(1) Except as provided in Sentences (2) and (3), the accumulation factor, Ca, for areas adjacent to roof-mounted vertical projections shall be calculated in accordance with Sentence 4.1.6.5. (1) using the following values for the peak accumulation factor, Ca0, and the drift length, xd:
(a) Ca0 shall be taken as the lesser of,
0.67 · (γ h / (C_b S_s)) and (γ l_o / (7.5 C_b S_e)) + 1
(b) xd shall be taken as the lesser of,
(i) 3.35h, and
(ii) (2/3)l0,
where,
h =height of the projection, and
l0 =longest horizontal dimension of the projection.
(2) Ca is permitted to be calculated in accordance with Article 4.1.6.5. for larger projections.
(3) Where the longest horizontal dimension of the roof projection, l0, is less than 3 m, the drift surcharge adjacent to the projection need not be considered.