Roof Style & Pitch
Two key aspects of your home’s roof that you need to become familiar with are its style and pitch. These two things will determine a great deal about your new roofing system.
There are several types of structures and styles of roofs, especially in homes and residential construction. The types and complexities of trim and accessories will be somewhat dependent upon the type of roof you’re working with.
A roof consisting of two flat roof surfaces which intersect at the ridge over the entire length of the building. This is the most basic of the double slope roofs.
A roof which consists of one flat roof surface sloped to one side of the structure. This is a single slope roof.
A roof with the ends inclined, as well as the sides.
A roof which consists of more than one roof surface, where one plane intersects another at someplace other than the ridge.
A roof with two sides, each of which has a shallower slope above a steeper one.
When considering a new roof, the pitch of your specific roof must be taken into consideration.
The pitch is typically expressed as a fraction. For example, a pitch of 4/12 would represent 4 inches of rise to every 12 inches of run.
There are two methods to calculate the pitch of a roof.
Determine the entire width of the building, including any overhang which may exist. (It may be helpful to drop a plumb line for measurement.) Divide that width by 2. Next, measure the height of the gable at the roof’s ridge. Divide this number by 1/2 the width to determine the pitch. This is the number that will be placed over 12 in the fraction.
Hold a level horizontally at the eave parallel to your rafter run. Measure 12 inches from the end of the eave, and measure a line vertically to the roof line. This number will be the top number in the roof pitch, placed over 12 in the fraction.