Scissor trusses are a specific type of roof truss, that is created when there is a difference in the pitch of the roof planes and a vaulted ceiling. Specifically, a roof truss is a triangular shape, formed from lumber pieces, that can be adjusted to specific shapes and dimensions in terms of both the roof and the ceiling. In most cases, truss members need to be joined together with specialized metal plates, designed to anchor and support the roof structure. Forming a scissor truss can be accomplished by using a basic construction technique that compresses a triangle-shaped from lumber so that it more closely resembles the blades of a pair of scissors.
Step 1 -- Plan Truss Design
It is recommended to consult with a reputable architect when formulating a plan for your scissor truss design. This is important, in terms of both correct dimensions, and of how appealing the end result will look. An architect can examine the overall plan for a room's finished design, and incorporate the appearance of your scissor truss. If necessary, also invest in the help of a construction contractor, to be sure you have the exact measurements of all lumber pieces, so that your scissor truss will be secure and stable.
Step 2 -- Arrange Workspace
Once you have the plans and dimensions for your planned scissor truss, you will need to construct it in an area large enough for the finished product. This is usually outdoors. Also, make sure you have enough room to cut all of the lumber pieces and organize them according to how they will be fastened together.
Step 3 -- Cut and Build the First Truss
Your first truss is the most important because it will determine the structural integrity of the finished product. Construct this prior to cutting any additional lumber pieces. Be sure to follow the exact measurements, and remember that it is easier to cut a piece slightly too large because it can always be trimmed down.
Once you have cut all the pieces for your first truss, fit them together according to your design. Fasten each joint together, using the needed number of nails through the metal plate. Your completed truss measurements should match those in your blueprint; if they do not, make any necessary adjustments before proceeding.
Step 4 -- Cut Remaining Pieces
Once you have determined that all measurements match up for the first phase of your scissor truss project, it is time to cut out the rest of the lumber, according to the design plan. Make a note of any adjustments that you may have needed to make when building the first truss, and use these to ensure that the remaining pieces fit together accurately. Arrange and fasten your lumber pieces. Check again that all measurements match to those on the blueprint, and fasten them together using the same technique as in step 3. When you are ready to install your finished scissor truss, be sure to follow all safety precautions.