Standard Roof Truss Angles

Roof pitch and corresponding angles.

Standard roof truss angles.

Common or standard trusses are symmetrical and have standard four inch heels. The most commonly used roof pitches fall in a range between 4 12 and 9 12. Usually average roof pitch is determined using the same roof length method. It s often used for sheds garages or extension of an existing roof.

A mono truss is a one sloped truss that forms a right angle triangle. The truss is a framework consisting of rafters posts and struts which supports your roof. A mono truss roof allows for more sunlight and visual space proper drainage and relatively cheaper. 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.

If the overhang exceeds 2 5 feet we will need to use a larger top chord for the overhang typically a 2 6 top chord for the truss. This is useful because sometime you may need to cut a bevel with your circular saw that is not calibrated using roof pitch style this setting on circular saws is calibrated in degrees. A standard overhang is 16 24 inches but the overhang can be any length you wish. Angle the angle of a roof is the same as the roof s slope except instead of being represented as x 12 it is represented in degrees.

Pitches above 9 12 are very highly angled and are designated steep slope roofs. As we will see below there are several different types of designs and this will impact the angles and designs of the overall truss. Pitches lower than 4 12 have a slight angle and they are defined as low slope roofs. This forms an angle of 18 5 between the horizontal section and the roof and creates a gentle incline that is seen as a midpoint between a low pitch and medium pitch roof.

This means if a roof rises 4 in the length of 12 your roof pitch would be 4 12 or 18 43 degrees. Greek says one must keep rafter length in range of 1 9 to 1 7 th of span but as per roman style the standard dimensions are kept about 1 3 to 2 9 th of span with an angle of 23 to 24 degree. Pitches of less than 2 12 are considered flat roofs even though they may be very slightly angled. Commonly it is 3 4 th of span as per gothic rafter must be equal to span.

On blue prints architects engineers usually display the pitch of a roof in the format shown on the image where number 4 represents a rise and number 12 represents a length. This measurement is best done on a bare roof because curled up roofing shingles will impair your measurement.