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Unblaanced snow on 12 in 12 roof

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I was just looking at an existing roof the the owner would like to add some new load to. The slope is 12 in 12, in an uninsulated attic space, 25psf ground snow load. By my reading in ASCE 7-05, the entire roof effectively has to be designed for Ixpg=25psf, whereas in the past (ASCE7-02) the load would be 1.5ps = 1.5*(0.7*I...*pg)*Cs or 1.5*(0.7*1*...*25)*0.6 = 15.75 psf.

Is there some errata I've missed? This is nearly a 60% load increase from the previous code. I realize that it only affects steeper roofs (8 in 12 to 32 in 12), but it seems like there's a gap in the code application.

By the way - does anyone actually check to see if ridge board roofs work for unbalanced snow loads, or do we all just close our eyes and hope that a couple .131 toenails and friction keep the roof from collapsing? Experience dictates the latter - both on paper and in the field.

--

Jordan


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