Is it okay to go with 3/4 inch OSB for the flooring up there. It doesn't need to hold anything too heavy (except my big ass when I'm up there). Primarily boxes of stuff the wife won't let me throw out. Would 1/2 inch OSB be too thin? OSB okay, or do I need to go with plywood?

1/2 would probably be ok, but its going to flex when 'your big ass' stands on it and your not over a joist. 3/4 would be a better bet i think.

1/2" OSB is standard for attic flooring and cheaper than 3/4"

I used 1/2. If your rafter spacing is less than 30 inches or so, it will be plenty. I supported mine with a 2x4 center crossbeam when I did mine for a little extra security because my garage had over 36" spacing...

also, these days, so long as it doesn't get extended exposure to water, OSB is generally considered as good as ply for most applications.

1/2 inch OSB sounds like the consensus. Thanks for the help.

1/2" osb or cdx plywood would not meet building codes for walkways and platforms for attics. I doubt an inspector would ever say anything but if you have the chance, put in 3/4. I have seen some inspectors allow 2 layers of 1/2". Another option would be to get 2x12's and put them up there. They may be easier to get up an attic access or scuttle hole easier than 4x8 sheets of plywood.

You can get 3/4" plywood for around $16 a sheet right now ans 1/2" OSB is around $6.

No way 1/2" osb spans 30"! If you weigh anything over 50 pounds you'll be flyin' through your sheetrock ceiling as soon as you step on that!

Joists are typically spaced at 12" to 16" on center. 3/4" will suffice for about 40psf and that is plenty for pretty hefty storage spaces. Cut them into 2' wide strips and run the perpindicular to the joists.

[This message has been edited by Salty Aggie 93 (edited 2/4/2009 10:37p).]

i was using 1/2" osb in my attic space right before i put my leg through the garage ceiling, i couldn't walk for a couple of days, be careful that you step on the joists until you are finished.

I built a cedar closest in our attic for my mom back in highschool. That why she could put all of her clothes up there. While you are building it might be something to think about.

Edit:sorry can't spell

[This message has been edited by RBoutdoors (edited 2/5/2009 8:24a).]

clothes?

i would go with 3/4". I have some of both in my attic as I used what I had. Unless you are just really wanting to save a little money. It will support more and you won't have to worry about walking around on it. I can walk around any of the 3/4" with no problem. But the 1/2", I have to stay over top the beams to feel real safe.

Another vote for 3/4. This will be project #1 when we move into our new house at the end of the month.

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If you've got the space how hard would it be to finish out part of an attic, complete w/ HVAC vents, to serve as a man-cave?

Not for a media room, but as a place to keep my hunting & fishing stuff and set up a rod-building/fly-tying bench.

How are you getting 4 X 8 plywood up in the attic? It does not fit up the ladder.

Ah, you folks must be talking about an attached or incorporated garage. I have a detached garage, and used 1/2 inch (13mm) ply on the 30" spaced josts, and it held me up there with a bunch of stuff as well. Granted, I bought quality wood with almost no voids and 5 plies, and backed it with a 2x4 down the center of each board between joists.



[This message has been edited by MouthBQ98 (edited 2/5/2009 4:43p).]

And quality makes a big difference. You can walk across 3/8 inch ply with a 30" spacing between base supports IF that ply is BS1088 7 ply marine grade...

That stuff is voidless, seamless, and VERY tough....and expensive.

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How do I get a 4X8 into the attic?

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Rip the 4X8 into two 2X8 (minus kerf) and shove them in the attic. If you have gaps more than 24 inches, run them lengthwise.

quote:

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...man cave...HVAC...

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It is entirely possible, but if your house has blow-in insulation, you are going to have some work on your hands. The first step will be to insulate your rafters, which may be cost-preventitive.

You may also run into some problems with the roof vents via the soffett and air flow to the ridge vent. If you are going to A/C the area, you will need to seal both off in order to prevent serious efficiency loss.

Then, you may want to upgrade your attic stairs to an aluminum one in order to accomidate the increased traffic. Widening it wouldn't be a bad idea either, in order to fit bigger stuff up there.

The best idea would be to build an isolated insulated ventilated man room as a portion of your attic. Kind of like a closet or backyard tool shed in your house that is difficult to access and functions not unlike a treehouse. "No Girls Allowed" sign is optional.

(you can tell I've given this some thought...)


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If you can read this, thank a teacher.
If you can read this in English, thank a Soldier.

Thanks for the info Opie. We've got a 1.5 story house with a ton of attic space and 2 access points upstairs w/ full sized doors and a drop-door in the garage.

What I'd do is seal up the current drop door, move the entrance point from the garage and install separate stairs going up from the garage. It might even be better to wall off an insulate a room there and then install a small window unit-style AC solely for that room rather than try to run new ducts & vents.

I do think the "no girls allowed" sign would be required.

Okay, so the 3/4" seems the way to go now. But sounds like OSB is still fine...which saves me from the cost of the plywood. Thanks for all the responses.