Frame a Strong, Stable Floor With I-Joists
Engineered floor joists are straighter, faster, and flatter, but they aren't installed the same way as dimensional lumber
When Rhode Island builder John Spier is getting ready to frame a floor, he doesn’t place an order for dimensional lumber. He calls in an order for I-joists. These engineered floors joists are pricier than regular lumber, but because they are straighter and flatter, they can be installed more quickly. That means big savings in labor costs. I-joists are a component of an engineered floor system, and they require a specific installation process and hardware, including joist hangers. After the joists are in place, a subfloor locks together the layout.
<p>Manufactured I-joists are used in about 45% of new wood-frame construction, and that amount is expected to rise. I can’t remember the last time I framed a new floor with dimensional lumber. To me, I-joists make more sense. They are straighter, stronger, and lighter, and they span longer distances than ordinary 2xs. They are also a more-efficient use of resources because they can be manufactured using lesser-quality trees. Of course, I-joists cost a bit more, but they also are much easier to install, meaning I get a big savings in labor. Then again, nothing is perfect, and I-joists have a few disadvantages compared to standard dimensional lumber. They don’t cope well with careless handling, they are more sensitive to moisture, and they shouldn’t carry any load until they are fully sheathed. They also aren’t as amenable to job-site change orders, and many lumberyards don’t stock them.</p>
<p>I-joists are part of a carefully planned floor system</p>
<p>With I-joists, systemis the operative word. A floor framed with I-joists is designed as a package with all its components specifically located in the overall structure. This is different from…