Replies

1. 
   JeffBuck | May 12, 2003 01:44am | #1

   recommended min thickness for the subfloor is 1 1/4".

   That's usually means a layer of 1/2 over the existing 3/4.

   That's for the subfloor structure. Backer board isn't structural......

   So the backer goes over the subfloor. 1/4 luan is about the worst thing U can stick under there.

   I know you're thinking about the additional height.

   I'd do no less than this for a customer where call backs cost money.

   If the floor is rock solid........I'd consider just overlaying 1/4 durorock...if it was my one house and I didn't care if it was half-####'d.....seeing on how the call back would be all my fault.

   Plenty of tile's been installed like that.....probably a 50-50 as to how long it stays put.

   I'd definitely skip the mastic for thinset mortar in either approach..and I'd go for a modified mastic if I was tempted to take the sub floor short cuts.

   Same with the grout...

   Then hope it doesn't crack.....too bad.

   Jeff

   Buck Construction   Pittsburgh,PA

    Fine Carpentery.....While U Waite                  

1. 
   SunnySlopes | May 12, 2003 04:59am | #2

   JZ,

      Jeff provided some good advise.  When he mentioned "Rock Solid" he meant it.  Not, well I feel a little bounce, but it's not that bad.  Do it right and you won't have the head ache of a cracked tile. 

     Normally when I do bathroom floors for customers I demo the entire floor right down to the joists and start there.  I then can re-enforce and level the joists and then glue and screw a new sub floor. 

      I believe at the very least you will need to rip up your old flooring down to the sub floor, then screw down your sub to the joists and then glue and screw down 1/2" ply on top of that.  Then install 1/4 backer with thinset, nail with roofing nails or screws, your choice.  Just don't nail the backer to the joists, just in the field of the 1/2" ply.   This will give you a solid base for your tile.  Use a marble saddle to meet the two floors and you will be just fine.  "One measurement is worth a thousand expert opinions"

1. 
   jz | May 13, 2003 12:41am | #9

   Thank you for your response. I appreciate your help. With all the other response, I know how I will replace my floor.

   Thanks again.

2. 
   CAGIV | May 12, 2003 09:16am | #5

   Jeff,

     Saw an add in this month's mag that had 7/8 ply, supposely 3.?? times stronger then 3/4. 

   Think you could use that with 1/4 ply and 1/4 cement board over it?

   Or if you were daring, maybe that with 1/4 cement over it if you were trying to deal with height issues?

   Just something I was thinking about, but like ya said I don't think cement board adds to much to the stiffness...

   Never be afraid to try something new. Remember, amateurs built the ark, Professional build the Titanic.

   Edited 5/12/2003 5:42:25 AM ET by CAG

1. 
   nino | May 12, 2003 05:39pm | #6

   The idea is to build the subfloor to minimum deflection tolerances. The thickness of the subfloor recommended  has to do with what is known to work in general construction and building practice and what you're likely to come up against. Of course if money were no object and you wanted to take the time, I'm sure that you could come up with many other ways to limit deflection within acceptable limits using a wider variety of materials.

1. 
   CAGIV | May 12, 2003 09:28pm | #7

   Nino,

     I understand that, but what I was wondering is if this 7/8 sub floor material is supposely 3 times stiffer, could you get away with the not using the additional layer of 1/2" on top

   Basically, as you said, what would be the deflection of the 7/8 Vs the 1 1/4 build upNever be afraid to try something new. Remember, amateurs built the ark, Professional build the Titanic.

1. 
   JeffBuck | May 13, 2003 04:26am | #12

   I've seen the same ads and had the same thoughts.

   Thinking it's a fairly new product...and probably not available everywhere....so I doubt the TCA has any stats on it's use. Pretty sure it's not in the soon to be replaced book.

   If I remember...I'll post our question on the John Bridges tile site and see what the everyday setters think.

   Me.....if it performs as stated....I'd be willing to test drive it.

   I'd not go lower than the stated minimums on a customers job.....as it may come back to bite me.....but many minimum standards are bordering on overkill. They take into account the crappiest materials to get to thos min's.

   I know for a fact tile can be thinset'd down.....regular thinset...not modified...directly over real lino.....which is glued over real 1/4 luan...the old water resistant stuff....over 1x6 diagonal subfloor......

   And...last for about 20 yrs....because I was about 15 when I helped my Dad do it in my parents entry. Still looks the same today. Not one hairline crack.

   House is right around 100 yrs old....I'd never consider doing that over similar materials/dimensions in a new home. Similar isn't the same.

   JeffBuck Construction   Pittsburgh,PA

    Fine Carpentery.....While U Waite                  

2. 
   jmarcus007 | May 13, 2003 05:03am | #13

   What is the "John Bridges tile site"? I Googled for it and couldn't find it.

3. 
   brianspages | May 13, 2003 05:21am | #14

   http://www.johnbridge.com

4. 
   nino | May 13, 2003 07:45am | #15

   I think as Jeff stated, it would be worth a try (and probably work too). One problem that I could see is if there was some sort of tile failure that was NOT related to the subfloor (grout flaking out, thinset providing insuficient bond, etc.) and you were held responsible because of using a subfloor that didn't fit the standard specs. I guess you'd still have to fix the floor anyway, but would you then be forced to take it down and rebuild the subfloor to the common standard?

   Edited 5/13/2003 12:46:37 AM ET by nino

3. 
   jz | May 13, 2003 12:39am | #8

   Thank you for your response. Along with the additional replies, I know how I should and will replace my bathroom floor!!!

   Thanks again for taking the time to respond.

2. 
   captbill | May 12, 2003 05:05am | #3

   Use harddiebacker instead of luan, if you have room use one half inch if not go one quater

1. 
   jz | May 13, 2003 12:43am | #10

   Thank you for answering my question. The responses have been very helpful. Thanks again..

3. 
   nino | May 12, 2003 09:04am | #4

   As a general rule, I too, demolish bathroom floors down to the joists. This is because invariably there is water damage to the plywood subfloor and possibly to the joists as well, especially in the area in and around the tub. Variances in flooring height from the bathroom to other areas isn't really a concern or all that much of a problem as you can use either a standard marble saddle or even a "Hollywood" marble saddle (sloped down on one side). The advice against both the mastic and the luan are  spot on.

   On another note and don't take it personally, are you asking your question because of a lack of know how or as a way of cutting a few steps in doing the job properly? I only ask because lately I've had some experiences in real life with homeowners wishing to do their own work on their homes willing to cut a few corners and compromising the job in order to save a few bucks.

    I feel that if you're not going to do the job correctly, whatever it costs you is too much to pay! Paying a few dollars more (whether hiring someone or doing the job right yourself) is worth it in the longevity and value of the finished project.

   Sorry for the little rant.

   
   

   ---

   Edited 5/12/2003 2:06:22 AM ET by nino

1. 
   jz | May 13, 2003 12:47am | #11

   Thanks for your response. This will help me do the job the right way. To answer your question, a little of both (inexperience and money). I'll bite the bullet and do the job as the responses have outlined.

   If I do a screwed up job, it can only cost me more in time and money to continually fix a problem floor.

   Thanks