Roof Overhang Wind Pressure

Acting on the bottom surface of the overhang in combination with pressures acting on the top surface.

Roof overhang wind pressure.

Qz 0 00256 kz kzt kd v2 lb ft 2 or. Overhangs on the leeward and side edges shall have the basic zone pressure applied. Effective wind area 26ft 2ft or 26ft 26 3 ft 52 ft 2 or 225 33 sq ft. Where zone e or g falls on a roof overhang on the windward side of the building use eoh and goh f or the pressure on the horizontal projection of the overhang.

Kz is velocity pressure exposure coefficient. The velocity pressure is depending on wind speed and topographic location of a structure as per the code standard velocity pressure q z equivalent at height z shall be calculated as. Wall 41 2 psf roof 11 7 psf. The effective wind area should be the maximum of.

This procedure addresses roof overhangs via footnote 8 on figure 28 6 1. For the leeward overhang the coefficient for the leeward wall c p 0 5. 0 10 20 and 30 and the highest negative area weighted pressure coefficient was found to be 0 540 for 10 roof slope with 0 wind incidence angle on face a. Qz 0 613 kz kzt kd v2 n m 2.

Effective wind area 225 33 sq ft. Wall 27 5 psf roof 6 5 psf end zone. Obstructed wind flow is considered when 50 or more of the area below the surface of the roof is composed of objects inhibiting wind flow such as a canopy atop a concrete basin at a wastewater treatment plant. Windward parapet 0 0 psf gcpn 1 5 windward roof leeward parapet 0 0 psf gcpn 1 0 overhangs 20 6 psf upward add to windward roof pressure horizontal mwfrs simple diaphragm pressures psf transverse direction normal to l interior zone.

Since trusses are spaced at 26ft hence this will be the length of purlins. In order for a structure to be sound and secure the foundation roof and walls must be strong and wind resistant. Purlins c c roof pressure from 30 4 2b the effective wind pressures for zones 1 2 and 3 can be determined. Overhangs roof truss tails zone 2 p 20 1 2 2 44 2 psf use trib area of tail zone 3 p 20 1 2 5 50 3 psf roof deck at overhangs zone 2 p 20 1 2 2 44 2 psf zone 3 p 20 1 3 7 74 4 psf.

Canopies with less than 50 obstructions below the roof surface would be considered clear.