Attic trusses are much the same as trusses on almost any other kind of roof except for one key characteristic: attic trusses are designed in such a way that the attic can also be a proper room in itself without the braces of the trusses making movement around the room difficult. An attic truss, therefore, has a large four-sided opening in the middle of it with the braces confined to each side of the truss, allowing people to easily move between the beams. Building and installing an attic truss is tricky and time-consuming, but no more so than any other trusses. You will need to have a high degree of familiarity with woodworking and roofing to be able to do the job yourself.
Step 1 – Make Preparations
You will first need to determine the roof loads that the trusses will have to support. You will need to take into account the entire weight of the wood in addition to any possible extra weight, such as from snowfall. The number of trusses you need will partly depend on this. When you know how many trusses you need, buy the appropriate quantity of timber. Keep in mind that for each attic truss, you will need to have a bottom chord, two top chords and straight and diagonal braces. Attic trusses can come in various styles, with the vertical posts flanking the walkway or set further apart.
Step 2 – Cut the Wood
Cut the wood for a standard room-in-attic truss. This provides a four-sided opening in the middle. First, cut the bottom chord and the two top chords. The top chords need to be angled at the ends so that they fit together as they should. You will also need two vertical supports and a crossbar to go above these. This beam will also connect to both of the top chords and will need to be angled at both ends. The vertical beams need to be angled at the top end, where they will connect to the top chords. Finally, there will need to be additional braces, including two for each side of the truss, dividing the triangular shapes into three sections. There should also be an additional supporting vertical beam at the top center.
Step 3 – Assemble the Truss
The trusses should be assembled using gussets attaching each point together. Gussets can be made of metal or wood, with the former being considerably stronger. You can cut the gussets yourself so that they are the exact size for this application. Attach the gussets over all of the connections between the beams, and nail them in place.
Step 4 – Install the Truss
Install each truss only after it has been completely assembled. Hoist each one into position, and make sure that the ground bracing is already prepared to support the first truss. When installing the truss, use temporary braces until it is properly fixed in place. Finally, bolt the trusses down to the floor, making sure that they are attached to the structure of the house.