Direction of wood vs joist direction
 

OK, I'm putting in a wood floor (3/4" pre finished Birch) in my dinning room, I have heard its best to install the wood in the opposite direction of the joists under the floor. However we have two other rooms where the wood it going in the same direction of the joists, and after 20 years, never had a problem. My wife and I are arguing over this. I feel if we run in opposite direction, it won;t look right, (I think the boards should go in the direction of the longest part of the room.) Does it really matter how to lay it as long as we have the proper sub floors down? thanks

A proper subfloor takes the joists out of the arguement. I would argue for all hardwood in the same direction in the house and for a single room, run it in the longest direction.

The 3/4 should be opposite from joists for hard wood floor same direction as the 3/4 ply, if you add 2nd layer of ply you would want that layer the same as the joists.

http://www.hardwoodinstaller.com/hardwoodinstaller/floor-layout.htm
The fact that the old floor installation was successful would indicate a substantial subfloor.

Not sure I understand Isola's comment so for the record here is what I have under the floor.
currently have carpet, subfloor consists of 3/4 chip board (USB I think its called,) on top of that I have 5/8" particle board, the particle board is coming out and being replaced with 5/8" plywood, My wife who is hammering me on this, sent me the exact link that NealTw sent which supports her arguement to run the wood opposite as the joists. If I get what you guys are saying, as long as I get the sub down right, it should not matter the direction of thwe wood, ???if I have to run the way she wants it, it will look like hell.

I thought you would find where it said "some will work" and yours already did. If your adding 5/8 plywood over 3/4 sub you will be good for which ever direction you settle on. I beleive the sub is called Adventech and they do call for 3/8 ply overlay to run the floor in same direction as joists.


For years most construction has been using common 5/8 or 3/4" sub flooring over joist systems. In some cases thinner material may have been used. None of these are suitable for a problem free floor installation running parallel to the joists. Sure in some cases it may work, but others not.

From joists up 1st ply perpendicular from joists,
2nd layer is opposet from the 1st bringing second layer of ply the Sam direction of the joist.

Just triing to figure this out. If we assume plywood is bend resistent in both directions, which I am not sure of: what would it matter? If we assume it it better in the length and your triing to take the movement out of the floor, wouldn't you want to add the strenght in the same direction. I would think you want to make sure the joints don't line up with joints below and all end joints land over a joist.
I went looking and couldn't find anyone saying to turn it. They do say to glue it down.:cool:

I have had many issues discussing the fact that weather the 2nd layer of ply should go same as the 1st, now I was taught this way, I just stick to what I know. The reason to put the 2nd layer opposite is to counter sync the seams of the 1st over leaping them by like 2ft, your fist layer of ply already exceeds the wait limit by the span theory
So you are taking the weakness out of the joints by doing it this way has nothing to do with the joists for the second layer. I do this when I tile so I do this in any other room that floor needs to be replaced. I also don't tile on cement board I use my 2 layers and never had a tile crack yet so I'm not about to change it now.