We have an 800SF L-shaped floor area on which we are planning to install 3/4" T&G prefinished hardwood. We would like to run the plank direction all the same way throughout the area, but have some concerns as this will result in the planks running in the same direction as the floor joists in part of the area.

It's new construction, the main floor over a full basement, with 5/8" plywood subfloor, glued, nailed and screwed onto the 16" o.c. floor joists.

In the sketch below the direction of the subfloor joists are marked in blue, and the staircase is shown:



We would like to run the hardwood planks from left to right on the sketch.

1. Is it acceptable to run the hardwood planks in the same direction as the floor joists over part of the floor?

Any comments or suggestions on our dilemma would be greatly appreciated!

An additional layer of at least ½" plywood will let you go any direction you wish.

Have you thought of doing the floor at an angle?

Not good. You will either need to add an additional layer of sq.edge plywood underlayment, lay the floor on a diagonal, or go underneath and block between every joist with a 2x4 or 2x6 24" OC.

Thanks to all for your reply.

I am considering running the boards at an angle - but not sure if we would be happy with an unconventional approach.

Jerry, I noted that you specified square edge plywood for an additional layer - why not T&G - is this to allow for expansion? Any other recommendations for the second layer - assume it should be run perpendicular to the base layer, and should it be glued?

Angles look sweet. I have seen wood run on a 22.5 - 30º angle, and it really "wowwed" ya. Very different, and with the contemporary funishings in the home, it was the bee's knees.

Floorguy, maybe installing on an angle is not such a bad idea. You certainly make it sound nice. We will have a corner fireplace in the top right corner - perhaps I could start off the hearth - this would be a 45 angle though, maybe not as impressive as a more shallow angle.

Can you point me to any photos on the site showing an angled installation?

Because the existing walls are in the way getting it down and you don't need a T&G anyway when there is already a subfloor supporting it, no joist clear spanning to deal with.

Here is a "sorta" pictorial of a diagonal installation I did last year. I think diagonals are a nice change for people to seriously consider.
http://www.custom-surfaces.com/31.html

I put my floor down on a 45 angle. Everyone who has been over has said how different it is and how much they like it. And of course the most important thing, my wife and I really like how the diagonal looks.

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Jerry, the diagonal floor in your pictoral looks outstanding.

If there is no border, then I assume you would measure and cut each piece as you meet the wall at the correct angle, leaving approx. 3/4" expansion gap. With the boards on an angle I'm thinking you may be able to get the nailer closer to the wall, but probably still need to facenail the last nail?

In terms of a DIY project, would you say that a diagonal installation is any more or less difficult?

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It is easier to get under doorjambs!!

There is more labor involved and also the waste factor, about 15% to 18% if you have a decent wood. Door jambs slow me down more on a diagonal, with a door jamb in place some cuts are almost impossible on a wider width plank floor. I have to stop two rows short and cut and dry fit boards many times. Every row you will be using the floor nailer and a finish nailer on both ends. It's going to take you a while longer and use a little more material. Normal labor rates run a little higher for a diagonal.

Apples to apples it is cheaper using a diagonal layout than it would be for adding a plywood underlayment for running a parallel layout.

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An update on this thread - I have discussed the issue with our home builder and he insists that no additional plywood layer or under-reinforcement of the subfloor is needed because the area is in fact supported by joists 12" o.c. (not 16" as I had incorrectly assumed).

Would you agree and should I concede to his judgement and run the hardwood planks parallel to the 12" o.c. joists?

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I'm thinking The problem is the 5/8" deal, not so much the OC spacing.

Well I thought about it. If I (me) were asked to do this job I would add a minimum 3/8 BC underlayment because it is still only 5/8 thick which is already at the bare minimum for holding fasteners securely. I am more anal when its my butt on the line.