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Unread 10-02-2006, 05:57 AM   #1
jayathena
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Travertine.

What do I need to do? Is there a "I Didn't listen to the deflect-o-lator, therefore my tiles are cracked everywhere" thread?

I just spend 3 back breaking weeks beefing up my unlevel floors of an old house. We put 2x8 pressure treated joists every 16" and secured 3/4" plywood over the entire floor. We doubled the outer perimeter with two 2x8 pressure treated and then used the buckets for the joists. I think the joists are about 9' long.

I bought 23 sheets of 1/4" hardibacker, mortor for underneath and 33 pounds of flat head (roofing?) nails to secure.

I want to install 18x18 Travertine honed and filled with 1/8" grout space, staggered (hopscotch).

Is it really going to be a cracking tile disaster? Will I really be back here saying, "You were right?". I am at the end of my rope and then run across this deflecto-lator thingy.

Would adding a layer of 1/2" plywood over it before the hardibacker work?

jason
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Unread 10-02-2006, 07:30 AM   #2
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Welcome, Jason.

Prolly easier to just slit your wrists and bleed out where you stand.

Naaa, it ain't that bad.

But your joist structure needs to meet L/720 deflection standards for a natural stone installation. Likely the easiest way for you to achieve that would be to sister your existing joists. The fact that you used treated wood is gonna be problematic, unless it was KDAT. Don't like to see that full-wet stuff used anywhere a tile installation is to take place.

You could also add a beam under the existing joists to shorten the span if that would be easiest in your situation. Again, you're gonna have long-term problems because of the shrinkage of that PT wood.

And you must add a second layer of plywood for any stone intallation. The minimum thickness is 3/8ths-inch, but I prefer half-inch. Install it according to these guidelines.

My opinion; worth price charged.
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Unread 10-02-2006, 07:52 AM   #3
jayathena
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First, I know and understand the proper answer, ugh. With that said...

concerning Cracking of Floor Tiles, using existing subflooring as described above..

Will all my tiles crack like crazy immediatly or will they be alright for certain period of time and then cracking in the future? And even so, will it be a few here and a few there, or the entire floor?

and, is there a small possibility that every might be ok as is? Has anyone out there broken the rules with success?

Just weighing my odds...
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Unread 10-02-2006, 07:56 AM   #4
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Hi Jason,

Don't mean to pile it on, but I would go so far as to tell you to wait at least six months before installing tile or stone over the pressure treated lumber. That's if it's the regular old wet stuff, not kiln dried after treatment.
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Unread 10-02-2006, 08:05 AM   #5
jayathena
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ahhhhhhhhhh.. What if I change out my travertine for ceramic? Do they make a nice travertine look alike ceramic?

thanks for your time.
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Unread 10-02-2006, 08:59 AM   #6
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Hello. I am another DIY'er. Be glad that you found out about the deflecto when you did. I didn't know about the deflecto until I had already passed the point of no return. I'm not exactly sure what my true deflecto really is (and I'm afraid to ask). Some of my joists are already sistered. I'm about half way done with my floor- travertine. Good luck.
Stephen

Last edited by SRPACE; 10-02-2006 at 09:11 AM.
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Unread 10-02-2006, 09:02 AM   #7
jayathena
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keep me informed of your progress and issues. i would love to hear some disaster stories but i can't seem to find any.

jason
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Unread 10-03-2006, 05:24 AM   #8
jayathena
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Little more cooled down today... Please understand my frustration and denial... After spending so much time thinking I was doing the floor properly then I find this Deflect-O-Thing.. Extremely frustrating since I was ready to move on with my drywall / tile / complete the room....

anyway..

I decided to, this weekend, climb under the house and put some support beams across the floor joists 1/2 way point. One room is about 10' joists, so 5' is the joist. Second room is about 9' joists, so mid point is about 4.5'....

I have NOT added to beams yet... and read somewhere to do a bouce test with water.. I filled a glass of water in different parts of the room to the very rim (could not pick it up without spilling it) and bounced all over the floor like an idiot. NO water spilled at all. I am shocked this is not enough support, espically if a pro puts the tile down properly with mortor bed, whatever...

My deal again:
2x8 joists every 16", about 9-10' length, 3/4" plywood screwed like every 3 inches. Then plan to put mortor, 1/4" hardibacker.
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Unread 10-03-2006, 06:48 AM   #9
cx
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Quote:
Originally Posted by Jay
My deal again:
2x8 joists every 16", about 9-10' length, 3/4" plywood screwed like every 3 inches. Then plan to put mortor, 1/4" hardibacker.
My deal again:

That floor structure meets minimum deflection standards for a ceramic tile installation, although many pros would still require you to add additional plywood.

That floor structure does not meet minimum standards for a natural stone installation, especially between the joists, and you must add the second layer of plywood before the CBU.

Or, of course, since it's your house, you can install the stone as you had planned and let us know how it works out in a year or so.

My opinion; worth price charged.
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Unread 10-04-2006, 12:07 PM   #10
jayathena
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Double Layer of Plywood & Seams

I have searched and can not find a straight answer on this question.

1. What exactly is the purpose of the double layer of plywood? Is it related to deflection?

2. What type of tape (from a Home Center) should I use on the seams of my Hardibacker Board? Can I just use drywall tape?

thanks!
jason
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Unread 10-04-2006, 12:29 PM   #11
sgrandjean
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Jason,

The double layer of plywood gives you a decent subfloor to tile on. It is important that the amount of deflection in your floor joists over the longest unsupported span is such that it meets minimum requirements for ceramic or natural stone. You can plug numbers into the Deflecto (on the blue toolbar above). I'd use fiberglass tape for your hardibacker seams and then mud them with thinset. If you have further questions related to deflection, reply to your thread and maybe we kin direct some more knowledgeable souls in to answer your questions.

Cheers.
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Unread 10-04-2006, 12:30 PM   #12
Dave Taylor
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Jason...

A double layer of plywood is a standard for a stone covering and is used for deflection and un-coupling. It helps reduce deflection and assists a CBU or membrane's un-coupling capabilities.

This is an oft repeated requirement from ALL of the stone pros on this TYW Forum.... but I don't know if any collection of posts that relate to this subject have been compiled and indexed here. Mebee someone else knows.

When taping Hardi seems use either Hardi alkali resistant fiberglass tape or USG's offering. HD and Lowes here-a-bouts carry both. Do not use standard drywall tape to tape and mud Hardi seams.

Hope this helps

I see Scott is quicker than me. Jason, I'm referring primarily to deflection present between joists.

Also your previous posts indicate to me that you are using travertine.... a stone product.
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Unread 10-04-2006, 12:58 PM   #13
tiffer
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as i understand it, a single layer of plywood will be, at some point ended at one of the joists, as the ends of the plywood create a "break" in the floor covering, there will tend to be more deflection here than where the plywood just passes over a beam mid-panel (immagine the plywood is a multiple span beam, with supports at each joist ...... the second layer of plywood makes the entire floor react as a continuous beam instead of a series of shorter beams) (sorry its difficult to describe what I'm seeing in my head)

got a quick drawing here ...hope it helps .....sorry it's not very good
Attached Files
File Type: doc 2ply-1ply.doc (19.0 KB, 179 views)
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Unread 10-04-2006, 01:06 PM   #14
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excellent! That makes a lot of sense... thanks!
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Unread 10-04-2006, 10:00 PM   #15
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plywood

The reason for two pieces?

Really, the reason is that its easier, and less expensive to install 2 thicknesses of plywood to achieve 1 1/8" of underlayment, than to just install 1 layer of 1 1/8" plywood. The single layer of tounge and groove is way stronger than the double layers.

Oh, and probably because it wasn't even manufactured until a few years ago.

GP Plytanium T&G 1 1/8" Cool stuff.
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