Hello:

I am about to apply tile to parts of my OSB sub floor in my 'not-so-super-insulated-house'. My floors were inspected by a tiling expert who said that they were super stiff and that no additional plywood is required.

I was wondering if placing 6 mil poly over the sub floor before applying the cement & tiles would be a problem. The point would be to make changing the tile in the future an easier job due to the fact that the tiles would not be 'glued' to the sub floor?

Any thoughts would be appreciated.

Rob.

I have worked for a good tile installer in my younger days, there are several ways to do this but regardless of method we always began by putting a couple boxes of screws in the subfloor to better secure the plywood/osb to the joists you need a firm base if that floor flexes your tiles will crack, I tore up my fare share of tiles stuck directly to osb without much consideration some were only a few months old, that being said I'm not sure how I feel about your poly idea, maybe it has been done befor I just don't know about it.
beyond that the cheap approach was durock, liquid nailed and screwed to the subfloor thin set and tile.
the right money good quality install, involved, tar paper, expanded sheet metal, stapled to the subfloor on top of which we poured ( for a lack of a better word ) some kind of light weight cement, he called it mud, it was 60 shovels sand to 1 bag of Portland cement barely damp ( can't quite call it a pour ), it's a fairly involved process and you need a good craftsman to do this but it will give you a perfect flat level solid floor, some old houses, even new ones depending how drunk the carpenters were, we ended up with a lot thicker layer at one end to make up, and tiles on top, but that is a permanent install, it's extremely durable hence a bitch to tear out it will outlast the house, I never tore up such a floor but I had to peel tiles off it on a few occasions, once on high dollar new construction we layed a good chunk of floor and the new batch of tiles was a different shade we could not match it, once the owner either cheeped out or the wife was stuck on a certain look that was a cheap quality glazed tile, the glazing had worn fairly quick , another reason I will never considered glazed tile for a floor especially high traffic, those are ok for walls yet they are sold as floor tile too.

The removal was a bit of a bitch but on the new job we actually pulled most tiles up in one piece and reused them, hammer and wide chisel, they popped right up off the thinset, the other same idea we just didn't care to save the tile, there are couple kinds of thinset the wite kind is the normal good enough, there was a gray kind can't remember the name we used on shower walls, same approach there just add as much lie as cement, either way the mud floor did not get damaged

most of all why would you even consider doing this job twice, a good quality install will outlast you and maybe your children, just pic something timeless, marble, granite is kindof hard to work with they are rather fragile until set but there is no glazing to wear off, the next best thing middle of the road and sometimes you can get a steal, on is porcelain tile got them for 50c/sqft before, they have a clear glazing but the look is the actual tile, very durable and 100 years later if the glazing wears off you wont be able to tell it will be called patina by then, my kitchen counter I did that way over 10 years ago no scuffs yet.

the kind of tile that has a red brownish brick color on the underside and a white or any other finish on top those are the glased ones definitely a no- no unless you plan on redoing this just for a workout

George

Rob - how would the tile stay in place if it doesn't adhere to something? Usually a thin underlayment (1/4 to 1/2" plywood is stapled to the sub floor and it would be pulled up and replace if the floor is to be replaced.

yeah I've pulled lots of those glued to stapled lauan? there's a reason for that, those were the kind that most often got cracked, why do you plan on pulling them in the future? I always regarded a tile floor as permanent even if trends change, we always built them to outlast the owner and the next generation, always wondered why would anyone glue them to the subfloor or lauan unless you purposely plan to redo them shortly

Thanks people!

I was only considering the poly as an inexpensive 'uncoupling membrane' sush as Schluter's products: http://www.schluter.com/2080.aspx

I guess that I'll forget it - it was just a thought.

Besides, removing the tile will not be my problem.

woau I did not see that before, not sure how a tile floor would hold up to the years installed on top of those mats layed over the subfloor, there are lots of such innovations coming up every day, I suppose it could work, don't know, I was taught to build a tile floor solid as bedrock, I did pull up lots of lesser jobs because they did not hold up, the whole membrane looks like one of those I'd have to pull up within the first year.

good luck with whatever you end up doing, sounds like you're fixing to flip the house

Thanks George.

No, I am not planning to flip this house - I still have not yet finished building it! It's to be our retirement country house.
The poly idea was just a thought - there will be no poly used.

Rob.

you mentioned removing the tile wont be your problem thought you meant it will be the next owners

there may be something to it considering the other membrane you posted, one would think there is some thought behind it, than again lots of products are on the market that were not well thought out. Who knows.

if you plan on having a solid tile floor, or shower walls for that matter, I'll share what I learned thou that was dam near 2 decades ago, I may be a bit outdated, but they don't build them like they used to, and the craftsman I was working for he was an old timer so some of his ways were even more outdated, whenever we used some box store stuff like durock, it was usually because the money was not right, but that was about the worst we ever done, he would never consider some of the remodel jobs we pulled up and for good reasoning.

I plan on doing my whole house this way, was looking into terracotta but I never done it before so I am not sure how would it hold up, counting the MUD and the tiles should do good for thermal mass.

be sure you pick something like ceramic tile, they can go upwards to $4/sq ft, well used to back then, I'm sure that went up, but we picked up the same quality tile for 50c/sqft at times, depending on the area you plan on, tile stores have such sales when they are down to half pallet of something that is discontinued, we used to clean up such stock weather we needed it or not, it helps to shop early

good luck

Rob - the Schluter products are indeed good products and you would be well advised to install one under your tile if you are not using an underlayment and still a good idea if you are.

Even though your floor is stiff and doesn't need reinforcement, each 4 x 8 sheet wants to move on it's own in response to moisture and temperature, so the chances are good that your floor tile surface will break into 4 x 8 sections as well. Installing Ditra allows the sheets to move under the tile without telegraphing through or cracking. Follow the instructions as to the thin set to be used. In some applications, modified thin set will not dry properly so only unmodified should be used.

Oh, and invest in a good set of knee pads!!

modified thin set will not dry properly

It will dry properly, it's just that busy people aren't willing to wait.

Schluter products are low permeable. Modified thin set is low permeable. Many glazed tile are low permeable. Putting then all together causes problems. Read Schluter's instructions for clarification. Their membranes are not covered by warrantee if modified cements are used.

Right. Like I said, you need to wait extra time for them to dry, but they do and they are fine.