Typical K-Series Roof Joist Construction

Open Web Joists

• There are three types of steel joists: K-Series, LH-Series and DLH-Series. These joists go by various technical names, including open web joists and open web trusses. The interior structure of these joists looks much like that of a truss – both contain a series of angled support bars in repeating triangular shapes. However, trusses assume a generally triangular shape, while open web joists assume an elongated, rectangular shape. As such, open web joists exist to support flat roofs, while trusses support sloped roofs. Open web joists also generally support relatively light loads, such as basic metal roof sheeting found on sheds or warehouses.

K-Series Joists

• A K-series joist consists of two steel I-beams with an interior network of supports. An I-beam is a steel structure with broad, flat top and bottom pieces and a tall, thin piece of steel placed perpendicularly between the top and bottom. Seen from the side, these beams resemble an uppercase letter “I.” Between the two I-beams in a K-series joist runs a series of thin support beams that assume various triangular forms. The actual shape of a K-series joist support depends on the manufacturer. K-series joists exhibit a depth, or height, or 8 to 30 inches, available in 2-inch increments, and a length of up to 60 feet.

Roof Joist Structure

• Typical K-series joist roofs assume an extremely simple form. When you build an outdoor structure such as a shed, workshop or barn, erect large steel support beams from wall to wall in a single direction, such as north-south or east-west. Your joists serve as additional support members running between these primary support beams. After installing the beams, place joists between them, running the opposite direction. Install K-series joists at even intervals. The number of K-series joists you need depends on the tensile strength of the joists, as stipulated by the manufacturer, and the amount of weight support you need for the roof. The number of primary support beams you install also affects the number of joists you need.

Connectivity

• Connectivity is very important in K-series roof joist construction, as secure connections bolster joist strength and performance. In this context, connectivity refers to the way in which you attach your joists to the primary beams of your roof support network. Ideally, you should purchase your K-series joists at a depth that fits perfectly with your primary support beams. Upon installing the primary support beams, attach the top I-beam to the top of the primary beam with bolts recommend by the manufacturer. Attach the bottom I-beam of the joist to the upper side of the bottom of the primary support beam, using the same bolts. When running an open web joist from a beam to a wall, embed the joist in the material of the wall and anchor it with bolts.

Construction Techniques

• You may need heavy lifting material for your K-series joists, depending on the size of your structure. With short joists, such as those spanning an 8-foot distance, you may need only a few helpers and a simple pulley system. However, long joists, such as a 20-foot K-series unit, may require heavy lifting equipment to maneuver into place. Contact a professional contractor or builder to help you with a large scale project, such as a barn, to avoid injuring yourself or others during the process. Other than lifting considerations, joist installation requires the use of basic tools, including heavy-duty drills.