Installing parallel or perpendicular to the joists

Q: I plan to install solid maple hardwood flooring over the existing 5/8″ tongue and groove plywood subfloor. Do I need to install additional plywood subflooring if the hardwood flooring is going to be installed parallel to the floor joists, instead of perpendicular to the joists?

Is the existing 5/8″ plywood subfloor (screwed to the joists) adequate to hold the nails/staples? Thanks for any info you can share with me.

A: 3/4 flooring should be installed across the joists. If for some reason (room layout) this is undesirable, I would screw another 3/4 layer over top. What you have with 5/8 is not near adequate or stable enough to support you floor and everything else you will put on it.

As an alternate, you could install the floor diagonally. It is more cutting waste and more time consuming to do. But it will save you the cost of additional plywood and could make for an interesting layout.

Similar Q: I want to install a 3/4 pre-finished floor over a existing a 33/4 pine t&g which is perpendicular to floor joists. Sub floor is 3/4 on the diagonal. The existing pine floor goes the length of the room and I would like to run the new floor in the same direction. The new floor would be perpendicular to the floor joists, but running the same way as the existing pine floor. Is that okay?

A: The prefinished floor will be sitting on a base which is likely 1 1/2″ thick. You can install the floor any way you wish. Installing it lengthwise only makes sense.

Related Q: My house is about 8 years old. My hardwood floor is running the same direction as my floor joists. Will this cause problems in the future?

A: It could open up at some points, depending on whether the structure moves. 3/4 thick floors are suppose to be installed across the joists.

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