This past weekend I finally got around to putting an attic ladder in
my house. The attic floor is 2X6's 16"OC. It has some tongue and
groove flooring in part of the attic, but I wanted to add more
flooring. What is typically used for flooring, just regular plywood or
"Typically" would depend on what you plan to use the attic for.
In my crawlspace attic, which is just for storage, I used 1/2" ply,
since all I ever do is crawl around up there to move boxes around. If
I was going to be walking around, I'd probably go with something
Also keep in mind that you have to get it up into the attic. That may
be why part of the floor is T&G. Individual strips of wood are easy to
fit through the opening. I couldn't get full sheets of plywood up into
my attic via the pulldown ladder, so I cut it into 24" x 16" wide
strips so it would fit atop the joists.
One last issue: the insulation.
If the insulation is going to fit under the floor, in the 2 x 6
spaces, then you don't (or won't) have enough insulation to do much
good. You don't want to pack the insulation down since that will cause
it to lose some R-value.
I'd add the sleepers to hold the storage floor at right angles to the
existing joists, with blocking to provide a box section so the floor
doesn't collapse when you crawl over it. My attic only has a rather
inconvenient scuttle hole in hallway for access, and living alone in a
1400' house with a basement, I didn't really need the storage. So I just
insulated over the strip of floor that was near the scuttle hole.
Reframing a big hole to add stairs was more pain than I cared to
undergo. My attic gets rather hot, so not much could safely be stored up
there anyway. Don't forget to build an insulated box with an insulated
lid to go over the stairs, or it will act like a chimney leaking all
your warm or cooled air go right up into the attic.
And go to harbor freight and buy a cheap set of knee pads and a pair of
gloves, and keep them at the top of the stairs. Along with a pack of
disposable dust masks, if you are sensitive to insulation dust. Don't
know about you, but I can't crawl on wood floors any more, and splinters
from rafters and floorboards (not to mention errant fiberglass shards)
are a PITA I can do without.
I would go to 5/8 , especially if the rafters are 24"OC. One word of
caution-- do not nail it down. Use screws. Nailing to the rafters is a
good way to damage the ceiling, knock light fixtures loose, etc. Larry
16" OC, attic, limited storage, I would use 3/4" OSB (non- T&G) since I am
a big boy. I would let the guys at the BORG rip it down to 2x8 sheets for
That should mate flush with the T&G you already have.
Honestly 1/2" 16" OC would be fine for most people.
4x8 T&G OSB or plywood is what is used in a normal situation.
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I did this project a couple years ago. I agonized over what sheathing
material to use as is my custom. :)
I had 2x4 (full dimensional lumber) and fiber glass roll
insulation. I added another nearly full dimensional member to
preserve my insulation space by gluing (epoxy) onto the upper face.
The span were short like 10' or so becuause of the ceiling / roof
I dont know your local heating / cooling environment but you might
consider adding a 2x4's (cheap hem-fir) to the upper face of the
2x6's to give save your insulation space and use some thin plywood
gussets to hold them in place.
Alternatively you could install them at 90 degrees to the 2x6's &
toenail....more of PITA to insulate but the construction would be way
Foam boards have about 2x the R value per inch, if you're tight on
head room, you could go with foam.
Anyway....sorry for the "off question" reply
about sheathing thickness....
I fianlly settled on 15/32 OSB which is APA rated at 32/16; 32"
rafters for roof or 16" joists for floors.
I'm 205 & my buddy who helped me is closer to 250. Would I use 15/32
for a "real" floor? No way! I'd use 3/4" plywood.
But for an attic floor that I walk on maybe once a week....less than
$10 a sheet is hard to argue with.
I was concerned 15/32 would be too thin but it has worked out just
I screwed it down with Hardi-backer square drive screws (12" o/c) so
in case I need to remove it I could.
Its a nice tight floor...btw I installed it smooth side up so its
really easy to slide boxes around.
On Tue, 19 Jan 2010 11:08:18 -0800 (PST), Mikepier
It took them years, but the people here finally convinced me that
since I had trusses** holding up the roof (on 24" centers), the bottom
part wasn't really meant to hold a floor, that I would walk around on.
Nonetheless, like Derbydad, I had already put in something like a
floor. I used 3/8" plywood. iirc. It bends a bit when I walk on it,
but I try to step right above a truss.
I have only a hole in the closet ceiling, so I cut the 4x8s into 4'x
16" pieces. Another reason why I didn't use 1/2 inch.
**Each is a triangle, pointing up, with an upside down W inside the
triangle. The center has quite a bit of space, plus I had to crawl
out to other areas to put in phone lines, ceiling fixtures, co-axial
cable for the tv, burglar alarm sirens and wires to the swithhes.
Plus electicity to power the roof fan and the light. And now to
power the floodlight on the side of the house.
We had a folding stairs in the house I lived in during JHS and HS, and
I think there there were no trusses and the partial floor was 1x6's,
but plywood wasn't so common then I think. It was a suburban ranch but
built maybe 1950. But the roof was shallower and there was less area
to stand in, even when I wasn't fully grown.
If you already have tongue and groove, your attic is probably nicer
than either of mine.
It took me 20 years to floor my attic. I hauled it up there mostly one
piece of plywood at a time adding on as I needed more storage. Most of
the stuff I took up there 20 years ago is still there, hasnt been
touched since it was first put up.
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