Cement backerboard floor installation

I've read that the boards should be cut so they line up with the joists underneath the subfloor (similar to hanging drywall). I've also read that the minimum subfloor should be 5/8" of plywood, and that 1 1/4" screws should be used (also similar to drywall). The difference is that drywall is attached directly to studs, whereas with the backerboard, those screws won't make it through the 1/2" of backerboard plus 5/8" of floor (yes, 1/4" past, but not enough to justify screwing over joists.) Comments?
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that is correct all joints should end 1/2 way on joists otherwise there would be to much deflection where the backerboards meet causing it to crack.

that would depend on the floor joist spacing.

1 1/4" screws are usually recommended so you will not screw into a pipe or wire by accident. backerboard does NOT need to be fastened to the joists. the subfloor is fastened to the joists. the backerboard is fastened to the subfloor. the finished tile is fastened to the backerboard.
BTW personally I would rather install 1/2" backer board with thinset instead of screws. maybe a few 1 3/4" galvanized roofing nails (nailed into joists) to hold it in place until the thinset is dry.
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"Kitchens Inc." wrote:

Tile cementious or other composite tile or lino backerboard, underlayment, whatever the brand or thickness does not need to land on floor joists when placed over plywood.

Then you haven't read the mfg'er's instructions or installed very much backerboard. Thinset is good. Tile mastic is good. Nails or screws are mandatory.
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you are misguided there AnnG ALL sub flooring cementious or wood should always end on a joists whenever possible. besides it is "good practice"

I have probably installed over 3000 sheets or durrock over the years.

screws......you obviously have never installed durrock. they are the worst fasteners for installation. they just want you to purchase "their special screws"
galv. roofing nails I must admit are the BEST. but the thinset helps bond the backerboard to the substrate better.
mastic for a floor..........OMG never,never,never use mastic on a floor for anything. it is made for walls and ceilings ONLY. (as you put it) READ THE MFR'S INSTRUCTIONS
how much tiling have you done?
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"Kitchens Inc." wrote:

So? That doesn't make you correct. That only speaks to you either not knowing the superiority of mortar for substrates or you have no decent tile artisans in yoru area. Either way they are a substitute at best for mortar.

Like I said, read the mfger's instructions. I've never used screws for backerboard. Nails only. And btw, mastic serves the same purpose as the thinset for underlayments over plywood.

30 years or so. 4 crews doing primarily 500k+ homes and commercial floors. All counters, tub and shower walls are set over mortar. When certain job conditions dictate, tile backerboard is substitued for mortar on wood subfloors.
While tile underlayments are useful for wood subflooring tile substrates when elevation factors, etc, come into play; for the most part they are for use by happy homeowners and architects with no practical experience in the real world of professional tile setting.
3,000 sheets eh? And bragging??? I would stack my experience and quality up against yours any day of the week..
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sounds like we agree.....i think?

work must be good in your area. we have a lot in common you and I.

tiling is the easy part. configuring and foreseeing is the tough part.

you would have to work more years my friend to compete with my experiences. besides you are preaching to the choir AnnG (hmmmmm).
*pass the peyote*
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"Kitchens Inc." wrote:

I've no doubt you and I would get along great irl. I'm all for doing so here too. No offense meant and my appologies to you if it seemed so.
Hey were you ever around the Haight Ashbury scene in the 60's?
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I was planning on using both.
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jeffc wrote:

1/4" hardibacker is denser than the standard 1/2" 'other stuff' and eliminates elevation problems in many cases. Install it with either tile masti or thinsret and 1-1/4" galv. roofing nails. The joints do not need to land on a joist, however you're subfloor must be constructed properly, with all code specified material sizes, spans, etc, in place. http://www.ttmac.com/deflection_limitations.htm
Generally I would not advise a tile backerboard over 5/8" ply as a tile substrate. Perhaps another layer of 1/2" CDX followed by the 1/4" hardi, but it depends upon your subfloor construction as I pointed out
You might consider having a pro float a mortar bed substrate for you.
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1/4" galvanized roofing nails and hardibacker. I thought I would do it right and use screws. Even with the best auto-countersinking screws for backerboard, I could not get them driven into the hardibacker without drilling pilot holes and countersinking ahead. I went and bought the nails. With a nail every six inches in every direction that stuff is not going anywhere.
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