Back4.1.6.2.(4)

ATTRIBUTION:

Most technical provisions of the BC Fire Code describe how the code’s objectives and functional statements are achieved. However, some provisions, like this one, do not relate directly to a code objective. The following analysis is provided to assist in understanding of the provision.

 

APPLICATION:

Wind exposure factor for calculating the specified snow load on areas of roofs and other building surfaces of buildings in the Low and Normal Importance Categories subject to snow accumulation, where:
  • the building is in an exposed location, which means the roof is exposed on all sides to wind over open terrain [i.e. level terrain with only scattered buildings, trees or other obstructions, open water or shorelines] and is expected to remain so during its life,
  • the area of roof under consideration is exposed to the wind on all sides with no significant obstructions on the roof, such as parapet walls, within a distance of at least 10 times the difference between the height of the obstruction and CbCwSs/γ metres, where γ is the unit weight of snow on roofs, and
  • the loading does not involve the accumulation of snow due to drifting from adjacent surfaces.
This applies to buildings described in Sentence 1.3.3.2.(1) of Division A and to buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9] that are required to be designed in accordance with the requirements of Part 4.

INTENT:

To supersede the application of Sentence 4.1.6.2.(3) and allow a reduction of the wind exposure factor where site wind conditions reduce the maximum expected accumulation of snow on roofs or other building surfaces subject to snow accumulation from that corresponding to a wind exposure factor of 1.0.