What are Bar Joists?

Let's start at the beginning with what a bar joist is and what it's used for. Steel joist is a structural framing component used in floors and roofs to provide added support and even weight distribution.

Bar joists provide light weight strength that is able to span long distances, between girders, typically running in the same direction as a beam, or even acting as a replacement for beams. A metal joist consists of two parallel chords which are joined to each other via a triangular framework of intersecting supports known as webbing.

How to Attach Unistrut to Bar Joist with Beam Clamps

Unistrut Bar Joist Attachment using Beam Clamps

Now that we know what bar joists are, we need to know what the best way to connect our Unistrut supports to them is. One way to attach Unistrut channel perpendicular to joist steel is through the use of Unistrut joist clamps, more commonly referred to as window clamps, such as the P2785, P2786, and P2787. These clamps are manufactured with different u-bolt lengths to acommodate various channel heights and are always used in pairs.

When attaching beam clamps to joist, the clamps are attached to the bottom chord of the bar joist. Channel can be attached either above or below the chord.

Download this Handy Connection Guide

UNISTRUT-JOIST-CLAMP: How to Attach Unistrut to Bar Joist Using Beam Clamps

Which Beam Clamp Should I Use?

Unistrut Joist Clamp

The P2785-2787 Unistrut joist clamps can be used on beams with up to 3/4" flanges. They are used in pairs only, with a design load each of 1000 pounds. Clamps include 3/8" hex nuts and u-bolt. They are designed to be used with 1-5/8" width Unistrut single or double channel.

  • Unistrut P2785 can be used with channels: P1000, P1100, P2000, P3000, P3300, P3301, P4000, P4001, P4100, and P4101
  • Unistrut P2786 can be used with channels: P1001, P1101, P2001, P3001, P5000, and P5500
  • Unistrut P2787 can be used with channels: P5001, and P5501

Are There Other Methods of Attaching Unistrut to Bar Joist?

Yes there are! This is just the first blog in our three part series on how to connect bar joist to strut channel. Though using Unistrut joist clamps to attach Unistrut channel to a bar joist may be the most common method of connection, there are several other methods which we will go over in more detail in later blog posts.

Ultimately, the method that works best for your specific project may depend on a few key factors, such as:

  • What mechanical, electrical, plumbing and HVAC elements, or obstacles, are already in place
  • What has been requested by the project engineer

Other methods of Connecting Unistrut Channel to Bar Joist include:

  • Threaded Rod
  • Joist Wrap

RESOURCES

Installation

Download Connection Guide for UBS-JOIST-CLAMP
UBS-JOIST-CLAMP: Unistrut Bar Joist Beam Clamp Assembly (3.47 MB)

Submittals

Unistrut P2785 Product Submittal (305.12 kB)

Unistrut P2786 Product Submittal (307.70 kB)

Unistrut P2787 Product Submittal (310.01 kB)

Drawings

Unistrut BIM / CAD Library

DISCLAIMER

STANDARD DETAILS ARE FOR REFERENCE AND DESIGN PURPOSES ONLY, AND ARE NOT INTENDED FOR USE AS FULLY ENGINEERED SYSTEMS. ENGINEERED SYSTEMS MUST TAKE INTO ACCOUNT ACTUAL SITE CONDITIONS (SUCH AS: LOAD, ELEVATION, SIZE, SPACING, BUILDING STRUCTURE, EXISTING MEP STRUCTURES, ETC.) AND BE PURCHASED THROUGH UNISTRUT BUFFALO SUPPORTS, A DIVISION OF EBERL IRON WORKS, INC. 128 SYCAMORE STREET, BUFFALO, NEW YORK 14204. CONTACT UNISTRUT BUFFALO SUPPORTS: 1 (800) 285-3056 UNISTRUTSTORE.COM/REQUEST-QUOTE FOR A CUSTOM QUOTE TAILORED TO YOUR JOBSITE/PROJECT.