When framing a roof, first calculate the needed measurements of roof framing rafters. To find out the span of roof framing, measure the width of the building. Divide that number by two to get the run, which is the horizontal distance between the two rafters. After that, use an online roofing calculator to find out the rafter lengths. Before obtaining lumber, determine how long it needs to be by referring to the horizontal run of the rafter.
Once you have the lumber, find a straight, long and light piece to create a pattern. Mark where you have to cut it to make it the needed length, put it on a saw horse, and cut the piece at the proper angle. Mark the outside edge of the building on the rafter using a framing square for accuracy. Cut a birdsmouth on the lumber piece to ensure that the rafter reaches the outside wall of the building. To create the birdsmouth, slide the framing square on the rafter up to the mark you made earlier.
There are seven types of rafters that professionals use in roof framing; it is possible to create any roof using these seven types. The most popular roof framing rafters include common, hip and hip jack rafters.