If your roof rafter connectors will not be visible after your construction project is completed, it may be possible to connect these rafters together using a rafter splicing technique. You will want to check your local building codes before undertaking this type of construction, as there are very specific ways that roof rafters can and cannot be spliced together. If done correctly, however, this can be a legitimate way to connect rafters to one another.
Step 1 - Measure Rafter and Ridge Cuts
Use a bevel square to measure the cuts in the ridge board where the rafters will be placed. It is important to make sure that the cuts are equal distances from one another and are all the same width and depth.
Step 2 - Cut Rafters
Line the rafters up on rafter horses and cut them to length. Again, it is important to make sure that all of your rafters are cut to the same length. Use a circular saw, measuring tape and a pencil to make sure that all rafters are cut to equivalent lengths.
Step 3 - Notch Rafters
Cut a bird's mouth notch in each rafter on the end that will rest on the lip of the exterior walls of your structure. Do this carefully in order to ensure a snug and secure fit. You should be able to use your circular saw to make these cuts. As always, be careful when using your circular saw to avoid injury to yourself and damage to your rafters.
Step 4 - Begin Aligning Rafters
Beginning at one end of your structure, begin aligning rafters from opposite sloping sides of your roof so that they meet at the ridge of your house. Once you have 2 rafters aligned so that they meet in the middle, attach them to the place with 16-penny nails.
Step 5 - Splice Rafters Together
Once the rafters are placed against one another over a load-bearing beam or wall, you will be able to splice the beams together for structural integrity. To do this, you will use gusset plates on either side of the rafters. Use pieces of lumber that are the same width as the rafter beams themselves and align them on either side of the rafter beams. Using 16-penny nails, secure the gusset plates to either side of the rafter beams. As an alternative to nailing these gusset plates to the rafters, you may also be able to find pre-manufactured metal splicing plates that are specifically designed to be used for this purpose. If you have to splice more than one set of rafters, just make sure to stagger them on separate load-bearing beams or walls.
Step 6 - Structural Integrity
Rafter splicing is typically used as a last resort for erecting rafters and is not generally the preferred method of constructing roofs. A ridge board is a much better way to secure rafters to your roof, and will almost always be a better way to go.