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Bob explains the engineering and construction of the truss system supporting the roof of the accessible home in the Roxbury section of Boston.
Bob Vila: Â All of the framing and the partitioning are now complete on this second floor. We’ve got two bedrooms. The street side bedroom is about a 12 x 12 with a good size clothes closet and another storage closet over there.
Here in this keyhole, we have a very spacious linen closet, a deep storage closet, and luggage, whatever. Then an average size bathroom in here, which is getting it’s blocking in place. The back bedroom has a big walk‑in closet, a really terrific one, about 6 x 6.
The main thing I want to show you is look up. This is what we’re talking about in terms of a roof truss system. We’re in the process of putting the shingles on already, but this is a 2 x 4 truss system that went up very quickly. Let’s watch.
Bob  On this project, we’re using a structurally engineered truss system for our roof. From the architects’ plans, rafter segments are constructed based on the pinch and load of the roof. The prefabricated trusses are delivered to the job site ready for installation. The crew lifts each truss onto the roof and moves it into position.
These trusses are constructed from 2 x 4s, ordinarily 2 x 4s are too small for use as roof rafters, but the engineered construction of each truss allows the use of smaller dimensional lumber in this application.
Each truss is tacked into place using eight‑penny nails. Then, these engineered metal braces are placed between the trusses to tie the system together. These joint plates tie the truss pieces in place and are the key to the strength of the system.
The trusses are temporarily held in place with bracing until the sheeting is applied to the roof. Assembling the roof structure with this system is very fast. A crew of about half a dozen workers can raise the truss system and sheet the roof with plywood in a single day. Let’s watch.
Bob: Â Once we got all the plywood sheeting in place, we’re ready to bring the shingle crew aboard. As you can see, they’ve got a good start on the job. We’ll be taking a closer look in a minute.
