To make vision become reality, you have to work from the bottom up. Foundations and what comes next—the load-bearing support and flooring elements—beg answers to critical questions. When do you use an engineered wood system and when do you opt for trusses? What’s the difference between the two? How do you know you’re getting a quality product?
Today’s flooring plans typically call for either I-joists or trusses
- I-joists are basically long webs of OSB with flanges of dimensional lumber or laminated veneer lumber. Flanges bear weight while the OSB web portion prevents shearing. They come in various sizes that comply with standard construction requirements. Rim boards around the perimeter tie the system together.
- Trusses are assemblies made of dimensional lumber oriented flatwise and joined with toothed steel plates. They consist of top and bottom chords connected by internal members that form the web. Floor trusses use parallel top and bottom chords. In roof trusses, top chords descend at an angle from the height and pitch established by an internal king post.
The two technologies differ in a number of ways
- While I-joists can span considerable distances—up to 30 feet or more—trusses can cover even greater distances thanks to the way they’re constructed.
- I-joists are limited in the placement and number of ventilations the OSB can sustain without compromising load-bearing capacity and stability. In contrast, the open nature of a truss web can easily hold electrical, plumbing, and mechanical systems with little to no adjustment needed. This can be especially helpful when installing heated floors to combat cold Wyoming winters, for example.
- If certain areas require extra load-bearing capability, custom trusses can be designed to handle the additional weight.
- For remodels or additions, variations in truss ends and chord bearing make it easier to match existing floor heights.
- Since I-joists are standardized, they’re usually in stock and readily available. Trusses, however, are fabricated to project requirements and delivered onsite. Trimmable trusses allow for standardized production with custom adjustment onsite. Generally, installation for trusses tends to be quicker than that for I-joists.
- Some building designs may not allocate sufficient depth space for floor trusses, making I-joists a better option.
- For balconies or other extensions, trusses can include the necessary cantilever.
- Both I-joist and truss manufacturers design their products to reduce floor squeaks and eliminate crowning issues that can cause problems later.
Both trusses and I-joists have proved their functionality and are used not only for flooring systems but also roofing. These wood products offer great range, strength, and durability. Let your local Builders FirstSource experts in Cody help you with your new construction or addition.