Per asce 7 the mean roof height h is defined as the average of the roof eave height and the height to the highest point on the roof surface except that for roof angles of less than or equal to 10 the mean roof height is permitted to be taken as the roof eave height.
Mean roof height.
45 is a standard value for the slope α for the thickness of the roof r 30 cm are assumed.
The picture below shows the pitch of a 7 12 roof slope meaning that for 12 of horizontal measurement roof run the vertical measurement roof rise is 7.
Height z only used for part 3 h 60 windward pressures and positive internal pressures for partially enclosed buildings k h velocity pressure exposure coefficient evaluated at the mean roof height h used for low rise roof leeward and simplified pressures and can be used for all cases.
Calculates height length and width of a gable roof from the angle of slope and the thickness of the roof.
The height h means height above base not height above ground.
Examples of asce 7 16 roof wind pressure zones for flat gable and hip roofs.
Printed with permission from asce.
So why is mean roof height even important and why is it even listed on the plans.
As a reminder please don t forget to add height of rafter thickness of roofing material and ridge vent to the number that you ll get using our calculator.
This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.
The mean roof height would be the average of 12 plus 22 67 or 17 33 as shown on the building plans.
The coefficients for hip roofs are based on the h b ratio mean roof height to the building width ratio and for roofs with slopes from 27 to 45 the coefficients are a function of the slope.
Calculate the height of your roofing surface using the width and pitch.
For example if your roof is 20 feet wide and has a pitch of 1 2 which means it rises 6 inches in height for every 1 foot of width the height of your roofing surface from base to peak is 10 feet.
At a base width b of 500 cm the height is 292 43 cm.
So why is mean roof height even important and why is it even listed on the plans.
If your goal is to only calculate the roof height do not enter any numbers in wall height field and only use building width and roof pitch fields.
