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Can I use 2x4's as flooring joist for storage in attic?

Can I use 2x4's as flooring joist for storage in attic?

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Old 05-05-19, 05:48 AM
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Can I use 2x4's as flooring joist for storage in attic?

I have trusses 24" OC spanning 30' across my addition and would like to make a little storage space in my attic, I plan on running a joist from one truss brace to the other which is almost 12'. Will a 2x4 span that far and hold the weight of 4x8 7/16 OSB boards or should I use 2x6's ?
 
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  #2  
Old 05-05-19, 06:05 AM
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You said you want to support 7/16" OSB. Are you building this just to support one sheet of OSB or do you plan to store other things up there? If so, how much weight will you be storing?

The "right" answer is that you can not modify, alter or use engineered trusses for storage. They are designed to carry the loads they are designed for and nothing else. You need to contact your truss manufacturer and let them run the engineering on your idea to see if the trusses can safely support the weight you want to store.

Once we know what (weight) you want to store in the attic we can offer more advice.
 
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Old 05-05-19, 06:05 AM
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It's not the weight of the OSB but the weight of what is stored that is the concern. Attic trusses aren't designed for that type of load. While a 2x6 would stiffen it some it doesn't do a lot if there is no support from below.
 
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Old 05-05-19, 07:37 AM
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You need to contact your truss manufacturer and let them run the engineering on your idea to see if the trusses can safely support the weight you want to store.
That's right. And for all we know they might approve your plan... or they might not.
 
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Old 05-05-19, 07:03 PM
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I'm going to use the storage just for light boxes, holiday lights, clothes boxes, odds and ends, nothing heavy like furniture or anything. I have a wall running under the center of the trusses which they rest on, also the trusses I have are free span if that helps with anything. I'm not going the full length of the attic, only about 10 ft which I would only need 4 pieces of OSB for the flooring.
 
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Old 05-05-19, 07:49 PM
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The question is not only about weight... it is whether or not a horizontal member will somehow disrupt the equilibrium on the truss joints. Your truss members alternate between tension and compression, which are always supposed to perfectly offset each other. Contacting the mfg is standard procedure anytime a modification is made to a truss.
 
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Old 05-05-19, 08:58 PM
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Trusses are an engineered system designed to hold up a roof. Maybe your truss system can hold some weight on the bottom chord but only the manufacturer can tell you that.
 
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Old 05-06-19, 02:58 PM
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Trusses are not made to carry an internal load.
 
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Old 05-06-19, 04:49 PM
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Ok, I wasn't sure if I could use a little of that extra space in the attic or not, now I know. Thought I'd ask before I started something I wasn't sure of, thanks for all the info...
 
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Old 05-06-19, 04:53 PM
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You still don't know because you still haven't asked the truss mfg!
 
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