I am helping my son-in-law finish his basement. In FH #169, Andy Engel suggests putting down 1″ EPS boards under 2 sheets of 1/2 inch plywood. Two questions: Why 2 layers of plywood? Also, is EPS under plywood OK as far as building code or fire code?
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I'm not sure about the EPS question ( but I think it meets code)
But I think 2 layers of ply are used to give enough stiffness to the floor. haven't read the article in a while, but I would install the second layer perpendicular to the first, and make sure to stagger the joints.
If you send Andy an e-mail, he should get back to you.
You will need a minimum of 3/4" plywood for the floor. So, Andy uses two layers of 1/2" with the joints staggered. It's the easiest way to keep the sheets tied togewther without nailing to some kind of floor joists or sleepers.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Not sure about the EPS part but for decades I've always used 2 sheets of 1/2" ply with mastic between screwed to the joists. Better safe then sorry. Made for an incredab;y strong floor system
Now a days though I only use 3/4" Advantech. That stuff is bulletproof.
Be well
andyC
The secret of Zen in two words is, "Not always so"!
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Hi Art. The other guys answered the plywood question as well as I would have.
As to the foam, there was no problem with the local inspector. Its bearing capacity exceeds the live loading requirements of the IRC by an order of magnitude. The other problem you might encounter is flame spread. The inspectors I've spoken with have had no problem with that issue. However, among the hundreds of emails that I received regarding that article, one fellow did have the inspector balk for that reason. If yours does, you could address the concern by laying down a layer of 1/2 in. moisture resistant drywall between the foam and the plywood. I haven't tried that mind you, but can't see why it wouldn't work.
Andy
Andy Engel
Senior editor, Fine Woodworking magazine
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Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
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or cement board instead of the drywall
but if a fire's gonna get thru the ply to the foam, it's most likely too late, anyway
Yeah, that was my take too.
I like your idea better than the drywall.Andy Engel
Senior editor, Fine Woodworking magazine
An updated profile is a happy profile.
Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig
None of this matters in geological time.