Marble tile and sub-flooring


  #1  
Old 11-06-05, 09:06 AM
C5Bud
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Marble tile and sub-flooring

Hoping to install marble flooring in upstairs bath remodel. Flooring is 2x10 joist, 16"oc with 3/4" TG plywood. Original floor added 1/4" luan and ceramic tile to that - no problems.
Tile store recommends 1 1/4 sub floor so plan was to strip the luan and add another layer of plywood - however local yards don't stock exterior grade. (?) Lowe's recommended 1/2" Hardiboard to give 1 1/4" total - they claim it will be fine, but...

L shaped master bath - longest run along the joist - 4 1/2'w x 9 feet, but supported by a perpendicular wall downstairs at the 5' point lengthwise - this span may also have extra reinforcement as it holds double wide Jacuzzi tub. Long span across the 18" joists is 12' across - with no walls below. Any thoughts from the real world on subfloor requirements?
 

Last edited by C5Bud; 11-06-05 at 09:23 AM.
  #2  
Old 11-06-05, 10:43 AM
chrisnoblesfloo
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mud down and screw or use roofing nails to 1/4 or 1/2 backer board and make sure you follow the directions on nail pattern. This should suffice.. I have 4 houses that we put marble in and they are all fine 6 years old..
 
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Old 11-06-05, 05:05 PM
JonBurrows
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I am no expert, but I was under the impression that Hardibacker offers no structural stregnth and is simply to provide a clean and sound base for tile. I thought you get to the magic number of 1 1/4" plywood (a/bx no CDX) and THEN put 1/4" hardibacker ontop.....
 
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Old 11-06-05, 08:11 PM
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You are right Jon
 
  #5  
Old 11-07-05, 11:05 AM
C5Bud
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Appreciate the input. Returned to the specialty tile store today and they assured me that with the 1/2" Hardiboard I would have the magic 1 1/4" and be good to go. Spoke with the Hardi guys and they assure that it is not structural - does not add strength. Sounds like it's time for the coin toss.
 
  #6  
Old 11-07-05, 11:16 AM
JonBurrows
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Sounds like your looking for the answer you want to hear to me.....
 
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Old 11-08-05, 04:28 PM
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Sounds to me if the manufacturer says it adds no strength, then you need to go by what James Hardi says. (BTW, no backer offers any strength, just gives a more stable bonding surface) Every lumber yard stocks exposure 1 plywood which is exterior rated. You want bc or better graded plywood. How long do those joists span between supporting beams/walls? And be very wary of any advice you receive at a home center. Experience and knowledge are a rare find at one of them.
 
  #8  
Old 11-12-05, 07:40 AM
C5Bud
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"Sounds like your looking for the answer you want to hear to me....."


Actually I ask questions to gather information - and usually persist until a concensus emerges. So far, all the info I have is conflicting and I was hoping to hear the voice of experience. The big box clerks assure me that 1/2" cement board is the way to go, Best Tile, the pro retailer where I'm actually purchasing the tiles, also says its fine. Comments on this board suggest otherwise - but there is no common thread. Industry sources don't want to be responsible, just covered.

Called a former American Olean VP this week and he went blank on the cement board issue - he had departed before Hardi gained a meaningful presence. He suggested I check my other floors - where I find 400 sf of 12" ceramic over the 3/4 and 1/4 luan - and only one cracked tile in 1989, and the repair has survived intact. Guess I'm eventually the voice of experience on this one.
 
  #9  
Old 11-12-05, 08:22 AM
JonBurrows
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Cool

As I said before I offer no tile experience and come her for guidance and suggestions. I do so because I have worked in retail management for years and can assure you that a Home Depot associate knows nothing more than you or I and what he purpourts to know like an expert he has learned through his home study of the "vendor-specific e-learning modules". A few weeks working the plumbing department will get him a transfer to home and garden the following week where he will gladly act as a master gardner until he is transfered to lumber where suddenly he becomes a deck expert selling the virtues of trex.

If I have learned anything from reading this board and Johnbridge it is this, "min. sub floor of PLYWOOD screwed is one and one quarter inch. Follow that with 1/4 cement backer board nailed or screwed to floor field with thinset undder board, do not nail or screw cbu to joists. This is based upon joists being 16 o.c. and with a deflection of L350 or better for ceramic and L750 for natural stone (marble included). Thats off the top of my head and I must read it 2x a week... Basic floor prep 101 before you even think of tile.

You can talk with 100 guys from HD and get a 100 different answers. But talk with 100 PRO's who do this for a living and ask what they pu down on their own floors before tiling and I bet you 85% of them would tell you the same thing...

I know the feeling of staring at a floor and saying, either I do it right and rip it out.. when I know all the homes I have even lived in just went onto the ply (explains the reason a few tiles had hairline cracks).

Bottom line is... either do it right now based upon pro experience ,or listen to the Home Depot garden/lumber/tool/plumbing/electrical expert and take the chance of it cracking later.. I'd put my money on the pro....

Ever wonder why a guy with so much tiling experience is working full time at Home Depot for $9.25 an hour... must be between tile jobs I guess....
 
 

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