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        posted
        does it matter which way the subfloor runs before new 3/4" hardwood flooring is installed?
         
        Posts: 2 | Registered: Jan 09, 2014Reply With QuoteReport This Post
        Picture of Jaybee
        posted Hide Post
        The first layer of subfloor is a T&G product. As such, it's 8' length will run in the opposite direction as the joists. This will allow the T&G to give support to the 14-1/2" span between joists. If a second layer of subfloor is added on top of the first, it can run in any direction as long as the seams do not line up.


        Jaybee
         
        Posts: 10363 | Location: Knoxville, Tennessee | Registered: Sep 27, 2003Reply With QuoteReport This Post
        posted Hide Post
        "it can run in any direction as long as the seams do not line up".

        I don't agree. Any additional underlayment should also run perpendicular to the joists. That is the orientation in which ply and OSB are the strongest. Just offset the seams as much as possible of course.

        Jaz

        This message has been edited. Last edited by: JazMan,


        Tile 4 You llc - Troy, MI
        Kerdi shower specialist - Ditra installs - Product-Method suitability consultation. I have NEVER made a mistake, I thought I did once...........but I was wrong!
         
        Posts: 47 | Registered: Apr 18, 2013Reply With QuoteReport This Post
        Picture of CommonwealthSparky
        posted Hide Post
        Reinventing the wheel methinks. Never can remember when a second subfloor needed to be installed in a certain way. Might be a regional thing though.


        Popeye only reached for the Spinach can as a last resort...
         
        Posts: 1453 | Location: Central Pennsylvania | Registered: Jun 02, 2010Reply With QuoteReport This Post
        Picture of Jaybee
        posted Hide Post
        A second layer of subfloor is rare, but is used in the case of making a stiffer floor (to offset tile or a diagonal finished floor) or if floor framing is further apart (common when using engineered trusses). In most cases, properly installed 3/4" T&G subfloor panels will be enough subfloor structure to support a variety of finish flooring materials.

        As for what direction to install a second subfloor layer, I stand by my original answer. A 3/4" subfloor will provide enough support for any additional layers added on top - no matter which way they are installed. So span length is effectively zero. Unless you use a non-subfloor rated 3-ply plywood, you are not going to see any measurable difference in deflection over the 8' or 4' dimensions with a multi-ply product. OSB subflooring of course has no structural orientation differences.


        Jaybee
         
        Posts: 10363 | Location: Knoxville, Tennessee | Registered: Sep 27, 2003Reply With QuoteReport This Post
        Picture of CommonwealthSparky
        posted Hide Post
        All we ever used the 15 years was the product Advantech.


        Popeye only reached for the Spinach can as a last resort...
         
        Posts: 1453 | Location: Central Pennsylvania | Registered: Jun 02, 2010Reply With QuoteReport This Post
        Picture of Jaybee
        posted Hide Post
        Agreed. Once we found Advantec we never went back. I had always used T&G plywood for subfloors as OSB products were the cause of us getting a lot of work. Even so, it became standard procedure to install the plywood and then immediately coat it with some water seal - just to ward off any rainstorms that could happen prior to dry in.

        When OSB gets wet, it swells. When plywood gets wet, it can delaminate. Advantec can take several wettings with no issues.


        Jaybee
         
        Posts: 10363 | Location: Knoxville, Tennessee | Registered: Sep 27, 2003Reply With QuoteReport This Post
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