Any advice on suitable underlayment for tile would be appreciated. Sublfoor is 3/4″ thick Advantek over 12″ I-Joists 16″ on center. Is 1/2″ sheathing ok for kitchen and mudroom? Bathrooms?
Thanks
RMB
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Replies
If you are going to tile directly on the plywood it needs to be better than sheathing grade.
http://forums.taunton.com/tp-breaktime/messages?msg=114690.1
Recent thread on this subject.
William the Geezer, the sequel to Billy the Kid - Shoe
You'd probably be fine with it... I know a few that are working fine in that configuation, but...
Total sub + underlay should be min 1 1/8"according to most tile manufactureres. If you are installing on the ply, get bcx grade and tile to the "b" side.
I like 5/8" bcx as an underlayment, 1/2" Hardiebacker applied over bond coat of thinset with screws on 6" centers, then 1/4" tile....
it matches up perfectly with 3/4 finish in place hardwood.
A La Carte Government funding... the real democracy.
5/8" underlyament + 1/2" Hardibacker + 1/4" tile brings me to 1 3/8". How dow this match up with 3/4" hardwood? Am I missing something?
RMB
"5/8" underlyament + 1/2" Hardibacker + 1/4" tile brings me to 1 3/8". How dow this match up with 3/4" hardwood? Am I missing something?"It doesn't match up. You'd need a transition strip.That's where Ditra and Dita-XL come in. Over Advantech you use, depending on the thickness of your tile, either Ditra or Ditra-XL. Then tile over that. The "thinset/Ditra/thinset/tile" thickness can equal the thickness of your hardwood floor, thus the top of the tile and the top of your hardwood will be at equal elevations.Edited 1/10/2009 3:57 pm ET by Mongo
Edited 1/10/2009 3:58 pm ET by Mongo
5/8" Underlay Everywhere (Tile, Hardwood, Carpet)A La Carte Government funding... the real democracy.
i'd like 1/2" Advantech over the 3/4
....Advantech makes a nice tile base
Mike, I haven't been to the site in awhile. The Hussein is new- glad to see you flaunting your Arab roots. But you stand alone on using Advantech for underlayment for tile- no one else seems to agree. And yet Advantech boasts of it's water resistance, which we thoroughly tested this summer when it rained nearly every afternoon until we were dried in.
RMB
Go to the manufacturer's (Huber) website or call their tech department and see if they recommend Advantech as a tile backer. Of course I can save you the trouble and tell you that they don't. Advantech is not a tile backer. Do some people still use it as one? Sure. But Huber tells you not to affix tile directly to it, instead they tell you to use a transition material...cement board, Ditra, etc.
i like the advantech... and my tile man likes the advantechi like it with that paint on membrane... the one that dries red ... so.. 3/4 advantech, + 1/2 advantec = 1 1/4........ and the paintable membrane.... good to goand i say that with fear and trembling in my heart, because mongo said no gohttp://forums.taunton.com/tp-breaktime/messages?msg=67972.1672"Redguard"Mike Hussein Smith Rhode Island : Design / Build / Repair / Restore
Edited 1/10/2009 8:36 pm ET by MikeSmith
The subflloor does need to be at least 1 1/8" as others have mentioned. However, no one has mentioned the deflection of the I-joists, which depends on their span in addition to the information you provided. It sounds like the spans will be different in the different rooms you mention.
I don't have a deflection calculation for I-joists, but here is one for regular wood joists:
http://www.johnbridge.com/vbulletin/deflecto.pl
It sounds like the 12" I-joists 16" OC is likely a conservative design (this is a guess without knowing the span), but if you have concerns there may be excessive deflection that could ruin your tile job, you can add a layer of Ditra over the 1 1/8" minimum subfloor to help decouple the subfloor from the tile. Or go ask at http://www.johnbridge.com
Natural stone can handle only half the deflection (L/720) as ceramic tile (L/360).
Billy
Edited 1/10/2009 10:35 am ET by Billy
The span is about 15' and you are right, this house is very strongly built. There is no perceptible floor deflection. If cement board does not offer any structural benefit, what does it do? Sure it is water proof, but I don't plan on submerging my kitchen floor.
RMB
Cement board is a transition material. It takes you from the plywood to the tile. Tile sticks to cement board. Cement board can be attached to plywood.Therefore it allows you to tile over plywood. Sort of like equivalent equations.
Man, this is several posts in one day, even worse, several posts over the period of a few minutes. I think I've exceeded my allotment. I need to go watch some football.
A couple of small items; some apply to this thread, others don't but I'm gonna toss them out anyway...
Do not tile directly to advantech. It's not an approved installation method.
When we talk about the "recommended base" being 1-1/8" to 1-1/4" thick, that's the combined thickness of the subfloor or subfloor and underlayment. Cement board is not structural and it's thickness is not to be considered part of that 1-1/8" to 1-1/4" thickness.
If using a cement backer board, the cement backer should be thinsetted and screwed to plywood. Cement board should not be installed directly over a wood plank subfloor. The thinset is not to bond the cement board to the subfloor. The screws do that. The thinset fills any micro-voids between the cement board and the plywood so that there is no movement between the two when the floor is walked upon.
If tiling directly to plywood, don't use a CDX grade ply. Don't use modified bagged thinset. Buy bagged unmodified (dryset) and modify it yourself with liquid admix. That gives you a better product than bagged modified.
Natural stone needs a stiffer subfloor base than ceramic.
Large format tile might (not always) need a thicker setting bed (1/2" square notched trowel versus 1/4") of thinset than regular format.
So RMB, your original question:
"Any advice on suitable underlayment for tile would be appreciated. Sublfoor is 3/4" thick Advantek over 12" I-Joists 16" on center. Is 1/2" sheathing ok for kitchen and mudroom? Bathrooms?"
Mudroms and bathrooms can suffer from standing water, so I'd actually recommend using a membrane like Ditra. When you Kerdi the seams you end up with a watertight installation.
If you do go with Ditra, your 16" joist spacing and the 3/4" advantech allow you to apply the Ditra directly to the advantech. You don't need that extra 1/2" of ply underlayment. There are two versions of Ditra; Ditra and Ditra-XL, with the XL being thicker. Depending on your tile thickness, you'd choose one or the other if you want the top of your tile to be level with the top of an adjacent strip hardwood floor.
If you don't want to go with Ditra or any other type of uncoupling membrane, then you'd need the previously mentioned 1-1/8" to 1-1/4" plywood combo. Then you could either tile directly to that (which I don't recommend for a DIY mudroom or bath), or then on top of that 1-1/8" to 1-1/4" thickness, you can thinset and screw a layer of cement backer board and tile on the cement backer board.
Toodles,
Mongo
Hi Mongo- you get the prize for the most thorough answer, although I must confess to being even more confused after reading all the posts and browsing all the DYI (Do Yourself In) books in the home section of Barnes and Noble. Underlayment seems to be an area where different opinions proliferate as fast as failing mortgages!
According to your response if I opted for cement board I would still need to add at least 3/8" (but lets assume 1/2") of plywood first. So what good is the cement board?
CDX grade was recommended because it's coarse surface offered a better bond for the tile bed. I am skeptical because I would worry about all the inevitable voids in CDX.
Now I have to admit "uncoupling membranes" are new to me. Is this to prevent the tile from cracking if the floor moves? Isn't there a downside to sacrificing a bond between the tile and the floor? Did uncoupling membranes even exist ten years ago? How many floors were laid without them with no problems?
Why is there a concern about DIY tiling directly to plywood? How does this differ from tiling to the cement backer board?
Never heard of Ditra but I will check out their website. Is it similar to the Schluter systems?
Sorry for all the questions, but you appear to be a pro and I would appreciate your comments.
Thanks, RMB
Cement board is not waterproof, but it doesn't degrade when wet.
Properly seamed Ditra or another underlayment can give you waterproofing.
Uncoupling membranes are fairly new in the U.S. but they have been used in Europe for much longer. Ditra is dimpled with squares that are cut in a dovetail shape so that it maintains a good grip on the thinset above, even if there is some movement between the tile and the substarte under the Ditra.
Lots of people tile directly to plywood but it is not recommended. It's better to install cement board or Ditra according to Mongo's instructions and tile to it. Plywood has a different coefficient of expansion than tile and it will move seasonally, so you are putting stress on the connection between the tile and the substrate. And if the plywood gets wet...
Billy
<Now I have to admit "uncoupling membranes" are new to me. Is this to prevent the tile from cracking if the floor moves? Isn't there a downside to sacrificing a bond between the tile and the floor? Did uncoupling membranes even exist ten years ago? How many floors were laid without them with no problems?>
You got it- they allow the layers to move. The Romans used to use layers of sand as uncoupling membranes. Some of those tile floors lasted for centuries.
k
Some other have answered some of these, but I'll chime in to keep things concise and organized:
"According to your response if I opted for cement board I would still need to add at least 3/8" (but lets assume 1/2") of plywood first. So what good is the cement board?"
As other have mentioned, cement board is a transition material between wood and tile. Wood moves at a rate different than tile. Variations in movement are what can cause the bond to break. So you screw and thinset the cement board to the plywood subfloor. The screws hold it tight, the thinset prevents up/down flexing. You then tile on the cement board. Since cement board and tile are compatible, the bond is unlikely to fail.
"CDX grade was recommended because it's coarse surface offered a better bond for the tile bed. I am skeptical because I would worry about all the inevitable voids in CDX."
If you're set on tiling directly to the plywood, you want a better grad of ply for your underlayment to give a better base for the tile, and you want a really good thinset to get the tile to bond to plywood due to the differing rates of movement between the two. I'd recommend Mapei's Kerabond and Keralastic.
"Now I have to admit "uncoupling membranes" are new to me. Is this to prevent the tile from cracking if the floor moves? Isn't there a downside to sacrificing a bond between the tile and the floor? Did uncoupling membranes even exist ten years ago? How many floors were laid without them with no problems?"
Yes, uncoupling membranes uncouple the tile from the floor. To a certain extent. Uncoupling membranes have been around forever in one form or another, they're quite common in commercial. Remember, in residential we used to have tile over full mud jobs...a couple inches of portland-cement mud reinforced with diamond lathe. That's a solid backer for tile. Over the past few decades we've been moving towards lightweight construction in residential...no more mud beds. With lightweight wood frame construction, you get movement. With movement, you get cracked tile. So that's why you're seeing uncoupling membranes making their way into residential construction. To simplify, they isolate the tile from the house movement. The house moves. The membrane takes up the flex. The stress put on the rigid tile and grout is minimized.
"Why is there a concern about DIY tiling directly to plywood? How does this differ from tiling to the cement backer board?"
Because they mess up the installation and the seams between the sheets of plywood end up telegraphing through and cracking the grout, and tiles end up popping off the floor. It's a more challenging installation. Can it be done? Sure. But do people mess it up? Sure. It's just best to be forewarned, that's all.
"Never heard of Ditra but I will check out their website. Is it similar to the Schluter systems?"
Ditra is made by Schluter, the same company that makes Kerdi. Someone a few posts back wrote "save your money, don't use Kerdi" and they are correct. Don't use Kerdi. Kerdi is a waterproofing membrane used in showers and tub surrounds. Here you want an uncoupling membrane, and that's what Ditra is. Ditra itself is also waterproof, but for the entire installation to be waterproof you need to treat the seams between adjacent pieces if Ditra, and that's done using strips of Kerdi.
Conclusion?
Over your Advantech you can either:
1) install 1/2" ply, then cement board, then tile.
or
2) install Ditra (or another uncoupling membrane) then tile.
Now you can do it other ways and have a successful installation, or you can do it other ways and end up with a failed installation. Heck, you can do it one of the above two ways and still have a failed installation.
But the two above are considered acceptable methods by the material manufacturer's and by TCNA, and should maximize your chances for success.
Oh, and if you do install underlayment over your subfloor, do NOT screw it into the joists. Just screw it into the Advantech. If you don't use cement board and tile directly over the plywood, again, use the Kerabond/Keralastic.
Don't watch HGTV for inspiration either. ; /
Best, Mongo
all U forgot was to add "drink belgian beer" ...
Thinking I'll copy your advice and read it to myself!
great answer(s) ...
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
What mongo wrote - that is really some super solid advice.
I think an uncoupling membrane is cheap insurance on any DIY floor tile job... what's the cost of failure vs. the added cost of Ditra?
It's also a bazillion times easier to put down than cement board (for a weekend warrior... cutting/snapping/scoring/screwing heavy cement board vs... unrolling the nice, lightweight ditra and cutting with a utility knife). Need to cut a hole in cementboard? average DIYer... that's a chore. in Ditra? snip-snip, done.
And, it gives you better water protection... and people usually end up tiling in places that have water... bathrooms, laundry rooms, kitchens, entry rooms....
Big fan of ditra. There was a FHB cover story on the stuff a little while back... if you have online access to the articles, do a search.
Edited 1/11/2009 9:33 am ET by GraniteStater
Thanks for a clear and thoughtful response. Ditra it is, although I will probably use 1/2" plywood underneath to bring the tile level with adjacent hardwood.
RMB
Look at the Ditra-XL. It's intended for exactly that purpose and it might save you the trouble of having to install the 1/2" ply underlayment.Also follow Schluter's advice regarding what type of thinset (modified vs unmodified) to use below and above the Ditra.Glad to have helped.
I've really been following this thread with interest, as I'm a DIY'er and I'm about to tear out the 50 year old mini tile on the floor of two bathrooms and retile with something that SWMBO likes better.The comments about a full mud bed reinforced with diamond weave strikes a chord as our old floor has a full mud bed with diamond weave reinforcement. Is it a waste of time to try to save that mud bed or should I just demo it to the joists and start over, following the advice given in this thread so far for underlayment?Mike D
Edited 1/11/2009 7:01 pm ET by Mike_D
Geez
A lot of complicated and expensive solutions.
I wont tell you what to do, but I would not attempt to use a Kerdi or water proofing membrane on it unless I am putting in a floor drain, sloping it and making a wet room. (Never had a problem with a tile floor yet and never waterproofed)
The 3/4" avantech is quite strong. I'd likely use 1/4" or 1/2" hardi thinsetted and screwed to the deck (into the joists) and set my tile.
Yes the tile institute might say it is not the ideal recommended but we have done lots and lots and lots of homes and never had a problem. We did have some problems back in the old days when we pushed the spans and used 1/2" plywood over 5/8" t&g osb sheathing. (tile floor blew apart, cracked, etc)
Thats my 2 cents worth.
Keep it simple