Roof Trusses for Strength and Span

Wood, Steel, and Engineered Timbers Roof trusses, historically composed of wood with metal connector plates, now have competition. As steel-framed homes catch on, so have all steel roof trusses. O’Connor says that to date steel roof trusses are typically reserved for the light commercial and industrial markets, with wooden trusses still dominating home construction. Engineered wood products such as I-joists have also made a big surge in the market. “They can be used almost like framing lumber, but unlike conventional lumber, they’ll span up to 60 feet in length,” O’Connor says. Wood roof trusses with metal connectors can also be treated with fire retardant and have an “excellent fire rating,” according to O’Connor. Wood trusses with metal connectors, from a budgetary and quality standpoint, are the price point winners,” according to O’Connor. When they are properly engineered and put together, the wood roof truss with low-cost connector plates will perform to engineered lumber parameters. “So they are a nice, low-cost solution to framing problems,” O’Connor says. Coupled with hurricane straps for fastening the trusses to the walls, the roof system is typically better than any stick-built roof, according to O’Connor. A strong roof depends on its ties. Members must be tied to one another and to the outer walls so that loads can be transferred and building connections maintained. Strap it Down for Strong Structures From a best practice standpoint, connecting roof to truss and truss to the rest of the house is critical to creating a storm-ready home. O’Connor says using the appropriate metal connector hardware to fasten the truss to the top plate of the wall, whether it is a block or wood-framed wall, will create a strong tie-in that can withstand almost any load. The key is to look at the building as a complete system. “Usually you have one person designing the walls and another designs the roof and nobody ties the two together other than the building official,” Grundahl says. “It is imperative that these two come together properly.” Installation is best left to professionals who come on site with a truck-mounted crane to place roof trusses. Once in place and connected, trusses may not be cut, notched, or altered in any way in order to maintain their engineered integrity. Proof after the Storm The stricter building codes have already stood the test of time. O’Connor says homes built after Hurricane Andrew came through subsequent storms much better than those built before. “Entire roofs or sections of roofs were not blown off. Most damage to the homes was caused by flying debris.” “Whenever contractors are made to do things to more stringent codes, everybody complains at first, but then when they see the results and how it has saved buildings, they figure that making the change was the right thing to do,” O’Connor says.

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