Our contractor plans to use “Scissor trusses” to create a vaulted ceiling in our family-room addition. What is a scissor truss?
A—You’ve probably seen more conventional roof trusses being installed on new homes under construction. They are engineered and factory-fabricated structural members designed to effectively span wide areas, often without center support. Typically with a triangular shape, they incorporate the roof rafters and ceiling joists in a single element, strengthened by diagonal bracing. Conventional vaulted ceilings require either a structural ridge beam to carry the load at the top of the rafters, or collar ties and/or wall buttresses to resist the outward thrust of rafters trying to rotate down and out. These structures, often seen in churches and auditoriums, are expensive to build, and a challenge to ventilate properly because of a lack of attic space between ceiling and roof. A scissor truss gets its name from the shape. Instead of a flat bottom cord, it is angled to create a sloped ceiling, but at a somewhat flatter pitch than the roof. This forms an acute angle, or scissor shape between me
