Sec 2.62 defines the mean roof height as the average of the roof eave height and the height to the highest point on the roof surface, except that, for roof angles less than or equal to 10 deg, the mean roof height is permitted to be taken as the roof eave height. To do this we first need our mean roof height (h) and roof angle.

This will give us the most conservative C&C wind pressure for each zone.Д¬hapter 30 of ASCE 7-16 provides the calculation methods for C&C, but which of the seven (7) parts in this section do we follow? We just have to follow the criteria for each part to determine which part(s) our example will meet. Most of the figures for C&C start at 10 sq ft and so for the purpose of this example we will consider an effective area of 10 sq ft for all wall and roof wind zones. When calculating C&C pressure, the SMALLER the effective area the HIGHER the wind pressure. (Note: MecaWind makes this adjustment automatically, you just enter the Width and Length and it will check the 1/3 rule) In this case the 1/3 rule would come into play and we would use 10ft for the width. Width = The effective width of the component which need not be less than 1/3 of the span length.ДЄs an example, a roof joist that spans 30 ft and are spaced 5 ft apart would have a length of 30 ft and the width would be the greater of 5 ft or 30 ft / 3 = 10 ft. To determine the area we need the Width and Length: In order to calculate the wind pressures for each zone, we need to know the effective area of the C&C.

Asce 7-10 chapter 30