Cold-formed steel (CFS) trusses can be an economical framing option for many buildings, and are often the most economical option for those having a steeply sloped roof. Some advantages of CFS trusses are that they have an excellent span-to-weight ratio, can be shop-fabricated into custom shapes, and are non-combustible. Despite these advantages, the use of CFS trusses on inhabited building projects funded by the Department of Defense (DoD) can be challenging because of the requirements imposed by Unified Facilities Criteria (UFC) 4-010-01, DoD Minimum Antiterrorism Standards for Buildings.
One of the primary design strategies of UFC 4-010-01 is to increase the standoff distance between buildings and potential explosive threat locations. In 2012, UFC 4-010-01 was amended to correlate the standoff distance at which no analysis for blast loads is required with the exterior wall and roof construction type. Buildings constructed of heavier and more robust materials, such as reinforced concrete or masonry, are permitted to have smaller standoff distances than buildings constructed of lighter materials, such as wood or CFS studs, as long as the structural design complies with UFC-prescribed detailing requirements. Provisions for several wall and roof systems are included in the UFC, but any wall or roof type that differs from the prescriptive requirements must be analyzed for blast loads. One roof framing system not explicitly addressed is CFS trusses with metal roof deck.