Handbook Question

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    Thomas LaPerriere

    You only use half the span because the load is split between the ridge beam and the bearing wall equally.  You apply the loading to the 5' to either side of the ridge beam for the total load on the beam.  The loading for the other half of each span is carried by the wall, which is a separate calculation.

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    Yong Jae Kim

    oh I see. The bearing walls were counted. thank you!

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    Artem Melikyan (Edited )

    Just curious about 2 questions:

    1. I had assumed that the attic ventilation requirement in IBC was to prevent ice damming, but the rationale in the handbook says it's to prevent moisture. Was my assumption totally unreasonable? If you ventilate under the roof sheathing it prevents melting of snow above and thus ice damming. 

    This is what the code says and the question below:

     

    2. The handbook rationale says the image (below) was taken from AGS. Was anyone able to find it?

    I looked twice and did not.

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    Gang Chen (Edited )

    The attic ventilation requirements in IBC has always been to prevent moisture and condensation in the space, even in areas with no snow, the ventilation is required.

    The language you quoted above states that you should protect the opening from snow and rain from entering into the attic space, no mention of melting snow.

    Gang Chen, Author, Architect, LEED AP BD+C (GreenExamEducation.com)

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    Artem Melikyan (Edited )

    Understood,

    So this code requirement is not supposed to also help the "ice-damming" condition (see below)?

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    Gang Chen

    Correct, the attic ventilation is to outside, so the attic temperature is the same as the outside air. No impact on melting snow.

    Gang Chen, Author, Architect, LEED AP BD+C (GreenExamEducation.com)

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    Gang Chen

    IBC section 718 regarding draftstopping and fire blocking for concealed spaces is also important:

    https://codes.iccsafe.org/content/IBC2015/chapter-7-fire-and-smoke-protection-features#IBC2015_Ch07_Sec718

    Sprinklers may also be needed specifically in the concealed spaces:

    https://www.woodworks.org/experttip/are-sprinklers-required-in-concealed-spaces-such-as-floor-and-roof-cavities-in-multi-family-wood-frame-buildings/

    Gang Chen, Author, Architect, LEED AP BD+C (GreenExamEducation.com)

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