Residential attic live load 1

[Bammer25]

Hopefully this is easy for some of you. I’m PE but 99 percent of my work is in steel and concrete (nuclear/industrial). Anyway, I’m helping my contractor out. He has a double true hoist spanning under a load bearing wall that the inspector wants a letter for. The double true joist is not adequate when considering dead plus a live load of 40 psf.

The space the wall supports is an unfinished attic with joists spaced two feet, so nobody is going to be walking up there and I highly doubt they will even put plywood down.

My question is does the code allow us to neglect live load here? Going off memory the LL for unfinished attic is 40 psf which will kill it.

 

[JAE]

We've used 10 psf for unfinished (non-occupied) attic live loads.
However, we don't combine that LL with any roof snow (non-concurrent)

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[MIStructE_IRE]

In Ireland/UK an unoccupied attic imposed storage load is 0.25kN/m sq to cover the christmas tree and suitcases!

If the attic has been converted we’d use 1.5kN/m sq.

 

[Bammer25]

Ok thanks. I’m not worried about anything failing, but I don’t want my reputation at stake if I’m not following code. I don’t know how much these inspectors dig.

 

[JAE]

This is from ASCE 7-05 (7-10 the same):

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[Bammer25]

Good deal. That may get it. I didn’t look at asce 7, just IRC.

 

[MIStructE_IRE]

Interesting that the US storage load is almost 4 times the Irish equivalent!

 

[jdgengineer]

The live load for attics that are not habitable range from 10psf - 20psf. The code requires that you design it for 20 psf if the space in the attic is large enough to fit a certain size box. The idea is that if there is space for a box someone will eventually put one up there.

The 10 psf load does not need to be combined with roof live load. The 20 psf does. See the footnotes to the table in ASCE 7 that JAE posted for the limitations as to when you need to consider the higher storage load.

 

[Ron247]

It will be 10 or 20 psf. See the footnotes to determine if yours is considered "with storage" or not.