Does it matter?

September 10, 2009 8:08 PM

Should hardwood floors always be installed perpendicular to the joists?
posted by blue_beetle to Home & Garden (11 answers total)

Best answer: I'd think if I was installing them over a subfloor (if you're not installing them over a subfloor, then yes, it's absolutely mandatory that your floor span between the joists) I'd actually rather have the flooring running parallel to the joists. The subfloor, whether plywood or whatever, would run with its longer direction perpendicular to the joists and then you'd lay your wood floor perpendicular to the subfloor so that you minimize areas where you've got one wood strip entirely nailed to one section of subfloor. But even that might not matter.

I'm curious as to where you've seen that the floors should be perpendicular?
posted by LionIndex at 8:18 PM on September 10, 2009

Best answer: Generally hardwood flooring should be laid at at least a 45 degree angle to plank sub flooring. With sheet sub flooring orientation is less critical but laying perpendicular to joists will stiffen the feel of the floor especially if it's only marginally stiff to begin with.

However sheet subflooring is the norm in current houses and floors are required by code to meet minimum deflection ratings (though as with all things code they are bare minimums and can be improved) so strip flooring in modern houses is mostly laid to enhance the look of the room.
posted by Mitheral at 8:41 PM on September 10, 2009

Exactly what Mitheral says. Running with the joists= weaker floor. Running against the joists= stronger floor. 90 degrees "against" the joists being the strongest.
posted by Taurid at 10:10 PM on September 10, 2009

If you _really_ want to run parallel with the joists, you can put blocking between them (boards of the same size as the joist that cross-brace for stiffness). This is common when installing a decorative board pattern on a deck, for example.

Of course, this can become a huge project involving rerouting utilities when done inside.
posted by bfranklin at 5:37 AM on September 11, 2009

Hmmm... I'm not sure why it really matters. Assuming you have sheet sub flooring over your joists, I can't justify why your choice of finish material would make a difference to the integrity/strength of the floor. By laying carpet you aren't adding a material that would produce a "stronger" floor, so I'm not sure why you couldn't lay the wood any way you wanted.
posted by comatose at 6:18 AM on September 11, 2009

My house is pretty well built (it survived a direct hit from a 60 ft. maple with minimal damage) and has hardwood floors in a few rooms that run in both directions. The floors are installed over sheet subflooring.
posted by TedW at 7:12 AM on September 11, 2009

Best answer: The classic plank subfloor would run at 45 degrees to the joists. As stated above, with the modern use of plywood subflooring, this is no longer done. Then, running the hardwood perpendicular to the joists under the subflooring is the best way to get your minimum deflections.

Some rooms may look wrong with the flooring running one way rather than another. I bet that this is what you are dealing with. Then, as bfranklin suggests, you will have to beef up the joists to avoid problems.
posted by Midnight Skulker at 7:12 AM on September 11, 2009

To clarify a little, the flooring is installed parallel to the long axis of the rooms (presumably for aesthetics) regardless of the way the joists run.
posted by TedW at 7:14 AM on September 11, 2009

Best answer: I didn't think it mattered which way the boards ran, provided there was an adequate subfloor, but I looked it up anyway and found this pretty good article about it.
posted by orme at 7:44 AM on September 11, 2009

Response by poster: Thanks for the advice guys, that sounds about what I expected.

FYI: I asked because I've read a few articles that say they should always be perpendicular without an explanation.
posted by blue_beetle at 9:13 AM on September 11, 2009

Don't think it matters. Do what looks best; the direction of the planks will affect the appearance of the room.
posted by kenliu at 7:19 PM on September 11, 2009