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I will be installing some 3/4″ maple flooring (Bruce) and am wondering about whether or not I should use red rosin paper underneath. My house is built over a crawl space. I have put down 6 mil poly over the ground, and a layer of 30# roofing paper between my sub-floor and underlayment (3/4″ t&g OSB).
Also, the manufacturer reccommends a 3/4″ gap away from the wall for expansion. I have an 8′ sliding glass door that has a plastic sill. Can I run the maple right up to the plastic sill at the door, or do I need to maintain a 3/4″ gap there also?
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John - I'm no flooring expert but I have installed a few thousand feet. I don't like the sounds of relying on OSB to hold those flooring nails. The only way I'd be comfortable doing that would be using nails long enough to penetrate the plywood subfloor. (that isn't Comply or OSB too, is it?)
Hardwood floors swell and contract more across the width of the boards so your question about the SGD depends on whether you will have end grain against the door or the edge of a board there. I wouldn't worry about another layer of paper, but someone else probably knows better than I about that. - jb
*We've always used the red rosin paper. I think the theory is it reduces squeaks and acts as a slip sheet for the flooring to expand and contract. Jim 's got it dead right, end grain no sweat, sideways , follow the mrfr's recommendations. Use some type of Maple molding to bridge the 3/4, even if you have to rip your own. It'll look good against the high threshold of the slider too. I don't know about the OSB, but you can increase your nail pattern if you have doubts about the holding power. If you are already into the heating season and yuo've turned on your furnace, watch the humidtiy, don't let it get too low, try and keep it around 40% rel. If you really shrink the wood before you put it down, it's going to really expand if you have a damp climate.Jim can tell you what humidity swings can do to wood, but most people don't believe it. If you heat with wood, think about a humidifier. Your floors will thank you and so will your family.. .. Actually, no matter what you heat with, most houses get way too dry in the winter in cold climates.
*are you sure about the 3/4 expansion? sounds like a lot.
*Jim,I checked with the manufacturer prior to laying the OSB. They said OSB is fine, as long as it is PS2-92, whatever the hell that means. I made sure that the OSB I used had those numbers on it. The door will be along the side of a floor board, so I will follow the mfr's advice and leave a 3/4" gap. Now if I can only find the right reduction moldings, I'll be OK. Thanks for the input !
*I know a lot of you guys don't like OSB, but for what it's worth we have put quite a few HW floors over 3/4" OSB and we have never had any problems. One difference may be that we haven't ever let the OSB get wet.
*Thanks Nick.......it's nice to hear that I haven't made a terrible mistake in choosing OSB.
*Nick - I like OSB ok for sheathing, especially with the type of CDX we are getting anymore, but it just seems questionable to me about it holding a nail. Probably just my old predjudices rearing up again. Feel better about it now that you've vouched for it. - jb