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What is an I-Joist?

An I-Joist is a high-strength engineered wood product used in construction for floors and roofs. Its 'I' shape, resembling the letter, consists of a top and bottom flange connected by a vertical web, offering robust support with less material than traditional joists. Intrigued by how I-Joists can enhance your building project? Discover their unique benefits and applications as we explore further.
Harriette Halepis
Harriette Halepis

An I-joist is a type of engineered wood support that is often used in place of a traditional wood joist. The I-joist is used in many modern constructions from homes to industrial spaces. Even though most of these joists are relatively small, a typical I-joist is capable of a large amount of pressure.

The average I-joist is comprised of two main parts: the flange and the web. The piece of plywood, lumber, or board that is placed in-between each flange is known as a "web." The two pieces of wood that are placed on the top and bottom of the web are known as flanges. As the flanges hold the web together, the web also keeps each flange in place. The I-joist gets its name from the shape that is created when the web and flanges have come together to form an "I."

Man with a drill
Man with a drill

Once the web and flanges have been cut to builder specifications, waterproof industrial glue is placed inside of each flange. After inserting the web into the flange area, the web is then glued into the flange. The completed product is then allowed to dry at room temperature for one to two hours. The size and depth of an I-joist can greatly differ depending upon the amount of weight that a joist must support.

This type of joist was originally created to provide floor board and beam support. Prior to the invention of the I-joist in 1969, solid lumber was used to support both floors and beams. While a solid piece of lumber may bow, crack, twist, or warp, a specially made joist will not succumb to any wear due to pressure. Further, floors that are installed using I-joists will not squeak as much as floors that do not have I-joists.

In every manner, these joists are entirely effective. Only, an I-joist that has not been installed correctly could be detrimental. Before installing any kind of joist, manufacturer instructions must be read carefully. Many people make the mistake of inserting the web into the flanges incorrectly, and this can cause the joist to break.

Also, a joist must have proper time to dry before attempting to install this type of support. If a joist is not allowed to dry properly, the result may be floors that creak. While I-joists can be installed by homeowners, hiring a professional contractor to ensure that these joists are properly installed is a wise idea.

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