What Are the Standard Dimensions Between Roof Joists?

List all of your dimensions. You need the length and width of all spaces to be spanned by the roof. You also need to list what pitch you want for your roof. You can express pitch in two ways. For example, you can ask for a 30-degree pitch. You can also express this as 7/12. This indicates you want the roof to rise seven inches vertically for every 12 inches of horizontal run. If you only know the degree of pitch you want, that will be fine.

Go to your local lumberyard. Salespeople at lumber yards sell pre-built truss systems, and they will help you order the right trusses for your project. Give the salesperson the dimensions of the spaces you want to put the roof over. This figure is called the “span.” Also give the salesperson the pitch you want for the roof. This information goes into a computer that has special software specifically designed for ordering pre-built trusses.

Choose the type of load you want your roof to bear. You need to decide what kind of weight will be on top of your roof. In regions with heavy snowfall, you must be prepared for heavier loads. This will determine how far apart the rafters should be. The most common distances are 24 inches and 16 inches. The 16 inch distance will hold a heavier load.

Choose the size of lumber you want. You can choose between 2-by-4 lumber and 2-by-6 lumber for pre-built trusses. The wider lumber will support a heavier load, especially if you ask for 16 inches between roof joists.

Order your trusses. Once your salesperson has entered all of your specifications, the computer will print out a roof design. You can order the trusses on the spot, and expect them to be delivered in two to three weeks