Dimensional lumber has long been a workhorse for framing floors, roofs, and everything in between due to its accessibility, durability, and ease of shipping. Other framing systems like trusses and engineered wood, however, are changing construction in significant ways like extending span lengths and expanding scale; cutting construction time; and allowing for greater compatibility with the requirements of electrical, mechanical, and plumbing systems, for example.
The engineered I-joist originated in Idaho in the late 1960s and has spread to become a global mainstay in the industry. The joists mimic the contours of steel I-beams, using a web-and-flange design. The web is typically OSB—oriented strand board—while the flanges can be laminated veneer lumber or dimensional lumber. The flanges are able to bear loads while the web prevents shearing.
I-joists have become popular for both the residential and light-commercial flooring and roofing industries because they’re straight and true. I-joists bypass crowning issues that can slow construction and result in problems with bowing or sagging later. They’re also usually readily available in all the depths and sizes contractors need.
Trusses take a different approach, using dimensional lumber joined with toothed steel plates to create a load-bearing support:
- Chords make up the top and bottom truss boards. In flooring, the top and bottom chords run parallel to each other to ensure a flat, level surface. In a roof truss, top chords descend on an angle.
- Web is the term used for the internal members or boards connecting the top and bottom chords.
For strength and stability, chords and internal members are assembled flatwise rather than edgewise. Because of the way they’re constructed, trusses can span greater distances than I-joists, and their open areas let other systems share space without compromising strength. Since they’re prefabricated specific to job measurements, they’re ready to be dropped into place, shortening construction times and simplifying the logistics end of a job.
The system you choose will depend on the distances you need to span, the weights and distribution of the loads that the supports will have to bear, the additional systems you want to install in your home, your budget and time frame, and what your building plans and blueprints will allow. If you yearn to start breaking ground, make sure you’re taking advantage of your best options. Stop by one of our local Builders FirstSource locations in Boise, Meridian, Twin Falls, McCall, or Post Falls, and let our experts take a look at what you envision now and for the future.