You need a subfloor of some type.

I"ve never heard of any one nailing the wood floor strips directly to the floor joists. Normally, they aren't thick enough to handle the load. How far apart are the joists?

Run your floor the long way on a subfloor and use a reducer.

If you are running the hardwood parallel to the joists, you need to add a 3/4 inch plywood layer for support with reducers down to lower height floors. Otherwise, you have to run it perpendicular to the joists.

It will look fine running crossways. I ran into this putting hardwood in my hallway. I actually had to run it horizontally across the 4 foot hallway. It looks totally fine.

Sorry, I wasn't clear when I reread my post...I mean a 3/4 inch plywood in addition to the subfloor if you want to run it parallel to the joists.

I know I'm a tile guy, and I don't know much about hardwood. But one thing I DO know is that subfloor or not, it should run perpendicular to the joists.

If you run the flooring parallel to the joists you run the risk of a wavy floor and/or increased squeaking when you walk across it. The best choice is perpendicular to the joists.

Yes, we did in our kitchen area, in order to run the flooring perpendicular to the joists in the rest of the larger room. The contractor nailed wood supports below the floor between the joists to support it. Luckily the basement was below and unfinished so it was easy to do.

Once upon a time someone got the bright idea to run subfloor planks diagonally; that way the homeowner could run the finish floor in whatever direction they preferred, and the support would be the same.
FF to now, when we use plywood or OSB subfloor, and the choice is still up to the homeowner; if you have 3/4" subfloor, feel free to run finished flooring whichever way agrees with the look you're after.
Casey

Oh no, I didn't mean literally taking out the subfloor to put them directly on the joists! I thought a subfloor was absolutely critical to a house, which is why I didn't mention ours.

So yes we have a subfloor, ours is OSB - 3/4" PS-2-92 rated (meaning it supports 3/4" hardwood). Our joists are the standard 16" apart - and we have an over 5' crawl space to easily access them.

I know the cracking and sagging are the risks with running parallel - but everything I've read says it takes several years to get that point. The 2 solutions I've came across are:

1. putting in 3/4" plywood over the subfloor: no go for us because it will make my kitchen floor sit much higher than the surrounding floors - dangerous to say the least, even with a sloped transition piece (not to mention highly unattractive).

2. putting in support between the joists, right against the subfloor. I have found several hardwood authorities online listing this as a viable option.

I was wondering if anyone here has just installed it parallel anyway. Sometimes I know that's done.

OR

If anyone has done modification #2 and their experience with that.

We took out our kitchen flooring yesterday - linoleum and it's 3/4" sawdust board underlay. Now it's bare subfloor.I don't think it's the weight that's the problem (it supported the sawdust board just fine), I think it's the system (planks) that could lead to cracks (separation of planks). Adding support between the joists should technically support it, and 5 or 6 hardwood places online mentioned it as a solution.

I had the same issue. I chose to run the boards diagonally and love it. We did this in both the living room and the bedroom. However, the hall boards are parallel to the joists (hall is typical 3 feet wide). The floor has been down for at least 15 years and it is fine.

We have a subfloor that has the boards running diagonally (built in 1952). We took out the old hardwoods that ran one direction and put in new ones that run the opposite direction. Didn't change the subfloor or add extra support as far as I know.

Dannie, that's good news about your hall. I would think if it doesn't do it there, it wouldn't do it in the other rooms if you ran it parallel.

I tend to think that Casey might be right - 3/4" OSB such as we have should be strong enough on it's own. Adding in extra support on the joists here and there is very minimal work and would just act as an extra precaution.

As an update to my post above, my husband informed me our hardwood floors PREVIOUSLY ran parallel to the joists...for 60 years with no problems. Again, we do have the diagonal subfloor boards though...not sure if that makes a difference.

Yes, we did modification #2, adding supports between the joists up against the subfloor. The joists in our kitchen, dining area and family room run in two different directions so we had to run the wood flooring perpendicular to the joists in the dining and family rooms, but parallel to the joists in the kitchen. So far with the supports underneath there has been no problems with the flooring. No cracking or sagging. We used 5" red oak plank flooring. Good luck!

Marcy, yay, someone who did it! That's great that it's working out.

Was it a lot of work? We would be doing it ourselves.