Attic Floor -- Plywood question

[Wharf Rat]

Just put some pull down stairs in yesterday so that I can actually use the bigger of the 2 attics for storage.

Now it's time to go get some plywood to make a floor. I've never done this before and there are like 7 million types and thicknesses. I never knew there were so many choices.

Anyone know what I size/type should be buying to do this?

 

[Road Head]

Just put some pull down stairs in yesterday so that I can actually use the bigger of the 2 attics for storage.

Now it's time to go get some plywood to make a floor. I've never done this before and there are like 7 million types and thicknesses. I never knew there were so many choices.

Anyone know what I size/type should be buying to do this?

Will you ever be putting any finished flooring up there? Or will this be plywood attic floor for all time? What are the dimensions that you will be covering? What spacing are your joists? Typical is 16", but if your roof is trussed, you might be farther apart.

I really like 3/4" plywood as a solid surface.

 

[Ralph]

19/32 t&g sturdi-floor.

 

[RhodeIslandRed]

Is it just for storage? 7/16 OSB.

 

[RhodeIslandRed]

But the Wazny manual would say 3/4 t&g plywood. Marine grade.

 

[BirdOPrey5]

Forget plywood, just use Sheetrock.

 

[RhodeIslandRed]

1/4 diamond plate steel. Painted with Duraliner.

 

[synonymous]

But the Wazny manual would say 3/4 t&g plywood. Marine grade.

Modern plywood seems more poorly made than the stuff of yore. They don't fill the voids between the plys like they should, and the material is of lesser quality over all. I had a chunk of 3/4" from circa 1995 I used in my remodel here, and it was WAYYYYYY more rigid and of better quality than the modern stuff.

 

[Wharf Rat]

Will you ever be putting any finished flooring up there? Or will this be plywood attic floor for all time? What are the dimensions that you will be covering? What spacing are your joists? Typical is 16", but if your roof is trussed, you might be farther apart.

I really like 3/4" plywood as a solid surface.

It will never be finished, only storage. Plywood floor forever.

Have not measured the spacing yet. Will try to do so tonight.

 

[Wharf Rat]

19/32 t&g sturdi-floor.

Is it just for storage? 7/16 OSB.

But the Wazny manual would say 3/4 t&g plywood. Marine grade.

Forget plywood, just use Sheetrock.

1/4 diamond plate steel. Painted with Duraliner.

Six response, five different answers. Thanks guys

Yes I know BOP was kidding and RIR was kidding with the steel. But seriously I figured this would be a pretty standard answer and a lot less of a choice.

Modern plywood seems more poorly made than the stuff of yore. They don't fill the voids between the plys like they should, and the material is of lesser quality over all. I had a chunk of 3/4" from circa 1995 I used in my remodel here, and it was WAYYYYYY more rigid and of better quality than the modern stuff.

And here comes Wazny the senior citizen garbling on about the old days and how they don't build em like they used to without even giving me a recommendation.

 

[BirdOPrey5]

My 'real' opinion is also 3/4".

 

[synonymous]

And here comes Wazny the senior citizen garbling on about the old days and how they don't build em like they used to without even giving me a recommendation.

3/4" T&G is what should be used for all sub flooring. They make some 1" stuff, but that is way overkill, and fawking heavy.

Oh yeah, even if you get the stuff from the SAME FAWKING RUN, don't expect the T&G dimensions to be consistent.

 

[Road Head]

It will never be finished, only storage. Plywood floor forever.

Have not measured the spacing yet. Will try to do so tonight.

There arent as many choices as you think.

Basically, you will want something between 1/2" thick and 3/4" thick. Tongue and groove is nice, but not necessary unless you think you may want to lay some type of flooring over it in the future (hardwood, tile, etc). Sounds like you dont, so I wouldnt worry about it.

The closer together your joists are, the thinner plywood you can use. If your joists are on 16" centers, 1/2" ply would probably be fine, but be aware that it could have a little sag when you walk across it. 3/4" isnt much more expensive, and would give you a sturdier surface.

Be sure that when you lay the plywood, the grain is perpendicular to the joists. I would also screw it down, just get some 2" deck screws.

 

[synonymous]

There arent as many choices as you think.

Basically, you will want something between 1/2" thick and 3/4" thick. Tongue and groove is nice, but not necessary unless you think you may want to lay some type of flooring over it in the future (hardwood, tile, etc). Sounds like you dont, so I wouldnt worry about it.

The closer together your joists are, the thinner plywood you can use. If your joists are on 16" centers, 1/2" ply would probably be fine, but be aware that it could have a little sag when you walk across it. 3/4" isnt much more expensive, and would give you a sturdier surface.

Be sure that when you lay the plywood, the grain is perpendicular to the joists. I would also screw it down, just get some 2" deck screws.

expoxy coated ring shank nails out of nail gun FTMFW. Screwing that down would suck.

 

[Wharf Rat]

There arent as many choices as you think.

Basically, you will want something between 1/2" thick and 3/4" thick. Tongue and groove is nice, but not necessary unless you think you may want to lay some type of flooring over it in the future (hardwood, tile, etc). Sounds like you dont, so I wouldnt worry about it.

The closer together your joists are, the thinner plywood you can use. If your joists are on 16" centers, 1/2" ply would probably be fine, but be aware that it could have a little sag when you walk across it. 3/4" isnt much more expensive, and would give you a sturdier surface.

Be sure that when you lay the plywood, the grain is perpendicular to the joists. I would also screw it down, just get some 2" deck screws.

There's the answer I was looking for.

3/4" it is.

Thanks Scooter.

expoxy coated ring shank nails out of nail gun FTMFW. Screwing that down would suck.

Makita FTW. It'll take like 2 seconds.








Next Question

The insulation sticks out above the joists, so I can't just lay the plywood there. Obviously I am going to have to cut and nail down some sort of lumber on top of the joists to elevate the floor a little. Only needs a couple inches.

What should I be using here, simple 2X4's? 4X4's if I find I need the height to clear the insulation??

I was going to lay them literally on top of the joists going in the same direction and either screw or nail them down, not going perpendicular to them. I assume that's the correct way?

 

[synonymous]

rip 2x2 furring strips and liquid nails them to the truss/rafter.

 

[synonymous]

A bead of liquid nails will go a long way towards the strength of the whole mess as well. Lay it as though you were laying any other floor.

Make it look like this.

 

[Wharf Rat]

Cool, will do. Thanks.

How come liquid nails for the furring strips? I think I read somehwere to nail or screw it down....

 

[synonymous]

Cool, will do. Thanks.

How come liquid nails for the furring strips? I think I read somehwere to nail or screw it down....

Just use a few nails/screws. Let the adhesive do the real bonding work. Stuff has come a long way. The wood will break before the bond of the adhesive does once cured.

 

[Road Head]

Cool, will do. Thanks.

How come liquid nails for the furring strips? I think I read somehwere to nail or screw it down....

More strength, especially laterally. Glue is also really useful for helping cut down on squeaks, although, in your application, squeaks probably dont matter. But in the main part of the house, it can really help solidify the subfloor and help keep the wood from rubbing together and making noise.