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Discussion Starter · #1 · (Edited)
My husband and I are about to install our Hardie backer down today for our kitchen remodel. We had been previously gutted down to the floor joists due to mold. Mold is treated now. We installed 5/8 inch OSB subfloor, and now, we're planning on throwing down thinset mortar and Hardie backer boards. Our final plan is to tile on top of the cement boards.

Not sure why we didn't go with 3/4 inch OSB, but the 5/8 inch is down now and all secured. Will 5/8 inch plus cement board be strong enough for kitchen flooring?
 

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Discussion Starter · #2 ·
Oh, and by the way, why does the website for my dry mix thinset mortar say we shouldn't apply directly onto plywood or OSB board???? Should we have some sort of underlayment too. I haven't seen anyone talking about that yet...
 

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Tileguy
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Will 5/8 inch plus cement board be strong enough for kitchen flooring?
Probably be almost okay. You have chosen to deal with the minimum of the minimums using the 5/8 OSB. The cement board has and offers NO structural value what-so-ever. If you use porcelain tile you might be (I said "might be") okay.

why does the website for my dry mix thinset mortar say we shouldn't apply directly onto plywood or OSB
Because they don't want you installinmg tile directly to plywood or OSB!!!

Not sure why we didn't go with 3/4 inch OSB, but the 5/8 inch is down now and all secured.
Oh well what's done is done it'll be okay, doesn't really matter what the industry recommendations are I guess.
Not sure why we didn't go with 3/4 inch OSB,
You did that because IT WAS CHEAPER and you want to re-do the floor in six months.:yes:
 

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Discussion Starter · #4 ·
Awwww, Bud Cline - Tile Guy, you're killin' me. :laughing: Do you really think we'll be redoing this floor in six months??

We didn't go with 5/8" because we were cheap. Somehow, my husband settled on this when he was doing all his DIY research. We were trying to consider all the height requirements with consideration to the subfloor, thinset, cement board, and then porcelain tile. We don't have one of those fancy, high ceiling homes -- we're trying to end up with 8ft. of floor to ceiling space.

If you really think that what we're heading for complete and utter failure, then I'll have to come up with some way of breaking the news to the ol' husband before we lay the cement board. I don't think this marriage will bear the weight of cracked tiles. :bangin: HAHAHAHAHA!

Short of tearing up what we have so far, do you have any remedies?
 

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Tileguy
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What is the size of the floor joists?
What is the species of the floor joists?
What is the spacing of the floor joists?
What is the unsupported span of the floor joists?
:)
 

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Discussion Starter · #6 ·
Floor joists are 2x10

Don't know what species, but 4 contractors told me they were in great shape (original/only previous owner was a builder by trade; house custom built for his family in 1961). He actually even took the time to stain them (according to one GC).

Joists spacing is 16 inches from center.

The unsupported span from exterior wall of house to center, steel I-beam is about 11 feet.

Why is there is no icon for fingers crossed? Well, at least there's one for sweating... :sweatdrop:
 

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Tileguy
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Okay you have a typical situation and one that is better than some that come here. Just keep in mind that your typical situation is also one of minimal effort on the part of the builder. You are dealing with minimums and the 5/8" subfloor isn't helping.:laughing: Okay now you have been officially scolded.

What you want to do is do-able. If it were me (and it's not) I would forgo the cement board and use Schluter DITRA XL for the tile backer.:)

Good luck.:)
 

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Discussion Starter · #8 ·
Okay, I'll look it up and look for it.

Thanks for your time, Bud Cline -- Tile Guy!! :thumbup: heehee..these icons are silly.
 
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