Framing Tricky Truss Roofs
When building houses with trusses made for hips and valleys, careful planning and job-site organization are key to an efficient installation.
Synopsis: Over three-quarters of the roofs on new homes in the United States are built with trusses. For gable roofs, you simply need lots of the same kind of truss. For roofs that include hips and valleys, however, you may need trusses in dozens of different configurations. Paul Johnson and Nathan Young, building contractors in Portland, Ore., explain in this article their process of installing trusses for a house with a complex roof. They stress that before the trusses even arrive at the job site, it’s important to make a plan for delivery that ensures that there is adequate space for the delivery truck and that identifies the spot where the trusses will be unloaded. The truss company includes a plan with the truss package that should be followed carefully. The builder, however, will need to decide where to start. Johnson and Young usually begin with a girder truss, then proceed with the installation in sections. They provide guidance for installing blocking, stick-framing certain areas, shopping for a truss supplier, and modifying a truss. A color-coded photo illustrates the types of trusses Johnson and Young used on one project: hip, girder, jack, and valley.
It’s estimated that nearly 80% of the roofs on new houses are framed with trusses rather than conventional rafters. The reason for this is simple: roof trusses are faster to install, which lowers labor costs and results in quicker occupancy. In seismically active areas, such as the Pacific Northwest region where we build, using trusses is generally the simplest way to build a complex roof that satisfies code and local inspectors. It has also been our experience that perhaps one framing crew in a dozen could efficiently stick-frame the complicated roof of a custom home like the one shown here.
On this job, the architect sent his detailed roof plan to the truss company, which used computer software to design the individual trusses and to plan the layout. Once the foundation was in place, a representative from the truss company checked the site for factors that would complicate delivery and took final measurements of the foundation. The truss package was delivered 10 days later.
Make a plan for delivery
Depending on their length, trusses may arrive on a flatbed truck that has an on-board crane, or they may be delivered on a semi and unloaded with a separate crane.
On this project, they came on a 60-plus-ft. flatbed with an on-board crane. Even with this big truck, the trusses still stuck out the back by 10 ft., which meant that the truck was blocking a lane in the street. Further complicating matters, the truck driver, who was also the crane operator, had to navigate around trees to get the trusses off the truck, which prolonged the delivery process.
It wasn’t a problem on this job, but the parking area for the truck needs to be wide enough to accommodate the stabilizers for the crane. Because the truck is heavy, the truss company may require a damage waiver to protect it from lawsuits if the truck breaks a paved driveway. We often use scraps of LVLs under the stabilizers to help spread the load when the truck is on concrete or asphalt.
The truss company is responsible for getting the trusses to the job and will set the bundled trusses on the ground, or on the wall plates if they can reach, but they won’t spend the time to set individual trusses. On most residential projects, this isn’t a problem, but on commercial and large residential jobs with especially long or tall spans, it’s worth the cost of hiring a crane to set individual trusses while the framers brace them. We’ve also been on jobs where the delivery truck can’t get the trusses on the roof because of their size or because of poor access. In these situations, we bring in a smaller crane or an all-terrain forklift to lift trusses individually or in bundles.
Precise layout and understanding of the truss plan is the key to making a truss roof with hips and valleys that come together. A good truss manufacturer provides a detailed layout, bracing instructions, and all the necessary hardware. However, you’ll need a basic understanding of roof framing for the plan to make sense. Fortunately, truss and stick-frame roofs share much of the same terminology.
For more photos and information on framing tricky truss roofs, click the View PDF button below.
From Fine Homebuilding #225
