OK, the right thing would be to tile on cement backer baord but… I’m goin to put mosaic tile a 7×6 bathroom floor of 3/4″ plywood with mosaic tiles. These are pre-attached mosaic tiles in a 1 foot sq. sheet. Ordinarily I’d use cement board but I’d prefer to not add the thickness as there is already a step up into the bathroom. And I’d have to take a little off the door so it would open. This is a 1860’s house and I’m assuming the floor was raised at some point to accomodate modern plumbing.
My question is, am i just asking for cracks by tiling directly onto the plywood? Has anyone seen success tiling directly on such a plywood floor? Or should I cement board the floor and tile on that and shave the bottom of the door?
Thanks
Replies
You can install what is called a "slip-sheet". There is an expensive product out there , but my tile installers have used regular vinyl floor sheeting. This is glued down to the sub-floor per spec. and then ground w/ 24 grit discs. A thin film of mortar is then spread over the vinyl and your ready for your mortar base and mosaics. Ive used this method where surface allignment to adjacent finishes are critical.
Good luck!
If the current flooring has a little give or flex to it, then with no additional stiffening of the subfloor it's likely the grout will crack. When compared to watching your lovely tile job crack, pulling and shaving the door would have been the easier thing to do.
Regardless, tile over ply may still crack, even if the subfloor is stiffer than stiff. If the floor is stiff, you could get away with 1/4" cement board instead of half-inch.
Still, check out the current Kitchen and Bath issue that Taunton just published. There's a bathroom remodel the same as described in the previous post...mosaic tile over vinyl.
Gerald,
Plywood is a fine substrate for tile. No slipsheet needed. Just use a good thinset. Or one with a latex admixture.
The important thing is that the floor not flex. 3/4" is probably all right if on 16" centers, but is the lower limit. No unsupported joints in the field of tiles. I.E. no edges unsecured. T@G ply helps. I usually lay 1/4 or 3/8 plywood underlay over any single layer floor.
The standards given on the bags of thinset are b.s. My guess is that the adhesive companies are covering their a$$es by making their requirements so high. 1/360??? Give me a break!
Just my opinion. ( I guess that's obvious, and you get what you pay for on this forum). However, I can say honestly that I've laid hundreds and hundreds of feet of tile over a couple of decades with NO callbacks.
Ironically, The only job I flocked up was in my own house, before I really knew anything about construction, and took advice from a tile store supplier to use particle board as an underlay. Perhaps he was trying to screw me up. At any rate I'm still embarassed about it, altho' only a couple of tiles (4x8) cracked.
I feel like I'm at an AA meeting.....My name is Alan and I was a particle board user. Gawd, I'm glad that's over!!
Alan
Alan, I'm pretty sure L/360 is the maximum joist deflection permitted by code in new construction.Andy Engel, The Former Accidental Moderator
Gerald,
Two houses ago I tiled over 3/4 T&G plywood because I saw Norm Abram on T.O.H. and Dean Johnson on Hometime do it.I had 2x10 floor joists spanning about 9',16"OC.I was lucky to get out of that house in time because trouble with that floor was just around the corner.I could hear it.I agree cement board is way over priced,but for me now it's mandatory.Norm and Dean don't have an ounce of credibility with me just over this issue.
The kitchen floor in the house I'm in now I stripped off four layers of linoleum and vinyl tile,shot a ton of deck screws through the subfloor into the joists,thinsetted cement board and tiled.You can FEEL that it's a great floor when you walk on it.For the size of your project don't scrimp,do it right.And F Norm and Dean.
Barry
Gerald -
I guess the first question that comes to my mind is - why not pull the old floor up down to the joists and start over from scratch? You can gain an extra 3/4" of depth in the flooring system if you rip the existing 3/4" plywood out, screw 1/4 ledgers to the sides of the joists set 3/4" blow the top of the joists, then rip the plywood to fit in this recessed space. Use nothing but screws all the way and plenty of them. Then you'd have room for even a conventional mud set bed or if that's not in your game plan, a good 1/2" layer of cement board, cemented and screwed down to the subfloor.
There have been many, many, *many* new products introduced into the tile and stone veneer marketplace since I was in the trade. But back then it was considered the work of the devil to put tile directly on plywood, especially floors. That's not meant to be an arguement with those here who indicate they do it all the time witn no problems. Just, as one says, my opinion.
Dennis in Bellevue WA
[email protected]
You would never find one tile manufacturer who would say it is okay to lay tile over only a 3/4" floor---I don't think I've ever seen a recommended minimum under 1 1/4". It's up to you, but given that it's your house--I would add at least the 1/4" if not 1/2" durock. I would guess if it's as old of a house as you say it is, and given that they had to raise the joists to accomodate new plumbing--that it would be a stretch to add a mud bed. While this is probably the best substrate for your tile, you better check your framing first or your tile won't be the only thing cracking.
I have had no troubles with tiling over plywood if there is no flex in the floor. First though staple down metal lathe and skim with thinset. The lathe stiffens the floor enough to remove the flex. Also use a high quality thinset/mortar that has a high degree of flex resistance. It's worth the small added expense and time and I've had no grout or tiles crack on me yet. Good luck.
If you use the right thinset (Flex) and the tiles are small enough I don´t see a problem. Test the subfloor for flex: Use a two by four cut to liitle more than room height (use a piece of carsboard/plywood) on the ceiling and wedge. Measure from a fixed line. More than 1/8 inch will be bad under load. How much load? The two by four has to bend slightly. Not scientific...but works. se between centers of beams.
Just a thought from Germany, Mathias http://www.raulfcarpenters.com
P.S.: Use the best grouting compound money can buy.
Edited 11/6/2003 2:58:53 AM ET by Matt
Backerboard does not reduce joist deflection. If the floor moves/bounces the only way to correct it is to strengthen the joist.
The reason you don't want to apply thinset directly to plywood is that the plywood will suck the water out of the thinset before it can setup and harden, turning it into powder. You could use a mastic but you can't have any failures/voids in your grout because the mastic will soften up when exposed to water.
Yes, you are asking for trouble. Elevation gain is the number one reason why folks don't follow Tile Council guidelines and try to cheat. Plywood is, of course, wood. It expands and contracts in wildly fluctating measures. Masonry products dont expand and contract so much. So fitting the two together without out a membrane is asking for trouble. Your tile will crack. Get a tiling book by either John Bridge or Michael Byrne. Both are great texts. Here are your options:
The traditional method is a mud bed, but it will add an inch and a quarter to your floor.
The "modern" method is to apply thinset to the plywood and lay down some backerboard. They come in half and quarter inch thicknesses and will add that number to your floor.
There are some new products out there which only adds an eighth. Called "Ditra" it is made by Schulter Company. Pronounced Sshlooooter. Thinset it down and tile right on top. Nice stuff. Exepect to pay an additional buck a foot for it.
Me, I do this for a living. Depending on how old your home is, I'd probably go first with a mud bed, then to Ditra, then to CBU. I'm a mud bed kinda guy. To me, the tile installation determines the elevation, not the other way around. In other words, I tile it right, and whatever the elevation is, is what it is. I don't let elevation determine how I do things.
You can cheat and actually lower elevation in a room by ripping out the plywood and installing ledger strips along the side of each joist and then nailing plywood into those. The final elevation is the height of the joist. Then add a quick quarter inch membrane and tile away. I don't like this method but have used it in emergencies. I actually like it to decrease elevation for a mud bed.
Let me add this. Mosiacs are very small and translate every bump and hump and ridge in the setting bed. If the plywood is not dead flat or there are lips or ridges at the edges, the mosiac will lift up and look like c r a p. Unlike larger format tiles, you can not compensate by switching to a larger knotch size and increasing the thickness of the thinset, because the mosiac is only 3/16ths thick. If you try that, the thinset will ooze out and become a mess. So your setting bed (plywood, Ditra, CBU, mud bed) has to be dead flat. Put a straight edge over it and see what you are dealing with. You may be stuck with installing CBU or a mud bed.
Good Luck!
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Thank you all so much for your responses. I just ripped up the rug and found it to be glued to 9" square tile like material which was glued to the plywood. I don't know what it is. It's fairly brittle and cream in color. I could post a picture if anyone would like to see it. Anyway, there is delamination of plywood subfloor near the tub and near the toilet. So I'll probably replace the whole subfloor and go from there.
Thanks again all.
The plywood delamination should be a wake-up call, Gerald. Like Boris, the first and highest level of quality installation procedures calls for a mud set job. Since the plywood is gone, take our advice and rip it all up, install those ledgers and float a "real" setting bed for your tile. If this is beyond your skill level, I'd consider finding a good mud mechanic and hire it done. I've been around construction all my life and have been known to try at least a little bit of almost every trade. But there are some things of major scope I won't attempt.
...........
Dennis in Bellevue WA
[email protected]