I-Joist

Engineered joists that are strong and use less lumber than solid wood joists. Wooden i-joists are often made with two solid lumber pieces along each edge, joined together with a sheet of plywood, oriented strand board (OSB), or metal triangles to keep the edge pieces apart and provide bending strength. Engineered i-joists keep their shape more than solid wood joists, with less bowing, twisting, or splitting.

Look for I-joists made with Forest Stewardship Council (FSC) certified wood. Also consider the glues used in the plywood or OSB portion, looking for low-VOC and formaldehyde-free products.

An I-joist can provide greater structural strength for lower weight and less materials used, compared with solid wood joists. I-joists are often used to create thicker walls and roof spaces that can hold more insulation, making it possible to save more on energy bills.

The engineered wooden i-joist was invented in 1969. By 2005, it was used for up to half the light wood floors in the United States.