Need flooring advice FAST

[Bassman]

I'm putting down some plywood over the existing 1x6 subfloor in my kitchen. Should I be trying to put all the long edges along the joists? Does it matter? We'll be installing sheet flooring over it. The room is 8x13 with the "alley" being down the center of the 13" length and about 4 feet wide so my first instinct was to hide as many joints as possible under the counters. Tomorrow's the day, any advice is welcome.

 

[Rdtompki]

Plywood is normally mounted in the other direction since it is stiffer in the "long" direction. You should get an answer from a pro soon who might have some further advice as far as how to attach to the subfloor. If your first layer were plywood you would normall not attach the second layer to the joists. Don't know about a plank subfloor, however.

Rick

 

[Sponsor]

 

[Gary Swart]

The best thing to use is 1/4"x48"x48 Multi-ply. This is intended for underlaying vinyl flooring. It has no voids in the inside plys. I was told this is to prevent a woman wearing high heels from breaking through by stepping on a weak spot. It isn't much more expensive than regular 4x8 plywood. It is grid marked where screws should be sunk in. You screw it down heavily then fill and sand the seams. I may have various names, but if you verify there are no voids, you'll be OK. The 4x4 sheets are much easier to handle than full sized sheets, too.

 

[Jadnashua]

The plywood actually ends up working better if you don't attach it to joists when it is a second layer...it only needs to be attached to the planks. It does need to have the grain crossing the joists for maximum strength, but when the stuff is only say 1/4" thick, it doesn't add much anyways. It's more of a factor when installing tile. Before you install the ply, make sure to screw down any loose planks. It wouldn't hurt to hit all of them with screws, but that's your call. You don't want the stuff flexing and squeaking.

 

[Bassman]

The plywood actually ends up working better if you don't attach it to joists when it is a second layer...it only needs to be attached to the planks. It does need to have the grain crossing the joists for maximum strength, but when the stuff is only say 1/4" thick, it doesn't add much anyways. It's more of a factor when installing tile. Before you install the ply, make sure to screw down any loose planks. It wouldn't hurt to hit all of them with screws, but that's your call. You don't want the stuff flexing and squeaking.

Thanks. I already bought some plywood (1/2") so I don't think I'm going to be looking for anything more specialized than that. I spent quite a bit of time today screwing down the planking do I'm confident that it won't be moving around. If I don't have to worry about lining the ply up with the joists that'll make life easier. Another question: on another forum I was warned not to use glue. Any reason why not? Thanks again for the help.
Neil

 

[Jimbo]

. Another question: on another forum I was warned not to use glue. Any reason why not? Thanks again for the help.
Neil

If this is the correct procedure, the reason might be because planks and plywood have different rates...and direction..of expansion and contraction.

 

[Jadnashua]

Dimmensional lumber moves too much with seasonal changes and would break the bond, so gluing planks to plywood won't work long-term.

All of the subflooring methods do not suggest gluing the layers together (do not confuse this with gluing subflooring to the joists). The reason for this is that doing it incorrectly is worse than not doing it at all; primarily because you can introduce voids which is death to a tile install. But, if you glue plywood layers together, two layers of the same type glued properly with full coverage and then clamped (screwed) properly verses just fastened together with screws or nails is 8x stiffer than the single layer alone.

FWIW, for maximum strength and to minimize deflection from the second layer, the ends should be 1/4 span offset from the previous layer. Since the previous layer started centered on a joist, and if you have say 16" joists on center, the end of the second layer of plywood should be ideally 4" from the joist. When laying ply together, also avoid having four corners match up...offset the ends.