Tried to find a good thread in the archives, but search didn’t work…again
Any way, here’s what i got:
We are going to tile the kitchen and dining room of our new home and I have never done tile work on anything other than a concrete slab. The joist are 2 1/2″ x 9 1/2 ” TGI’s on 16″ centers. The TGI’s sit on post and beam with the beams being no farther than 11′ on center. The sub floor is 3/4″ T&G plywood (glued). The tile with be an Italian porcelin 13″x13″
Can I use 1/4″ hardi backer or is 1/2″ needed? I would prefer the 1/4″ so as to keep the floor height in line with the rest of the floor coverings.
What is the correct procedure for putting down the backer board and can you incorporate some of the installation steps to speed up the procedure.
Or is it lay the backerboard with modified thinset, wait. Apply fiberglass tape, wait, then lay tile.
Is thinset specially designed for porcelin tile really needed?…what’s the difference?
Replies
You are OK for either tile or stone, but I would apply a membrane or CBU over the subfloor as suggested. Quarter inch Hardi, Half inch Hardi; or eight inch Ditra--either is OK. All should be embedded in unmodified thinset and nailed to the plywood, not the joists.
Then tile as usual. I would just use Custom Versabond myself.
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Why do you say to use unmodified thinset between the hardie and ply? Why not use the same thinset that will be used for the tile ... that saves on having to buy one more product, and probably have half a bag left over.
Whenever you are asked if you can do a job, tell'em "Certainly, I can!" Then get busy and find out how to do it. T. Roosevelt
Actually it depends on the manufacturer. Hardi likes modified under their boards. http://www.jameshardie.com/pdf/backer-install.pdf So does Durrock.
Utilicrete likes unmodified under their boards. I can't find a link to their instructions.
Ditra likes modified below, but unmodified above. http://www.schluter.com/english/products/2002/pdf/ditrahandbook03_04.pdf
For my money intuitively, there is a reason to use unmodified below and modified above. Modified thinset cures slower and is more flexible. Unmodified thinset cures faster. Because it is under a membrane or CBU, the latex is not needed. It is there only to add support to the CBU.
That being said, I like to follow directions and use whatever the manufacturer says to use. While I think the use of modified below makes no sense, most have now switched to modified above and below. Go figure.
Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Why would you not nail to the joist ? Do you feel you will hit a nail?Scribe once, cut once!
You actually want the CBU to sorta float on top of the plywood. By attaching the CBU directly to the joists, you risk too much movement. The plywood floor will move, but will move in unison. No telling about the joists.
Actually the most important reason is that the manufacturers say so. But there I go again.
Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
I've read other Ditra info that says to used the unmodified below and modified above ...
for the reasons U stated ... as the drying is different and moisture can be trapped ...
and ... I've also talked to a rep that said "they" recommend unmodified both above and below!
Last job I had my tile supplier call and check ... and they sent me all unmodified.
before that/not knowing ... I had used all modified ... and it's still doing well ...
I think I'm gonna start using unmodified below and modified above ...
maybe "they'll" figure it out by then.
as of a coula months ago ... I could get two different answers from different sections of their website?
btw ... anyone else bothered this guy's got only one layer of 3/4 ply? Not enough for me.
JeffBuck Construction, llc Pittsburgh,PA
Artistry in Carpentry
anyone else bothered this guy's got only one layer of 3/4 ply? Not enough for me.>>>
Free,
When possible I like using dbl 1/2". I think its much more stable than 3/4" alone.
Been wondering though lately about Advantech.
I've floored all the additions here in the stuff and it sure seems a lot more stable and solid than ply.
Wish someone would do an article about the comparrisons of substrates under tile and even the holdability (did I just make that word up...lol) of nails in different wood flooring typs such as Advantech. I even asked Piff and he didnt know...Now that is a calling for an article.
Be floored
andy
The secret of Zen in two words is, "Not always so"!
http://CLIFFORDRENOVATIONS.COM
take a run thru the John Bridges tile forum ...
I think advantec's been discussed there ...
JeffBuck Construction, llc Pittsburgh,PA
Artistry in Carpentry
I am working on a second story bath remodel, where the sub floor is 3/4 plank, it got swatches of roof felt to fix un-even joints, hardie backer,acrylic cement,(for water resistance) your floor should maybe get an acrylic "admix" in your thinset for water durability...Investigate your notch size on your trowel for the job you are doing, since, (sorry) I think you are a little novice at this ... LOL...
Scribe once, cut once!
I did a couple of rooms in 18" x 18" tiles. I used backer board, attached with screws and thinset. In the first room, I did the fiberglass tape at the same time, but ended up with a few high spots I had to know down before I laid the tile.
In the second room, I did the tape at the same time I put down the tile. It takes a little work not to scrape it off, but it was easier overall.
I used 1/4" CBB on mine.