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I recently discovered that I have an unfinished attic in a guest bedroom on the second floor of my house, above the garage. The overall area is behind the closet in the bedroom and is approximately 10x20' wide. It has 2x6 joists spaced 16" on center.

I was hoping to put some 2x4s across the joists and add some plywood across to make a floor and use this space for storage. However, I don't know how much weight I could safely store up there. There is even a electrical switch and bulb in the area suggesting that may have been intended to function as a storage space?

Would an attic like this support mild to moderate storage weight if a floor was added? Are there any safety issues or other general concerns I should have? Any advice would be much appreciated

Here are the pictures of the attic: Unfinished Attic Space - 10'x20'

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  • I hate to ask, but what's that dryer duct doing there? Is it supposed to be connected to something?
    – Aloysius Defenestrate
    Apr 16 '20 at 15:35
  • There is a bathroom on the other side of the wall. I am assuming that is the vent for the bathroom fan. I thought it was strange too but I am not sure if that is common or just lazy work. I always thought the bathroom vents were suppose to be routed outside?
    – agentbanks217
    Apr 16 '20 at 16:00
  • Bath fans are absolutely supposed to be vented outside. If you dump warm moist air into a cold space, you'll get condensation which leads to mold.
    – Aloysius Defenestrate
    Apr 16 '20 at 21:12
  • Well I guess I'll have to add that to my to do list to figure out how to that at some point.
    – agentbanks217
    Apr 17 '20 at 23:40
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I just ran an analysis and you can store 20 psf safely on this, which is the code requirement for storage above ceilings. This is with the weight of the 2x4s you wish to add.

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  • Thanks for the quick reply! Would that mean I can store approximately 4000 pounds (20 psf x 200 sqft)? Also, is there a calculator or similar reference I can use to arrive at that 20 psf figure you provided?
    – agentbanks217
    Apr 15 '20 at 21:43
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    Yes, but make sure you evenly distribute that 4,000 pounds over the full area. Don't place a heavy piece of equipment, like a workout machine or a box of weights, right in the middle and assume it's fine because it's less than 4,000 pounds. Spread the weight out over all the joists as much as you can.
    – represton
    Apr 15 '20 at 21:48
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    How is this area going to be accessed? If going from the garage, any door that you put in that wall must be fire rated. I did that exact thing and the inspector required that I use a 2 hour fire rated door, which nobody sells for small access hatches. So I had to buy a full sized solid fire rated door and cut it down. Not a big deal, but an important one.
    – JRaef
    Apr 15 '20 at 22:46
  • No it can only be accessed from the guest bedroom. The access is located in the closet and was covered by a frame with some drywall and was attached with screws. I think I may make the opening bigger and make a new 'door' for it. But that is dependent on how much weight it can safely support.
    – agentbanks217
    Apr 15 '20 at 22:54
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    FWIW, represton's answer is on point with all comments. And I'll reiterate, 20 psf is code minimum, that is how they arrived at it, then checked to make sure that the joists are ok for it. And again note: 20 psf = 20 psf, don't try some logic leaps to get around that. There is a difference between designing for area loads and point loads, it may be trivial at times and other times it isn't. Do you know the difference when it is and when it isn't important? If you don't, stick to 20 psf
    – Ack
    Apr 15 '20 at 23:12

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