My house is over a 100 years old & single level. There is no sub floor. There is only one thickness of flooring. Even though the floor in the crawl space is insulated, this floor is cold. It has a 3" wide T&G red fir, straight grained floor & it's been sanded numerous times. The joints are not tight anymore either. I presume it was once 3/4", but after all the sanding that this floor has seen, who knows how thick it actually is now. So I'm looking to put some new T&G oak over the top of the old fir, and just use the old fir as a sub-floor. The old floor was laid across (perpendicular) the floor joists. So, which direction do I lay the new oak floor? It makes sense to run the new floor in the opposite direction of the existing fir floor. But that would have the new floor running parallel with the joists. Not every piece of the new floor would be nailed into the joists this way. I know the joists are the main thing, but the old floor is pretty stable, in spite of it's appearance.

I'm planning on screwing the old floor into the joists, so it is solid & tight, with no squeaks. So, it makes sense to me to lay the new floor across (or perpendicular) to the existing fir floor. Will it be a stronger floor if the new floor is laid perpendicular to the existing floor instead of running the same direction as the old floor? Does this make sense?

I also didn't want to lay down any plywood substraight between the two floors due to a thickness issue meeting up with another floor in an adjoining room.

I've laid T&G floors before, but only in new construction that used OSB or plywood sub-floors, which are very stable. We always went perpendicular to the joists in these situations. So this is a new challenge for me.

Any and all comments and suggestions are welcomed. Thank you.
Starlight.

Star, if you don't add a plywood subfloor over it consider going 45 degrees, along with the joist is never good.

Johannes.

I like the 45 degree idea. Was actually considering that option. That would probably add a little to the amount of materials used. Does anyone know if there's a formula percentage wise, how much more you add to a job when you go off a 45 degree, to the joists?

Add about 12-15 % to the sq.footage.

Johannes.

And you should charge yourself another 25% for a 45.

LOL, I like that. The charge or price I put on my self in my own home is priceless. So now that we've established that laying this floor at 45º angle is the way to go. Where do I start? Do I start in the middle of the room? That will be sort of difficult going back the other direction with a floor nailer. Part of the room has a bay window, and the angles on the bay are at 45º angle to the joists & sub-floor planks (or close enough for who it's for). Maybe I need to start off of one of the bay's angles? Whatta ya think?

Start somewhere in the middle of the main area and lay out all your working lines. You need to screw down a "starter board" first along the line where you start to have a starting base to nail up against. Once you have installed a few rows you remove the starter board and immediately glue/slip a slip-tonque (also called a "spline") in the groove and nail this row immediately to prevent shifting away from what you nailed in already. Now you can nail from the other direction as you install boards again. Next immediately nail in a few more rows along the side with the spline to assure that that side will not shift on you.

Than you can continue working to whichever side you want.


When you move into other rooms laying wood you will need to string working lines and screw down again a "starter board" and repeat the same as when you started in the middle with the "starter board" (and spline reversing nailing direction) to assure you maintain a straight line.

Johannes.