in the IRC Tables such as R802.5.1(2) there is a reduction of rafter spans based on the height of the rafter ties above the plate. i.e. A 2x12 spf at 24" o/c can span 21'-0"
and if the rafter ties are at mid height factored by 0.58 = 12.18'. My calculations show this to rafter to be overstressed. Has anyone else found this to be true?![[shadessad]](/data/assets/smilies/shadessad.gif "[shadessad] [shadessad]")
or B-(
and at 2/3 the overstress is even worse.
In addition table (1)(ceiling not attached) has a span of 18' and table (2)(ceilig atached) has 21' and it seems to me that the spans in table (2) should be less than table (1)
In regards to rafter ties not collar ties the dissertation in paragraph 802.3.1 appears to allow these ties at 48" o/c but that makes the overstress in the above cases even worse.
Has anyone had this come up?
and if the rafter ties are at mid height factored by 0.58 = 12.18'. My calculations show this to rafter to be overstressed. Has anyone else found this to be true?
or B-(and at 2/3 the overstress is even worse.
In addition table (1)(ceiling not attached) has a span of 18' and table (2)(ceilig atached) has 21' and it seems to me that the spans in table (2) should be less than table (1)
In regards to rafter ties not collar ties the dissertation in paragraph 802.3.1 appears to allow these ties at 48" o/c but that makes the overstress in the above cases even worse.
Has anyone had this come up?
