Are roof trusses better than roof rafters (stick framing)?
Wednesday, July 18, 2018
Wood trusses have been the standard for residential roof construction for many years now. Although they may cost more than the lumber for rafters when used for shorter spans, trusses save a tremendous amount of onsite labor, so the final cost of materials and labor is less. Also, a truss made from 2x4 lumber can easily span further than the largest dimensional lumber available at a local lumberyard.
So why are there some houses still being built, at least partially, with a stick framed roof? It’s difficult to get as dramatic a ceiling under a scissor truss as a roof framed with rafters, and large exposed rafters can be a dramatic architectural feature of a room. Another situation where rafters would be preferable is a porch addition to a home with a shed (single slope) roof, especially if you plan to expose the underside of the roof sheathing.
The complicated rooflines of many new homes that would frustrate even the most experienced carpenter are easy to build with trusses. You just follow the layout plan provided by the manufacturer and all the roof valleys and coffered ceilings fall into place correctly without any calculations. But stick framing a roof is decidedly an “old school” art, and builders that still know how to calculate the dimensions and cuts for a hip roof are justifiably proud of their knowledge of the craft.
We also sometimes find problems with truss roof structures during a home inspection due to poor storage or handling during construction of the home, or improperly repaired damage later from a fallen tree branch.
There are also occasions when a stick-framed addition with a shed roof has been added to a home with a truss-framed main roof, and one end of the rafters bears on the top chords of the trusses. Because trusses are not engineered to handle any additional loads like this, it is a serious defect. While the roof rafters of a home addition can intersect the roof trusses in order to merge the sheathing of the two roofs, the bearing points of the rafters should be framed down to the common bearing wall between the two structures.
Also, see our blog post How much of a roof truss can I cut out to make a storage platform in the attic?
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To learn more about roofs and attics, see these other blog posts:
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