Pipes, ducts, cable trays and sprinkler lines in a building are almost always hung from the slab or steel above using a small family of parts: anchors, threaded rods, slotted channels, channel nuts and clamps. Here is how these parts fit together and what to check before you order.

The basic hanging system

1. Top fixing: a drop-in anchor in a concrete slab, or a beam clamp on a steel beam.
2. Threaded rod: carries the load down to the service. Common sizes are M8, M10 and M12, usually supplied in 1, 2 and 3 metre lengths and cut to size on site.
3. Support at the bottom: a pipe clamp for a single pipe, or a slotted channel (strut) as a trapeze for several pipes, a duct or a cable tray.
4. Nuts and washers: to lock everything in place and allow level adjustment.

Choosing each part

Anchors in the slab

Drop-in anchors are the usual choice for overhead rods because the rod can be screwed in and replaced later. Match the anchor thread to the rod size, drill to the depth on the data sheet and set the anchor fully with the correct setting tool. For heavy or vibrating loads, or near slab edges, your engineer may specify wedge or chemical anchors. Our anchor selection guide explains the differences.

Threaded rods

Choose the rod diameter from the load and the hanger spacing in your design. As a general pattern, M8 is used for light services, M10 for medium pipes, trays and ducts, and M12 or larger for heavy pipes and multi-tier trapezes. Use zinc-plated rods indoors and hot-dip galvanised or stainless rods in wet or outdoor areas.

Slotted channels (strut)

Channels with a continuous slot, such as 41 × 41 mm and 41 × 21 mm profiles, let you bolt clamps anywhere along their length. They are used as trapeze supports, wall brackets and frames. Deeper or back-to-back channels carry more load over wider spans.

Channel nuts

Spring-loaded channel nuts drop into the slot and turn to lock behind the lips, so you can position clamps and rods quickly. Match the nut thread to the rod or bolt.

Pipe clamps

Rubber-lined clamps reduce noise and vibration on water and HVAC pipes and protect copper and PVC. Unlined clamps suit steel pipes, conduits and general use. Make sure the clamp size matches the pipe outer diameter, not its nominal bore.

Beam clamps

Clamp onto the flange of a steel beam with a threaded hole for the rod. No drilling or welding is needed, which protects the structure and its paint.

Installation tips

• Lock every adjustable joint. Use a nut and washer on both sides of the channel, and add a lock nut or spring washer where there is vibration.
• Keep rods vertical. Angled rods carry extra load and can bend. Add bracing where your design requires it, including seismic bracing in buildings that need it.
• Support near changes in direction such as bends, tees and valves, and on both sides of heavy items.
• Cut rods cleanly and file the end so nuts start easily. Touch up cut ends of galvanised rods with zinc-rich paint.
• Allow for movement on hot-water and steam pipes with roller or sliding supports where specified.

Order checklist

• Anchor type and size, and quantity per hanger point.
• Threaded rod size, length and finish.
• Channel profile, length and finish, plus end caps if exposed.
• Channel nuts, hex nuts and washers in matching sizes.
• Pipe clamp sizes (by pipe outer diameter), lined or unlined.
• Beam clamps, if hanging from steel.

Laying cables as well? Read our cable tray buying guide.

This guide is general information for buyers. Always follow the anchor or fixing manufacturer's data sheet and your project engineer's design for load-bearing and safety-critical work.