Prefinished hardwood flooring installation question

As a long time lurker and occasional contributor to this group I realize this may not be the correct to post this message but I'm going to do it anyway. :-)
I'm a competent amateur woodworker, http://bmacgillivray.ott.istop.com/woodprojects/projects.html and have done my fair share of home renovation projects but I've never installed hardwood flooring before. I've read up on it on a few web sites and perused the flooring book from the Borg and in all cases they suggest runing the flooring strips at right angles to the joists. Esthetically, this will not work in our house.
The current subfloor is 3/4" osb and is in ok condition. I read someplace that to install the flooring parallel to the joists an extra 1/2" plywood layer would be a good idea. Is this necessary or is is overkill?
TIA BMG
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On Mon, 10 May 2004 22:35:37 -0400, MacBain

consider a diagonal installation?
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Rule of thumb I was taught is it takes an 1 1/2 inch subfloor to keep ceramic tile from turning into dust, that said I think that even if you add the subfloor to build up to 1 1/4 I'm betting the floor would have some waves in it after some time. Maybe if you had access to the joists underneath you could add some solid blocking?
EJ
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The reason to run perpendicular is for the joist to bear the load. Is it over kill? Wait until you unload 300 sq.feet of 3/4" flooring and get a real feel for what is going to weight! We actually stacked some of our wood flooring boxes PARALLEL to the joists (like your proposed installation) and the plywood underfloor bowed and flexed! We re stacked perpendicular. Overkill- no. Architecturally correct- yes.
-- KB

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OSB is an unsuitable substrate for hardwood floor; doesn't hold the nails. An additional layer of plywoood is not only a good idea but necessary. Screwed and glued. 3/4" would be better in your application. Check the osb for flatness first.
Mike
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Definitely not overkill. Even if you were installing perpendicular to the joists, you should probably put down the extra 1/2" plywood. OSB does not hold nails well and when I was researching installation of flooring, all the advice I received said I needed at least an extra 1/2" of ply. I installed my pre-fin flooring at a 45 degree angle to the joists. Other than adding some extra subfloor, the installation of prefinished floor is a breeze.
-Rob

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Look at http://www.nofma.org/installation.htm (NOFMA: The Wood Flooring Manufacturers Association)
they state that 3/4 OSB is an acceptable subfloor. They dont specifically say it's ok to go parallel to the joists with that, though. I think it would be wise to add the plywood if going parallel to the joists...
david
MacBain wrote:

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