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.

Cable trays carry power and data cables through buildings, plants and service shafts. The right tray keeps cables cool, supported and easy to add to later. This guide covers the main tray types, finishes, sizing and the accessories you should not forget when ordering.

Types of cable tray

Perforated tray

A solid sheet-metal channel with punched holes along the base. The holes let heat escape and give many points to tie cables. Perforated trays are the most common choice for small and medium power cables, control cables and mixed runs in commercial buildings and factories.

Ladder tray

Two side rails joined by rungs, like a ladder. It gives excellent ventilation and is strong over longer spans, so it is used for heavy power cables and long horizontal runs such as in plant rooms, substations and industrial sheds.

Raceway or trunking (covered tray)

A closed tray with a cover. It protects cables from dust, water dripping from above, falling objects and tampering, and looks tidy where cables are visible. Ventilation is lower, so cable sizing must allow for it.

Wire mesh tray

Light welded wire baskets, popular for data, CCTV and low-voltage cables above false ceilings and in server rooms. Easy to cut and bend on site.

Choosing the material and finish

Sizing the tray

1. List the cables that will run in the tray, with their outer diameters.
2. Add up the cable widths if laid in a single layer, or the total cross-section area if bunched.
3. Leave room. Do not fill a tray to the brim. Keeping it roughly half full helps cables run cooler and leaves space for future circuits. Your electrical designer may specify an exact fill limit and derating.
4. Pick a standard width and depth. Common widths are 100, 150, 200, 300, 450 and 600 mm, with side heights such as 25, 50 and 75 mm.
5. Check the sheet thickness and support spacing against the manufacturer's load table. Heavier cable loads need thicker sheet or closer supports.

Supporting the tray

• From concrete ceilings, trays are usually hung on threaded rods with drop-in anchors, with a slotted channel or angle as a cross-support (a trapeze).
• On walls, use wall brackets or cantilever arms fixed with suitable anchors.
• From steel beams, use beam clamps so you do not need to drill or weld the structure.
• Add a support close to every bend, tee and joint, as these are the weak points.

See our step-by-step guide to hanging MEP services with threaded rods and channels.

Accessories checklist

• Bends (90° and 45°), tees, crosses and reducers.
• Couplers or joint plates with nuts and bolts.
• Covers for exposed or vertical runs.
• Earthing continuity links across each joint, and the tray system bonded to earth as per your electrical design.
• Cable ties or clamps, and edge protection where cables leave the tray.

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.

On site, people ask for "MS bolts", "GI bolts" or "SS bolts". These words describe the material and the protective coating, and choosing the right one is mostly about where the fastener will be used. Here is a plain-language comparison to help you choose.

What the terms mean

• MS (mild steel): plain carbon steel with no corrosion protection other than a light oil, often called "black" finish. Strong and cheap, but it rusts quickly if left exposed.
• Zinc-plated or electro-galvanised (EG): steel with a thin layer of zinc applied by electroplating, often followed by a clear, blue, yellow or black passivation. Typical zinc thickness is only about 5 to 12 microns.
• GI or hot-dip galvanised (HDG): steel dipped in molten zinc, giving a much thicker coating, usually around 45 to 85 microns on fasteners. It looks dull grey and slightly rough. "GI" (galvanised iron) is the common trade name.
• SS (stainless steel): steel alloyed with chromium and nickel, so the whole fastener resists rust. SS304 (A2) is the common grade and SS316 (A4) is used for harsher, salty or chemical environments.

Side-by-side comparison

Which one should you use?

Inside a building, in dry areas

Zinc-plated fasteners are usually enough for false ceiling supports, cable tray hangers in dry shafts, furniture and panel work. They look neat and cost little.

Outdoors, terraces, basements and wet areas

Use hot-dip galvanised bolts, nuts, threaded rods and anchors. The thick zinc layer protects for years even when the surface is scratched, because zinc corrodes first and protects the steel underneath.

Near the sea, in pools, food plants and chemical areas

Use stainless steel, and choose SS316 (A4) where there is salt or chlorine.

Steel structures that will be painted

Black MS bolts are acceptable when the whole joint will be primed and painted, but galvanised bolts last much longer if paint is damaged.

Things that cause trouble on site

• Mixing metals. Stainless bolts in aluminium, or zinc-coated parts touching copper, can corrode faster because of galvanic action when wet. Use matching materials or insulating washers.
• Using plain nuts on HDG bolts. Hot-dip galvanised nuts are tapped slightly oversize to fit over the thick coating. Always buy HDG bolts and nuts as a set.
• Welding galvanised parts. Zinc fumes are harmful. Weld only with good ventilation and proper protection, and touch up the weld area afterwards with zinc-rich paint.
• Expecting plating to last outdoors. Bright zinc-plated fasteners often show white rust within months outside. That is a finish problem, not a material defect.
• Stainless galling. Stainless nuts and bolts can seize when tightened fast or dry. Tighten steadily and use anti-seize compound on larger sizes.

Also see our guide to bolt grades 4.6, 8.8 and 10.9.

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.

Picking the wrong anchor is one of the most common reasons a fixing works loose, cracks the wall or fails an inspection. This guide walks through the main anchor types sold in India and a simple way to choose between them for concrete, brick and block.

Start with three questions

1. What are you fixing into? Solid concrete, solid brick, hollow block, AAC block or plasterboard all hold anchors differently.
2. What load will it carry, and in which direction? A pipe hanger pulls straight down out of the ceiling (tension). A bracket on a wall mostly pushes sideways (shear). Vibrating machines and moving loads need more margin than a static shelf.
3. Where will it live? Dry indoors, damp basement, outdoors, or near the sea. This decides the finish.

The main anchor types

Wedge anchors (through bolts)

A threaded stud with an expanding clip at the bottom. You drill a hole the same diameter as the anchor, tap it in through the fixture and tighten the nut, which pulls the clip up and wedges it against the concrete. Wedge anchors give high holding power in solid concrete and are the usual choice for heavy brackets, machinery bases, railings and structural steel cleats. They are not suitable for brick or hollow block.

Sleeve anchors

A bolt inside a split steel sleeve. Tightening the bolt expands the sleeve along a longer length, so it is more forgiving than a wedge anchor in solid brick, stone and medium-strength concrete. Good for door frames, gates, rack uprights and general fixing where the base material is not perfect.

Drop-in anchors

An internally threaded steel shell that sits flush inside the hole. A setting tool drives a plug down to expand it, after which you screw in a threaded rod or bolt. Drop-in anchors are the standard way to hang threaded rods from concrete ceiling slabs for cable trays, ducts, pipes and false ceilings, because the rod can be removed and refitted later.

Chemical (resin) anchors

A threaded rod set in injected or capsule resin. The resin bonds to the hole wall instead of pushing against it, so there is very little expansion stress. That makes chemical anchors the right choice close to edges, in closely spaced groups, for heavy or vibrating loads, and in hollow block when used with a mesh sleeve. They need a clean hole and full curing time before loading.

Nylon plugs and frame fixings

Nylon wall plugs with wood or self-tapping screws are fine for light loads such as conduits, light fittings, small boxes and signage. Longer nylon frame fixings work well for window and door frames in brick and block.

Quick selection table

Installation rules that make the biggest difference

• Use the correct drill bit. For wedge and sleeve anchors the bit diameter normally equals the anchor size marked on the pack. An oversized hole is the most common cause of anchors spinning or pulling out.
• Drill deep enough and clean the hole. Blow out or vacuum the dust. Dust left in the hole reduces holding power, and for chemical anchors it can ruin the bond completely.
• Respect edge distance and spacing. Expansion anchors placed too close to a slab edge or to each other can split the concrete. Follow the minimum edge and spacing values on the anchor data sheet. If you cannot meet them, use a chemical anchor.
• Tighten to the specified torque. Under-tightened expansion anchors do not set properly. Over-tightening can crack the base material or strip the thread.
• Do not reuse a failed hole. Drill a new hole a safe distance away, or switch to a chemical anchor.

Choosing the finish

• Zinc-plated (bright or yellow): dry indoor areas.
• Hot-dip galvanised: outdoors, damp areas and exposed structures.
• Stainless steel (A2/SS304 or A4/SS316): coastal sites, food plants, swimming pools and anywhere with chemicals. A4 is the better choice near the sea.

Read more in our guide to GI, MS and stainless fasteners.

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.

The numbers stamped on a bolt head, such as 4.6, 8.8 or 10.9, tell you how strong the bolt is. Reading them correctly helps you buy the right bolt for the job and avoid paying for strength you do not need, or worse, using a weak bolt where a strong one is required.

What the two numbers mean

Steel bolts are graded by property class under ISO 898-1 (adopted in India as IS 1367 Part 3). The class has two numbers separated by a dot:

• The first number × 100 gives the nominal tensile strength in N/mm² (MPa). This is the stress at which the bolt breaks.
• The second number ÷ 10 gives the ratio of yield strength to tensile strength. Yield is the point at which the bolt starts to stretch permanently.

Example, class 8.8: tensile strength 8 × 100 = 800 MPa. Yield = 800 × 0.8 = 640 MPa. In practice you can multiply the two numbers and then by 10 to get yield: 8 × 8 × 10 = 640.

Common grades at a glance

Nominal values are shown. Actual minimum values in the standard vary slightly with size, for example class 8.8 above M16.

How to spot the grade

• Hex bolts of class 8.8 and above must be marked with the class on the head, usually with the maker's mark.
• Unmarked bolts are usually class 4.6 or lower. Do not assume an unmarked bolt is high tensile.
• Socket head cap screws are commonly 12.9 and are marked on the head or the side.

Match the nut and washer to the bolt

A strong bolt is only as good as its nut. Under ISO 898-2 (IS 1367 Part 6) the nut class should be equal to or higher than the first number of the bolt class:

• Class 4.6 bolt: class 4 or 5 nut.
• Class 8.8 bolt: class 8 nut.
• Class 10.9 bolt: class 10 nut.
• Class 12.9 bolt: class 12 nut.

Use hardened washers under high-tensile nuts and bolt heads so that the bearing surface does not dig in and lose preload.

Stainless steel grades are different

Stainless bolts use a letter-and-number code under ISO 3506. A2 is equivalent to SS304 and A4 to SS316. The number after the dash is one tenth of the tensile strength, so A2-70 means A2 stainless with 700 MPa tensile strength. A2-70 and A4-70 bolts have a minimum yield strength of about 450 MPa, well below class 8.8, so do not substitute them for high-tensile steel bolts in a structural design without checking.

Structural (HSFG) bolts

High strength friction grip bolts to IS 3757, marked 8.8S or 10.9S, are made for pre-loaded structural steel connections. They come as a matched set of bolt, heavy nut and hardened washers and must be tightened by a controlled method. Use them only where the steel design calls for them.

Practical buying tips

• Do not mix grades in one joint. The joint behaves like its weakest bolt.
• Higher is not always better. Very high grades (10.9, 12.9) are less ductile, and when they are electroplated there is a risk of hydrogen embrittlement. Specify plating carefully or choose hot-dip galvanised 8.8 for outdoor structures.
• Give full details when ordering: diameter, length, thread pitch if not standard, grade, finish and whether you need a full or partial thread.

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.