A roof joist is the part of the home that holds the load bearing of the roof itself. These roof joists are positioned from one wall to another and has to be strong enough to handle the weight of the roof system. Installing roof joists must be done before the actual rafters are placed on the building. While the thought of installing the roof joists may seem daunting to the do it yourself homeowner, it is a simple process.
Step 1 - Measure Top Wall Plate
In order to get the right amount of 2 by 6 lumber to use as your roof joists you will need to measure the top wall plate. The roof joists will need to be spaced at 16 inches on center. This means that from the center of one joist to the center of another there is 16 inches.
Step 2 - Install Joist Bracket
There are basically 2 different ways to attach a roof joist to the top wall plate. The joist can be toe-nailed into the top plate, or a joist bracket can be used. The bracket is a better idea for the fact that is prevents any type of warping, or rollover, of the joist when it is under heavy load. Since the joist sits on top of the wall plate, the metal brackets are important for keeping the joists sturdy. Set the bracket on top of the top wall plate and nail them into the wood.
Step 3 - Lift Roof Joist Into Position
When the joist bracket is installed on top of the wall, the roof joist can be set into position. Make sure that the adjacent bracket is lined up with the first so that the joist is in a straight line. You will also want to make sure that the joist is positioned with full bearing on the wall. This means that it takes up the entire width of the top plate. For a standard 2 by 4 wall, the bearing must be at least 3 1/2 inches. Set the 2 by 6 lumber into the bracket and secure with 16d nails. There will be one nail on the top and one on the bottom.
Step 4 - Continue Installing Roof Joists
With the first joist into position, you can then continue lifting the other joists into place and securing them into position. Make sure that you have picked over the lumber good enough so that there isn't any type of bowing, sagging or bends in the joists.
Step 5 - Install Cross Ties
In homes that have a wide span across the joists, or there is a large roofing system that is going to be built, there should be some thought as to installing cross ties on the joists. These cross ties are 2 by 4 lumber that is installed in between the joists to keep them stable, and straight, under heavy load. Measure the distance between the hoists, and cut off 2 by 4 pieces. Toe-nail these pieces to each of the joists. Depending on the weight, you may use three to four in between each joist.