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I have a 3 car garage and want to see what your all thought about my ability to store Christmas lights and random other boxes up there.

The setup is: two 2x12s (placed next to each other) on 24 inch spacing that span about 20ft over the 2 car garage portion. over the 1 car garage portion are single 2x8s on 24 inch spacing and that is 10ft spanning. there is a huge beam and support pillar between the 1 car garage portion and the 2 car garage portion.

I have put some 3/4 plywood down over the joists for storage and moved about 15 boxes of christmas stuff up there. Thoughts on how much weight it can hold?

Also, maybe related to storage or related to foundation work we had done but I've noticed some nails popping out of the sheetrock on one beam. House is about 7 years old.

during building

second photo while building

attic now

attic now 2

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  • Is the single car section about ten foot span? 2x8s and 2x12s are quite big for an attic floor joists/trusses. As long as light stuff is not packed wall to wall/floor to ceiling(roof), it should be okay.
    – crip659
    Commented Jan 24 at 14:12
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    Yes 2x8s span about 10ft, sorry I updated the post,
    – user903805
    Commented Jan 24 at 14:17
  • A few pictures of what you've got would sure be helpful.
    – JACK
    Commented Jan 24 at 14:22
  • " store Christmas lights and random other boxes" It sounds like you are the heaviest thing up there and if you haven't fallen through, you're good to go. Commented Jan 24 at 15:55
  • I go alittle overboard on Christmas lights… I have 16 rubber made bins…. I just added some photos from when the house was being built
    – user903805
    Commented Jan 24 at 16:43

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That area appears to have been designed under the IRC's "habitable attics and attics served with fixed stairs." See IRC R301.5. The joists are sized to carry 30 psf live load and at least 10 psf dead load (20 psf dead load for #2 grade or better, non-Southern Pine joists).

The doubled up 2x12s on 24" centers are equivalent to single 2x12 joists spaced on 12" centers (equivalent for the purpose of sizing joists, not for selecting floor sheathing thickness). Under the 12" joist spacing rows of IRC R502.3.1's Table R502.3.1(1), all of the #2 grade species have maximum joist spans longer than 20'-0" (for 10 psf dead load, where excluding Southern Pine they pass for 20 psf dead load). Under the 24" joist spacing rows of the same table, the single 2x8s are confirmed as 30 psf live load for all #2 grade species (again under 10 psf dead load, where excluding Southern Pine they pass for 20 psf dead load).

That carrier beam at one end for all of the joists looks like an LVL. Checking its consistency with the "habitable attics and attics served with fixed stairs" IRC category is unfortunately outside the IRC's scope, but it would have been a foolish waste to not size it for the 30 psf live load.

Unless somebody snatched defeat from the jaws of victory with an undersized LVL carrier beam, that loft area is probably designed for 30 psf live load.

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  • Thank you for the extensive information. Is there a way to test and see if it is southern pine? This house is in Houston Tx, which is southern… but not sure if it’s that simple? Also, does 30 psf live load correspond to roughly 30 pounds per foot of storage weight or is that more dead load? Also also, it is strange to be rated so high without actual stairs, I had to add my own ladder to the attic, but it is a national builder house and I didn’t select the $5000 ladder and attic decking package but maybe they built it to accommodate that option so they didn’t have to have 2 attic design plans
    – user903805
    Commented Jan 24 at 19:29
  • @user903805, I usually go to the Home Depot website, set my locale to the place (Houston in this case), and type in 2x8 to see what species pop up. 2x8 yields Southern Pine. 2x12 yields Southern Pine. If you look at enough of your joists, then maybe you can find a grade and species mark, e.g. thisoldhouse.com/woodworking/21015464/…. 2x12 Southern Pine on your layout is 3.8 psf. 1/2" drywall is about 1.6 psf. 23/32" OSB is about 2.5 psf. The 10 psf dead load capacity is sufficient. The 30 psf live load is equivalent to a sleeping room in the house.
    – popham
    Commented Jan 24 at 19:45
  • @user903805, I worry a little that the framing may be partly intended for supporting the roof. That piece bearing on the joists looks like it could be using the joists as transfer beams or something. Consistency with the 30 psf floor joist table is jarring, though, where I expect that it's a 30 psf area up there. I would want to putz around some to assert definitively. Assuming that it is, however, if you would be comfortable with the weight on a bedroom floor, then you should be comfortable with the weight up there. Just be sure to get the strength axis on your 23/32" sheathing correct.
    – popham
    Commented Jan 24 at 19:50
  • I added 2 more photos I randomly had in my phone from up in the attic is now if that helps with seeing the roof rafter tie into the center support beam. But main take away, 20 boxes of Christmas stuff and a few other random items maybe ok?
    – user903805
    Commented Jan 24 at 20:51
  • @user903805, interesting. I think those are the ridge supports that I was anticipating. Still can't say for sure. For your actual question, though, you're definitely okay with the Christmas stuff. Anywhere there is 42" between the roof rafters and the tops of the joists, the IRC requires a 20 psf live load capacity, so you're fine.
    – popham
    Commented Jan 24 at 21:00

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