One of the most time consuming tasks in homebuilding can be the cutting of a roof. In some cases it can take as long to cut and frame the roof as it does to frame the rest of the house. It can also require a lot of space to get the job done. It is in ones best interests to plan ahead during the course of construction to be ready when it comes time to cut the roof.
Whether the roof be a simple gable roof or a complex roof with multiple hips and valleys you want to be able to cut more than one rafter at a time. Sawhorses become a valuable commodity during the roof cutting phase of construction. Cutting a half dozen or more rafters is what you want to try for. To achieve this there are a few options available to the roof cutter.
If you only have one set of horses, nail an eight foot 2x4 flatwise to the top of them. This will allow you to mark and cut six or more rafters depending on their width.
The second option is to use two pair of sawhorses. Just like the previous option, nail a 2x4 flatwise over the top of two horses. In this instance you are not limited to an eight foot 2x4. You can use an 8, 10, 12, or even a 16' 2x4 depending on how much room you have to work in.
The third option is to make your own sawhorses out of a 2x10. Put legs on it just like a normal sawhorse. Again, your only limitation is what you have available for length of 2x10 and how much room you have to work.
Another time saver is to make a rafter pattern. To do this, pick the straightest piece if lumber you can find from the rafter material. Once you have determined the length of your rafter from the plumb cut to the birdsmouth, the depth of the birdsmouth, and the length of the rafter tail, transfer this information to the material. After you have marked all of this on the 2x, carefully and accurately cut the rafter. This is going to be your pattern for the rest of the rafters so you want to be precise with your cuts.
The next move is to nail stops to the top of the pattern. Cut two pieces of plywood about 6" long by 2 1/2" wide. Nail one to the top of the 2x about 2" from the plumb cut, letting it hang over both edges of the 2x one half inch. Nail the other piece just above the birdsmouth. You now have a pattern to mark the rest of your rafters without having to measure each and every one of them.
When you are ready to start cutting the rafters, lay as many boards on the horse as you can and have enough room for the saw to fit inbetween each one. When laying the boards on the horses, have all the crowns pointing in the same direction (When looking down a board while flat most boards are bowed one way or the other. The convex side would be the crown). Take the pattern and lay it on top of each board with the plywood stops resting on the crowned edge and mark them.
You are now ready to cut rafters. When making your cuts, cut the pencil line. Cut the plumb cut first and then move to the birdsmouth and tail. Depending on how many rafters you are cutting you may have to slide them back and forth so you are not reaching over to far to make your cuts with the saw. When cutting the birdsmouth it is okay to over cut it to totally remove the material.
Homebuilding and cutting rafters can be a dangerous job. Always exercise caution and safety when framing or using a skilsaw.