whatso ever due to the planks. I don't see the need to pull up the durock as that would probably destabilize the floor and the ply would raise the floor too high. It is a shame because I was planning on addressing this way back. I have not poured the self leverer yet. I sense that you want the floor disconnected from the joist in case they move. The load bearing cement wall is directly under the bathroom providing much stability. The hump is definitely caused by settling over the load bearing wall but seems to be very old and stable currently. Either way we are really talking about 2 and a half tiles wide visible along the floor. Does everyone agree with the need to pull up the durock?

Hi Jjustinia:

Bljack is absolutely correct and really knows his stuff. The fact is that durock (any cement board) should not be installed over tongue and groove flooring as this type of flooring can buckle over time and start to crack/pop the tile/grout floor.

That being said, I have seen many contractors get away with installing it just like you did with no issues that I saw as many as 10 years later. I have also seen where the tiles and grout cracked and the job had to be redone less than a year later.

I never liked doing it, but always removed any tongue and groove wood and replaced with plywood... yucky, hard work but being a contractor that doesn't want to have to go back after a job we simply had to do it according to manufacturer recommendation... can never go wrong with that.

In my opinion, if you lift and fix now you can be absolutely sure that you won't have issues down the road. If not, well, when the tiles crack/pop you certainly can't blame Bljack... ;)

Hope that helped a little!

MARK

Quote:

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Originally Posted by jjustinia

the floor seems rock solid. there is no deflection whatso ever due to the planks.

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I never once commented on the deflection of the floor. 3/4 tg planking is strong. It's dimensional lumber, though, and therefor, too unstable. Every year it changes with the seasons, cupping/bowing, gapping opening and closing. That is the movement you need to isolate. That is why you needed a layer of plywood. Securing the durock to the joists made a very bad situation even worse.

Quote:

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Originally Posted by jjustinia

it is a shame because i was planning on addressing this way back.

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I know you did. It's too bad no one there though to have a moderator move it to a more appropriate forum. Kind of was like going to a cardiologist for contact lenses. Wouldn't have mattered much if you did though, you had the wrong kind of plywood, the cheapest kind, not good for anything but nailing siding into it. IF you had used it, you would have risked deflection issued just from the possibilities of large hidden voids within the layers of the veneers AND since it's square edge plywood, you'd have needed a second layer over top anyway. Single layer subfloor systems must be t-g plywood or osb or have solid blocking between the joists where the panels cross the joist bays.

Quote:

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Originally Posted by jjustinia

i dont see the need to pull up the durock as that would probably destabilize the floor and the ply would raise the floor too high. does everyone agree with the need to pull up the durock?

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Additional plywood will never destablize a floor, only strengthen it. 3/8" plywood and Ditra will be the same height as the floor is now, 1/2" plywood and Noble CIS will be about the same as well. Either membrane will outperform any cement board any time as well. It's too bad you got such incorrect advice, however, you are not that far into the project. I am a bit confused by your question at the end of your reply... did you come to this forum to kearn how to do it correctly or to get some anonymous person who you will never meet tell you it's OK to do a hack job in your bathroom? There's no tile police, if you want a hack job, do one. 30 people posting leave it like you are doing it will just mean 30 really stupid people replied. How many people will need to say leave it like it is before you feel fine about screwing it up??

The only person you should be asking is the person who answers the phone when you call USG's technical support and explain to them exactly how you prepared the floor.

USG 1 (800) 847 4968

So I got really horrible advice from Milo Dolezal. I am not sure of your qualifications bljack, and you were the first to respond. How am I suposedto know you are not one of the stupid people you are referring to? I wanted to see if there was a consensus. I listened to one person before and it was the wrong advice. Why would it be wrong to get a second opinion, to continue your medical metaphor. We are talking about less then 3 sheet of the small size of durock- 4 feet by 32 inchs. Most of which will be coverd by a 60 inch double vanity. I was worried about the process of breaking up the thin set tearing up the existing subfloor. If I put 1/2 inch ply on the sub floor and then durock or some other backer I would be over a half inch higher then I am now. So I don't understand your suggestion that it would be the same height. Unless you are suggesting first cutting out the tong and grooved planks, which is what I wanted to do in the first place. I am very fustrated.

Trust me when I say I completely understand your frustration. I know how much work goes into just the steps you've done so far, so to back track is very annoying. Milo certainly didn't mean to give you incorrect advice, and it is unfortunate that it happened. You will be much more frustrated, though, when later on you are constantly fixing cracked grout lines or loose tiles or worse, pulling up the whole floor and starting over.

In keeping with the medical metaphors, no, this time will be a simile (I think, 7th grade English class was 29 years ago) whereas the FDA regulates pharmaceuticals but not herbal supplements, trades such as plumbing and electrical are to pharmaceuticals as flooring and painting and trim carpentry are to herbal supplements. I can only bring to you my own knowledge of 20+ years of tile installation and countless time at training seminars at various tile distributors when different vendors would bring new products to the market.

The plywood methods I mentioned would completely eliminate the use of Durock. Ditra is a tile membrane that is 1/8" thick, installed, so coupled with 3/8" plywood, it would be the same thickness as the current floor with the durock. Noble CIS is 1/16" thick installed, and when coupled with 1/2" plywood, it would be at about the same height at which you are now. When a membrane is used, you skip the cement board.

Good Luck.

PS I set my first tile when I was 8 years old, along side my father. That handsome looking guy struggling to reach across the counter to the bcksplash is my 11 year old, he was 9 at the time. Proud Papa. :)

Well I took your advice and called usg the only expert I should trust. They said while they don't have a specific recommendation for use over planked sub floor and would recommend ply or osb, they did not feel it would be a problem on such a small area or even a larger one. Their concern was deflection, as durock is not structural, and not expansion and contraction. Their concern was that the planks be perpendicular to the joist and not in line for support. I told them mine was at a 45 and they said that would be fine. They would not have told me to do it the way I did it but did not feel it should be ripped up. They said from the way I described it that it was solid and that was their concern. The thin-set compensated for bulging and inconsistencies in the planks and the fact that a load bearing concrete wall was supporting the joists directly und the durock created a solid base for the tiles. Again we are talking about less than 20 spare feet the expansion and contraction across that small of an area would be minimal if there was any at all as the wood is aged and stable. There is no doubt that I should have spoken with you prior to listening to milo. I was given bad advice. But the question is whether I need to rip it out. I have a hernia and need surgery and need this wrapped up for my family. I can't physically handle the stresses of hammering out the thin set and I am running out of time and can't afford to hire some one. From usg point of view its not a problem.

First and foremost, good luck on your surgery. As for your floor, it was never a deflection issue, it was an issue of the stability of dimensional lumber under the tile. I've ripped out installs in pristine for cosmetic changes and as I ripped them out, I wondered how they ever lasted even a week, and I've seen installs that should have survived anything short of a nuclear blast that fell apart. I hope for your sake that you are the exception to the rule.

I know that it was not a deflection issue from your point of view, but it was from USG's point of view. You point of dimensional lumber stability was not a concern for them, especially considering the squre footage involved. Also I don't know if this makes a diference to you but I am not tiling the bottom of a shower I am just tiling the floor to be used exclusively for walking in front of the vanity and a bath tub. I have received your point loud and clear and wish that I had this quality advice prior to milo's poor advice. I would have done as you suggested, again it is what my spidy senses told to do and I was talked out of it. Thank you for the medical well wish. I would tear it out if it seemed unstable. But it is a rock and seems like it won't be a problem. I am going to use silicone calk in the grout spaces under the vanity to separate the tiles under the vanity from the visible area to lessen the stresses and give expansion and compression areas. USG liked this plan. We will have a total of two grout line visible anlong this length- surrounded by silicon calk for movement.

Hmmm, you see what happens when you are supposed to be doing a job outside and it's just raining and raining? Besides making no money today, and getting drenched when a gutter seam came apart sending water into the basement, I get to frequent these boards and ponder. I ponder with the same obsession that would have me critiquing the tile installation in a strip club without even noticing any women present. So what did I ponder?

There is a floating ceramic tile floor system on the market that actually works, call Snapstone. No, I'm not suggesting that, however, the grout that is used for that system is a urethane grout called Starquartz Grout. It's used with that floor system because it does need to maintain some flexibility but it's not a garbage bucket of colored acrylic caulks like the big box stores market as premixed grouts. Maybe something like that would provide some flexurial (sp) capacity over the entire installation?? It's not cheap, but something to consider.

Thanks for the toughts, I really was only thinking of the grout under the vanity where no one will see it. In fact, is there even a need to grout under there. I am just trying to detach as much tile as possible so the two rows that are visible and grouted together might just float together with less stresses on them.. also should I not complicate the issue with self leveling cement and just do the best I can with ultraflex 2 mapie (sp?) thin set.

Any General advice on how to go about layout the floor tiles. They are 12 X 12. The room is not 100% square, but its not that bad. So I am trying to figure out how best to account for this so that it is less noticeable along straight edges like in front of the tub or along the front entrance saddle, in front of the vanity. I was thinking that having the full straight tile in front of the saddle and tub were the most important and have all the rest of the tiles slip under the vanity and cut on the far end of the room as needed. This way you see full tiles when you first enter. I can see that the far end would have 40% of a tile. Your advice would be helpful.

this is my bathroom lay out.