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-   -   Plywood thickness: asked for 1/2" plywood; hardware delivered 7/16 (.437) thickness) (http://www.diychatroom.com/f5/plywood-thickness-asked-1-2-plywood-hardware-delivered-7-16-437-thickness-67810/)

lazzlazz 03-28-2010 08:29 PM

Plywood thickness: asked for 1/2" plywood; delivered 7/16"; granite tile questions
 
newbie here ...
I know solid wood products are slightly smaller than stated dimensions but I thought plywood, since it's engineered would be the declared thickness.

If I asked for 1/2" plywood (and paid for 1/2") and hardware delivered 7/16 (.437) thickness, did they deliver what I paid for?

I had previously ordered 3/4" for the subfloor; I just measured it and it's also 1/16 inch short of 3/4 inch. So maybe the hardware is right?

I'm putting in tile & need to match to some of the old subfloor & these two 1/16" differences are adding up to a big problem.

I had the hardware cut one of the two sheets in half; if the hardware is wrong, I'm sure they'll take it back; if I was wrong, they will probably take back the uncut sheet, but I'll be stuck with the cut sheet.

oarfish 03-28-2010 08:32 PM

That is pretty standard sized lumber you have received.
Try using it and dealing with the 1/16 difference may not be an issue for you.

lazzlazz 03-28-2010 09:00 PM

Thanks ... this difference is 2 x 1/16 inch, since both the 3/4 inch and the 1/2 inch plywood is 1/16 inch thinner than I thought. Plus, there was an existing roughly 1/16 inch difference between the remaining old subfloor/underlayment & the new subfloor/underlayment that I was just going to try to deal with by using a little more thinset.

Now, I'm ending up with 3/16 inch difference between the remaining old subfloor/underlayment & the new subfloor/underlayment. I'm putting in granite so I'll end up with cracked tiles if I ignore it.

I guess I'll have to build up the difference. I looked into using the Schluter-Ditra XL, which is thicker than the Schluter-Ditra, but I need only about 1 roll of the S-D (55 ft2) and the XL is sold in rolls of 150 ft2. Plus, I'd still need a few square feet of the S-D for the existing subfloor.

Any suggestions on the best way to build up the difference? I guess one way would be to mix up some self-leveling compound and build up the whole new area. The advantage is the floor would be level. Any thoughts on pros/cons of this, or better options?
============
Or - I could abandon Schluter-Ditra and use 1/4" cement backer board (Durock? I think hardie-backer is my only other option within 80 miles and the comments on that have been less favorable than for Durock). Thoughts?

(By the way, I ripped out the old floor, which consisted of 2 layers of pieced-together OSB (some as small as 18" square) & 1/4 inch plywood ... amazing how much more solid just the 3/4" plywood (even without the underlayment) once it's screwed down to the joists. I may not know a lot of things, but nothing I can do can be anywhere near as bad as some of what I've found! This site has been helpful for me figuring out what is right ... this site made me decide to rip out down to the joists.)

JazMan 03-28-2010 10:57 PM

Hi Lazz,

Measure that again. All plywood is 1/32" thinner (not 1/16"), than it's stated thickness, has been for years. Not sure what you're doing exactly, but maybe some tarpaper between thesheets will do it for you.

Stay with Ditra if at all possible. I use regular Ditra all the time. You might find someone that can sell you some by the ft.

Jaz

lazzlazz 03-28-2010 11:27 PM

Quote:

Originally Posted by JazMan (Post 421019)
Hi Lazz,

Measure that again. All plywood is 1/32" thinner (not 1/16"), than it's stated thickness, has been for years. Not sure what you're doing exactly, but maybe some tarpaper between thesheets will do it for you.

Stay with Ditra if at all possible. I use regular Ditra all the time. You might find someone that can sell you some by the ft.

Jaz

Thanks for the advice. I'm quite "rural" (N IA; 1.5 hours from the nearest Home Depot/Menards) so options are fewer but I'll see if any of the tiling/home remodeling guys in town use the Ditra - it's possible.

The plywood the hardware delivered as half-inch is stamped .437 inch underlayment (Boise, from Louisiana), and that's 7/16 inch thick (I checked on the calculator). It's the one-face-plugged stuff to go under the Ditra - do you lose more in the finishing than with rougher plywood?

However, the stuff delivered as 3/4" is also 1/16 inch short on my ruler (nothing stamped on).

Another thought would be to install radiant floor heating! That would involve calling an electrician because I think I'd need it on its own circuit (I might actually have room for one - there are some spaces at the bottom of the circuit box). This would increase cost, work, and headaches in general - but if it worked, would be nice.

Daniel Holzman 03-29-2010 12:29 AM

I too have been puzzled by plywood thickness. I build my own cabinets, and early on I discovered that some hardwood veneered plywood sold as 3/4 inch is in fact 1/32 inch thinner, while other veneered plywood sold as 3/4 inch is exactly 3/4 inch. There are also metric plywood sheets that are slightly different than English unit sheets. As a result, I have accumulated a collection of router bits that are exactly the thickness of the various types of plywood I work with.

The only way to know exactly what thickness plywood you are going to get is to check the specifications before you buy, or carry an accurate gauge with you when you go to the store.

lazzlazz 03-31-2010 10:52 AM

I just talked to the hardware and they tell me the manufacturers are now shipping as 1/2 inch plywood that is stamped .437 (7/16); same for 3/4" (it will be 25/32); this seems to be the case for underlayment plywood stamped Boise. Lesson learned. 1/16" differences start adding up when you're supposed to have 2 layers of plywood under tile - plan for this to meet the "minimum" thickness required under tile. I was planning an extra 1/8" over the recommended (now I'm just at the recommended). The bigger headache is I'm not matching up in height to the existing subfloor/underlayment.

47_47 03-31-2010 12:25 PM

deleted can't add today


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