I am about to finish our master bath (finally). It is an old house but this is new construction. Right now there are studs and the floor consists of 3″x8″ joists 16″ on center and they span about 13′. The house is very solid. The rough flooring is 1×8. I have patched (screwed) in some new boards where the old were cracked or split.
What is the best way to prep for a tile floor?
Should I just screw down the the existing boards and lay some plywood over them and then some concrete board? Should I remove the existing 1×8’s and replace them with 3/4″ plywood and then more plywood and concrete board? Something else?
Height is not really an issue as there is only one transition into the bedroom and I can make it work regardless of which floor is higher or if they end up on the same plane.
I looked on the John Bridges forum and I had some trouble finding what I needed. It seems very specialized.
Is putting some 1/2″ plywood & 1/4″ concrete board over the 1X8 enough? The room is only about 8′ x 9′ so either way is not going to break the bank. I would prefer to do it once and never have to worry about it again.
Thanks for the help
Replies
I'm not a high end tile setter, but what I usually do is put 1/2 or 3/4 ply down. Screw it to the joists as well as in between to the sub floor. Then I put down either 1/4 or 1/2 cement board, thinset underneath and rock screwed down.
The 3/4 really solidifies the floor, if I have the space. The cement board, I feel, gives better adhesion for the thinset when setting tile.
As a standalone subfloor, meaning not considering the existing 1 x 8 subfloor already in existance, I think most people would reccomend 3/4" as the minimum subfloor thickness. On that basis alone, regardless of whether or not you end up keeping the 1 x 8, I would plan on going with 3/4", because as you say height is not an issue
I'm not a tile pro, however, so wait to hear from more of them.
"Oh, this is the worst-looking hat I ever saw. What, when you buy a hat like this I bet you get a free bowl of soup, huh? Oh, it looks good on you though."
If the existing floor is flat and level, or at least to your satisfaction; I would glue and screw 3/4 exterior ply over it and tile away. I've only done this perhaps several hundred times, so don't just take my word for it.
If it aint flat or level I would do a mud job, over tarpaper and galvanized wire lathe.
You're gonna get about 6000 more and different answers. Three more layers of plywood, two layers of cement board fastened with stainless steel screw 2' OC and a step ladder to get in the room!
Good luck.
Eric
[email protected]
It's Never Too Late To Become What You Might Have Been
I know what you mean. The "kids" bathroom was done with concrete backer board in the tub area, greenrock in the rest of the room and 3/4" cdx plywood screwed to the 1x8 floor. I thinsetted the tiles to the floor and afterwards I got like 12 different opinions as to whether or not I should have used concrete backer board on the floor. The tile place said not to, so I didn't, but many contractors swore that the floor would crack. It has been 12 years and the floor is still fine.
I guess the fact that I screwed the heck out of the 1x8 and 3/4" ply made for a stable enough base to support the tiles. I did not have any problem with the tiles adhering to the plywood so I don't know if the concrete backer would have made a difference or not.
Since I do like 1 tile job every couple of years I figured I would ask those with more "current" knowledge. Is concrete backer board advisable on the floor or not? Also, should it be used everywhere the walls are tiled? Since it is my own house I don't mind the additional cost or labor if it makes the job better.
Durock, CBU, or "concrete board" offers no structural stregnth to the floor system. That is why if you do use it, you still need two layers of wood, subfloor, underlayment and then, CBU on top of all of that.
While plywood may not last more than five to ten years under EXTREME wet conditions, I don't see how adding CBU on top will lengthen it's life. When I say extreme conditions, I'm talking about 5 kids having a party in the tub and leaving the water on the floor to soak in. Do this every night, and I'm sure you can see the potential for problems with the underlayment, and any area below as well.
I am finishing now, a kitchen and foyer floor for another contractor. I put 1/2"cdx over the 1/2" subfloor, then CBU on top of that. I was ready to just put 3/4" and be done with it, but fo some reason the ho and the GC seem to think this is "better". Whatever.
There are waterproofing membranes that you can install (google Schluter.com) or brush on, but you still have those pesky joints at the front of the tub or shower, and at the walls.
3/4 ply ontop of your 1x, glued and screwed is a fine system as long as your joist depth, spacing and span meet the Tile Council standards.
If your last job held up fine, then I say go for it.[email protected]
It's Never Too Late To Become What You Might Have Been
I like your first plan ... if the 1x8 is in good shape.
Just glue and screw some 1/2" ply then install the 1/4 backer set in thinset.
If the 1x8 if iffy ... I'd bump it up to 3/4" ply.
I see no reason from here to tear up the existing subfloor.
I do recomment some sorta backer board.
I do plenty of tile work in older houses ... what kinda tile?
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
The 1x8 is good. It was originally nailed to the 3x8's but I will screw in down and replace any boards that are suspect.
I checked out the Schluter website. I have seen people mention "Ditra" while lurking on some threads. It still seems weird to "float" a solid floor but I really don't know much about the theory behind this. I have used concrete backer board and have faith in it but is this "new" method anything to think about or am I overthinking this whole thing - I tend to do that.
Thanks for the input.
One more question - Should I use any adhesive between the layers of wood or just screw them together? Once the tile floor is down I don't see any point in being able to unscrew one subfloor from the next. Or is it overkill to use some PL between the sheets?
I've always used yellow carpenters glue.
Buy a gallon and pour it on like maple syrup..............[email protected]
It's Never Too Late To Become What You Might Have Been
I just zip out what ever subfloor adhesive is cheapest at the time.
always the big tubes ....
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
CCI,It is definitely not overkill to glue between your 1x8 and your CDX. Doing so causes the two layers to act like one thick layer, as regards deflection, which is a good thing. The future guy who has to tear it out will utter some choice words about your maternal ancestry, however!I agree with Eric that CBU is oversold on floors. It is nice to work on, but not always essential. Although it does not add stiffness, it does add deadness, taking some of the bounce out of your floor sandwich.Bill
So I guess the best bet is to glue the 2 layers of wood and use concrete backer if I want. Does the thickness of the concrete board make any difference or is it just there to hold the thinset? I can easily get 1/4", 5/16", 7/16" and 1/2" thickness. If it does not matter I will use whichever gets me the easiest transition between rooms.
When thinsetting the concrete board to the ply does it matter which trowel and which thinset I use? I assume I want full coverage w/ the thinset but not a "bed" of it. Since the thinset will bond the 2 sheets do I space my screws further apart? I have both modified and standard thinset left over from another job. Does it matter which one I use and does it have a shelf life? It is about 9 months old but is not clumpy at all - can I still use it or is it best to start w/ fresh material for each job?
Thanks.
CCI,Yes, use whatever thickness of CBU that gives the height you want. The CBU just provides a good stable bonding surface. The thinset under the CBU does not need to be the modified, since its sole function is to prevent downward deflection by filling all voids between the panel and your plywood below.I usually use a 3/8" by 1/4" trowel for setting the CBU. This will work fine over the 3/4" CDX you will be using. Don't skimp on the screws; the thinset isn't holding the CBU down, just holding it from moving down under pressure. Mix the thinset under your panels kind of loose so the board can settle into it easily. Too dry can be hard to compress when screwing it down.The clump-free old thinset should be just fine. If you use it up laying your CBU, then you'll have fresh for the tile job, but it will do the tile okay, too.It is great to see someone who wants to do the job correctly. If major water was likely, you could apply Red Gard over your seamed CBU's, or one of the competing liquid-applied systems. They all do the same thing, which is to provide a water barrier that thinset will bond to. Hope this helps.Bill
Bill,
Have you ever used plain ole mastic to set the cbu? Cheaper both ends. Seems to work grea as far as I can tell.
CCI: If you dont want to use 1/2" cbu, try Hardi or something similiar. Any cbu that I have seen under 1/2 inch looks like it's ready for the dumpster before it even gets out of the store.
Eric[email protected]
It's Never Too Late To Become What You Might Have Been
Eric,I've never used mastic to set the CBU's, no. Do you use troweled mastic, or from a tube?I have never used 1/4" Wonderboard or Durock. Hardi is just so much nicer to work with in 1/4". I thought CBU was a term that includes Hardibacker; I intended to include it under the term. I do not like working with the 1/2" Hardi, and prefer Durock on walls. Wonderboard is less user-friendly than the Durock, so I used it before Durock came along. The rounded edges on the 5' sides make it much safer to handle.Bill
I use a 1/4 notch trowel.
Durock is a much nice product. I cut it with a diamond blade on an angle grinder.
I guess Hardi is included in CBU. I've never used it. Something about it I don't like. I can't put my finger on it.
Eric[email protected]
It's Never Too Late To Become What You Might Have Been
ditra is nice to work with.
way lighter than humping all that backer board where ever the job is. Lays nice and flat over the ply ... U also gotta thinset the ditra down ... same as the backer.
it "uncouples" ... the two surfaces ... if the subfloor is "iffy" ... it's a good idea. I like it over concrete basement floors ... as a precaution ... plus ... it'll span expansion joints.
over a strongwood floor ... I only upgrade to Ditra when it makes my life easier. Sometimes the more expensive materials saves labor costs and back pains in the end.
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
The Ditra looks like a good option since the bathroom is on the 2nd floor and I would be carrying the concrete board upstairs. I checked their website and it looks pretty easy to work with. I checked for local distributors and a whole bunch of Home Depots were listed in my area. I was at one last night and surprise, surprise the guy in plumbing/tile had never heard of it.
Do you have any idea what the cost is and if I can buy small quantities? The room is only 9ftx8ft and I don't think it goes under the shower pan.
I will try another HD but I won't hold my breath.
forget HD.
go thru the phone book and call some tile suppliers.
I can either order a roll of a coupla hundred sq ft .. from a couple places ...
or ... drive a bit out of my way to one flooring distributor that'll cut what ever I need off their big roll and sell me the exact sq ft. Their cut price is about double what I'd pay sq ft if I bought the big roll ... but ... since I only have to buy the quanity needed for each job it's a way cheaper buy in price.
I think last time I bought it in a small quanity I paid close to $3/ft sq. Might have even been more.
And you are right ... ditra does not go in a shower pan.
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
On your CBU question . . .
http://www.tile-assn.com/tileletter/pdfs/Substrate-Prep-0304.pdf
Seems to be recommended. I always use it on floors. Never had a failure.
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