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Discussion Starter #1
I'm trying to do my first bathroom remodel and I'm getting stumped on the subfloor. My joist are 2x10 10' span 16" oc not sure of the kind of wood with 5/8 plywood subfloor. From reading james hardie site this is enough and to use 1/4 hardie board. But one big box store agreed and 2 said I need 1/2 hardie board. Any help to point me in the right direction would be
appreciated . oh and I'm using 12x12 porcelain tile
 

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Stuck in the 70's
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First, few apron store people really know what they're talking about. You might get lucky and find one, but how do you really know? Shoot, maybe the two you talked to were experts on plumbing. That ain't gonna help you with your tiling project, is it?

Second, I don't really know what I'm talking about either, but I've been hanging around here for awhile and have picked up a few things.

When I did my tile projects I read a lot of the old threads here. I dug through them and figured out which posters here really knew what they were talking about and followed their advice.

FWIW, (and what I've read here) a thicker hardie board will not add structural support. 1/4" is used on floors, I'd stick with it. As far as whether your subfloor is adequate for tile, I will leave that for someone else.
 

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NACE Coating Inspector
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i over hear bad advise in those stores all of the time. i just dont get why people listen to someone that is obviously guessing about the answer.
 

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Stuck in the 70's
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I don't want to bash people who work retail. Heck, I work retail! But consumers should realize that if you shop at one of those big box apron stores there are a whole lotta different departments under that one roof. Off the top of my head: Insulation, plumbing, electrical, lighting, lumber, flooring, tiling, kitchen cabinets, appliances, lawn & garden, etc., etc., etc.

If you're shopping there and you expect everyone working there to have knowledge of every department and every product.......
Well, you need to up your medication.

Edited to add: Sorry, Nascarnut, I didn't mean you need medication. Just venting.
I'm still hoping someone else will come by and help with your deflection question.
 

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Tileguy
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Hi All,

From reading james hardie site this is enough and to use 1/4 hardie board. But one big box store agreed and 2 said I need 1/2 hardie board. Any help to point me in the right direction would be
So, you have the 3 big box stores in your area? Too bad, that's worse then having only 2. :laughing:

The Blonde in correct, in that 1/4" is made for floors, however you can also use the 1/2", but only if you need the extra height.

Your joists spanning only 10 ft. is good, I'm not so excited about the 5/8" subfloor though. It scares me, but the manufacturers claim it's good enough, as long as it's in perfect shape of course. Can you add a layer of 3/8" or thicker?

Jaz
 

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Discussion Starter #6
thank you for the replies. JazMan I don't think I can it is a 1/2 bath that goes into a hall way with a kitchen at the end, it is all vinyl with 3/8 underlayment. So if I put down 3/8 plywood thinset 1/4 hardibacker thinset tile, won't that make the transition to high? I did remove the vinyl and underlayment in the bathroom.
 

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Tileguy
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So if I put down 3/8 plywood thinset 1/4 hardibacker thinset tile, won't that make the transition to high? I did remove the vinyl and underlayment in the bathroom.
This comes up all the time. There's nothing more frustrating then hearing people want to use 3 different types of flooring in their homes, but still want all to be close to the same level. Even to the point where the level seems more important then a proper installation.

If people want the floors in their homes to be the same level, simply install the same flooring in every room. Easy. From what I understand the difference in this case may be about 5/8" after the Hardie and tiles are installed. No problem. You can save another 1/8" by using Ditra instead of Hardie.

I have found a rise of even an inch or a bit more is very manageable in residential work. I may not recommend that in a commercial situation, since people are not familiar with the floors and do not expect sudden change of elevation. Then you have those that are looking to take a dive.

Jaz
 

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Discussion Starter #8
thank you for the help

I wasn't worried so much about matching but about being a tripping hazzard. So I'll add 3/8 plywood and probalby go with the ditra. Does the ditra take a special mortar?
 

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Tileguy
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Does the ditra take a special mortar?
Not really special. There's two basic types of thin set mortar, unmodified and modified. You use a modified to install Ditra since you're going over plywood. Install any tile (except glass) using a premium unmodified. Yes unmodified, even if it's porcelain ceramics. What are your brand choices?

Jaz
 

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Hardi backer board

I have not seen the question answered. Does hardi backer board need thin-set between it and the subfloor? Or can you just screew it down?
 

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Hardie needs to be set in a bed of thinset---This is there to fill voids under the backer----

Hollow spots under the backer are a big cause of tile failure,especially with Hardie backer--it's so stiff that it bridges low spots more than Wonder Board or Durrock.
 

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Civil Engineer
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I used Ditramat in my kitchen stone tile installation, and I was very pleased with it. It does add extra cost, and increases the complexity of installation due to the need for two different types of mortar as JazMan discussed. Prior to finishing the design, I strongly suggest the OPS visit the Schluter website (www.schluter.com) and read the articles regarding subfloor stiffness, adequacy of your joist condition for 12 inch porcelain tile, and installation procedures.

Ditra is a bond breaker and water resistant layer, not a structural element. Only about 1/8 inch thick when installed. However, if the floor is not stiff enough, you may crack tiles. Check their section on stiffness carefully, the larger the tile the greater then chance of cracking a tile. You may want to think about smaller format tile, like 6x6.
 
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