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Unread 07-10-2011, 09:48 AM   #1
cx
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First time I've ever noticed Custom's requirement to use bond-breaker tape over plywood subflooring joints when installing Wonderboard. We could have a whole thread about that, eh?

Link To Technical Data Sheet for Wonderboard
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Unread 07-10-2011, 10:08 AM   #2
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I've always placed Duct tape over plywood joints so thinset dont get in there. got a pic of it on the thread I posted about SpiderWeb. Thought I was pose to.
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Unread 07-10-2011, 10:14 AM   #3
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Thought maybe somebody would take the hint and start this thread, but that didn't work, eh? So to prevent further confusion on the other thread I copied the initial comment here for discussion.
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Unread 07-10-2011, 04:54 PM   #4
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We should clarify sheathing and subfloor.

In my world sheathing is T&G installed with adhesive and attached to the joists with the proper nail or screw pattern.

Subfloor is an additional layer required for certain installations and should be installed per Frank Woeste and Peter Nielsen.

I trowel out a water resistant TB II or water proof TB III to secure subfloor to sheathing following proper fastening schedules.

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The subfloor shall have the proper rating,spacing, face grades and interior veneers. This is AC 5 ply 1/2" Fir from a lumberyard not the 4 ply crap from box stores. Never understood 4 ply with interior plies running in the same direction.

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I saw something earlier that the subfloor is never glued. Not in my world.
Adhesive beads? No. Full spread glue over a clean/prepped surface? Yes.

As far as taping the subfloor with proper spacing on top of sheathing would be a waste.
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Unread 07-10-2011, 06:01 PM   #5
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My understanding is that the first layer over the joists is subfloor, anything over that (and under the finished surface) is underlayment.

Can we get a link to the requirement, Kelly? Interesting. I never saw anyone treat the seams on plywood with anything.
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Unread 07-10-2011, 06:51 PM   #6
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Both customs and ardex reps have mentioned to me. If you fill with thinset then the edges have no where to expand. You might as well butt the sheets together.
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Unread 07-10-2011, 08:35 PM   #7
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Hereza link, Dan. I pewt it in the original post as well.

I've long been aware of lots of variation in regional terminology differences in the building trades. Tough to keep up sometimes, 'specially when you're on a global Internet site discussing methods and materials with people from all over the country and around the world.

The problem is sometimes exacerbated by some participants being from non-English speaking countries, such as Canada and New Zealand.

But to be moderately serious, I've never, ever heard subflooring referred to as sheathing, not from any part of the country. Sheathing to me goes on roofs and walls, usually exterior walls. Never on a floor. Not even in California.

Subflooring to me is at least the first layer of material that is connected to the tops of the floor joists. Any structural layer over that is also subflooring. Any material over the subflooring for the purpose of preparing for the final floor covering is an underlayment.

I wish I'd taken the opportunity to bring that up the last time Frank Woeste was on here with us. I have discussed with co-author Peter Nielsen the matter of their calling the second layer of subflooring an underlayment in their most excellent subflooring article. What they're installing there is subflooing. A second structural layer of subflooing. Specifically in preparation for the installation of an underlayment for the application of ceramic tile.

That's my take on the subflooring terminology.

As for the seams in the subflooring when installing tile underlayments, as I mentioned in opening, I've never noticed it being addressed by any manufacturer.

Just another good reason for us telling our visitors to always read and follow the manufacturers' instructions. Clearly ain't none of us gonna be able to keep up with'em all, eh?

[Segue]

For a really good time with construction terminology, get a group of framers from around the country together and axe'em to say the name of the vertical 2x piece closest to a door opening and supporting the end of a header.
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Unread 07-10-2011, 09:02 PM   #8
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Quote:
Originally Posted by cx
I've long been aware of lots of variation in regional terminology differences in the building trades.
I acknowledge my terminology is skewed.

AFATS I call that framing member a cripple or jack stud.
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Unread 07-10-2011, 09:03 PM   #9
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Quote:
Originally Posted by CX
Subflooring to me is at least the first layer of material that is connected to the tops of the floor joists. Any structural layer over that is also subflooring. Any material over the subflooring for the purpose of preparing for the final floor covering is an underlayment.
I agree with you here CX. I have always thought of underlayment as CBU, ditra, etc... and plywood as subfloor. In the TCNA 2011 hand book pg. 229 - the diagram refers to the second layer of plywood as "plywood underlyament."
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Unread 07-10-2011, 09:42 PM   #10
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Quote:
Originally Posted by Levi
In the TCNA 2011 hand book pg. 229 - the diagram refers to the second layer of plywood as "plywood underlyament."
Yeah, Levi, and I just hate it when they do that. But I think you've been around here long enough to see how much attention they pay to what I think, eh?

The only methods in there where they should call that structural plywood an underlayment are those where the tiles are bonded directly to it, such as F124, 143, 150, etc.

Let's hold our breath 'till they see the error in their ways.
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Unread 07-12-2011, 12:37 PM   #11
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Originally Posted by cx
But to be moderately serious, I've never, ever heard subflooring referred to as sheathing, not from any part of the country.
I guess I am not the only one that calls the first layer sheathing.

http://www.ownerbuilderonline.com/Bu...Sheathing.html

Back to the discussion. I read the pdf from Wonderboard and it makes sense to use bond breaker tape at the plywood seams.
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Unread 07-12-2011, 01:09 PM   #12
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I'd don't use much cbu and don't do many floors, but under slc, Ditra, or similar, I typically tape or caulk the upper ply layer joints to keep mortar out of there. Never agreed with the 'fill with setting material' language. When gluing down NobleSeal over ply with NobleBond, i let the glue go in there if it wants to.
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Unread 03-19-2013, 08:14 PM   #13
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Wall studs, roof trusses or rafters ,and floor joist's, are all covered by the means of sheathing. Anything that goes over that initial layer, can have numerous different attributes or designations.
On floor joists, it can be referred to as sub floor sheathing.

sheath·ing (shng)
n.
1. A layer of boards or of other wood or fiber materials applied to the outer studs, joists, and rafters of a building to strengthen the structure and serve as a base.
I totally agree with Chuck...
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Unread 03-19-2013, 08:47 PM   #14
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Welcome, Alberta. Please put a first name in a permanent signature line for us to use.
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Unread 03-19-2013, 10:41 PM   #15
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Once I used some cheap caulk I had in the trailer to fill the gaps between the sheets. I think I used ditra between that and the tile if I recall correctly.

Other than that I havent bothered. Not because I don't think its worth the effort, but because I don't have the opportunity.
Most of the time I am called just to install the tile. Most of the contractors I have done this for are not botherd to ask me what I would like done. They never leave a gap between sheets, ever. In fact they are pretty proud of "how tight we got those sheets together".
I'm not sure what the thinking is there, they do leave gaps in the rest of their sheathing

All the other tile guys here tile right over the second layer of plywood. The sheets are not installed correctly, and rarely if ever do I see anyone use an underlament.
So its not that I don't want gaps in the sheets, its just that I'm tired of beating my head against a wall. And it doesnt help that I don't have a failure to point to and say "see!"
Its just the way its done here because its been done so long that its the way its done here. Makes sense, except that it makes no sense.
I cant make sense out of that.. :uhh

I install the subfloor properly when I get to do it, which is almost never.
So how big of deal is this gap between the sheets thing? Shouldnt we be seeing a lot more failures here? Especially since its been done that way for so long?
My thinking is climate. Other places in the world have seasons. For a few months here its wet and cold, and then it gets cold and wet, then windy wet and cold, and then it repeats.
We don't have much for changes in temp/humidity, could that mean that there is not as much expansion contraction of the subfloor here in the swamp?

I donno, just curious how important the gaps are.
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