8 min read

December 11, 2020

BS 8539 for M&E anchors: selecting and installing fixings

BS 8539 is the British code of practice for selecting, supplying, installing and testing post-installed anchors in concrete and masonry. For M&E (mechanical and electrical) contractors, these are the anchors that connect the structure to supports for pipework, ductwork, cable containment such as tray, basket or trunking, and plant. They can also secure the brackets and channel frames that carry those services, including overhead. If an anchor does not suit the substrate or is installed with the wrong tool or method, the support assembly may not carry its design load and can collapse.

The current edition is BS 8539:2012+A1:2021. BSI withdrew BS 8539:2012 on 17 March 2021. This guide does not replace the standard or the project design.

What BS 8539 covers

The standard gives guidance on the selection, supply, installation and testing of post-installed anchors fitted into drilled holes in concrete or masonry. Its audience includes the designer, specifier, contractor, installer, site tester, manufacturer and supplier. Each has a part in getting the specified anchor to site, installed as intended, and checked where the project calls for it.

In our experience, anchor selection on M&E projects can be left until late in the job, then passed to a buyer or installer who picks a familiar product. Whoever selects the anchor takes on the specifier’s role for that decision. Selection needs the design and site information, not just a part number that has worked somewhere else.

For examples of M&E support systems, see the MIDFIX MX Channel system and MX-R rooftop plant support frames. Where an anchor connects a service support to concrete or masonry, it still needs to be selected for the actual substrate and load.

The anchor is usually the weakest link in a bracket. In our experience, there have been few true anchor failures, but plenty of brackets and assemblies collapse. A collapse can follow when the anchor was unsuitable for the application or was not installed as its manufacturer instructed.

Who does what?

The designer supplies the load and substrate information. The specifier uses it to select and identify the anchor. The manufacturer provides product performance and installation information; the supplier sends the specified anchor and the tools it needs. The contractor arranges installation, training and supervision. The installer follows the manufacturer’s instructions and raises problems on site. A competent tester carries out any test the project requires and records the result. One person may hold more than one role, but the selection decision still needs an owner. For a role-by-role view, read who is responsible at each stage of anchor supply and installation.

Six checks before selecting an anchor

Six checks cover substrate, loads, environment, type of installation, working principle and required approval. Work through them before ordering. If the substrate strength is unknown, establish it with an allowable load test before selecting the anchor. Read the supporting guide to anchor selection checks for M&E supports for more detail on those checks.

1. Substrate. Identify what the anchor will be fixed into. For concrete, establish whether it is cracked or non-cracked. If there has been no assessment to show otherwise, assume cracked concrete. For brick and block, identify whether the material is solid, hollow or another type. An anchor approved for one substrate may not suit another. For overhead services supported from concrete ceilings, the ETA needs to cover cracked concrete.

2. Loads. Confirm the load the anchor will carry over its working life. Check the load’s magnitude, direction and duration, and whether it is static or dynamic. For a bracket carrying pipework or cable containment, the supported services contribute to the load on the anchors. The designer’s requirements need to be checked against the performance information for the exact anchor and application. MIDFIX’s fixings and anchors category is a product range, not a substitute for that check.

3. Environment. Check whether the fixing is indoors, outdoors, near the coast, in humid conditions or in a special environment. The finish must suit the exposure. In chlorinated swimming pool environments, chlorine can affect some grades of stainless steel and lead to stress corrosion cracking.

4. Type of installation. Decide whether the anchor is a flush fix, fitted into the substrate before the fixture, or a through-fix, fitted through the fixture and into the substrate. The installation arrangement affects which anchor is suitable and how accurately it can be positioned.

5. Working principle. Anchors transfer load through friction, interlock or bonding. Throughbolts and drop-in anchors expand against the hole; concrete screws key into the substrate; resin anchors bond to it. Expansion anchors place more stress on the substrate, so check the product information for edge distances and spacing. A drop-in anchor that expands against a brick, for example, can damage it.

6. Approval and evidence. Check what approval the project needs and whether an ETA covers the anchor’s intended use, substrate and installation. The ETA and manufacturer’s documents identify the product and give its performance and installation information. An ETA for one application does not make the same anchor suitable for every base material or condition.

What an ETA tells you

ETA means European Technical Assessment. It gives assessed performance information for a specific anchor and intended use. Check the product name, manufacturer reference, assessment number, substrate and installation conditions against the job. Use the associated installation instructions too; the performance data only applies when the product is used within the assessed conditions.

Where an ETA-assessed anchor is available for the application, our advice is to use it. The assessment helps the specifier compare products and check whether the proposed anchor has evidence for the substrate and load. It does not replace the selection decision. The design still has to match the actual load, base material, anchor position and installation arrangement. MIDFIX’s ETA anchors category shows part of the product range. For a closer look at what the assessment does and does not tell you, read what an ETA tells you about a specific anchor.

Supply, substitutions and “breaking spec”

The anchor specified should be the anchor delivered to site. We often see a familiar problem: selection happens late, then commercial or supply pressures mean a different box arrives. A similar size or appearance does not make it the same anchor. Manufacturer references, performance, approvals and installation instructions can all differ.

If the specified product is unavailable, do not pass the substitute straight to the installer. Tell the original specifier and follow the change management procedure in the standard. Repeat the selection checks against the substrate, load, environment, installation method and approval. Confirm the replacement and its installation instructions before work starts. Whoever chooses the alternative is now making the specifier’s decision for that product.

The supplier’s part is to provide the specified anchor and make the required accessories available. That can include the correct drill bit, hole-cleaning equipment, setting tool or torque wrench. The supplier should also provide or arrange installation training and raise a proposed alternative before it is treated as an approved change. Read what must arrive on site with the specified anchor for the supply handover. If a replacement is proposed, follow what to do before changing a specified anchor.

Installation and training

Every anchor has its own installation instructions. Training on one product does not mean an installer knows how to fit another, even if the anchors look alike. The installer needs the product instructions, the specified drill and setting tools, and practical knowledge of the anchor being used. The contractor should arrange suitable training and supervision, including for the supervisor who checks the work.

We have seen what can go wrong. A drop-in anchor can be left under-set if the installer does not use the correct setting tool or drive the plug to the correct depth. Under load, it may carry only part of the intended load and the bracket can collapse. A resin anchor may fail to develop the required bond if the hole has not been cleaned. A throughbolt installed without the specified torque wrench may be under- or over-tightened. Read how to set a drop-in anchor with the correct tools.

The small details matter. Drill the hole to the specified diameter and depth. A worn drill bit can leave an undersized hole, making installation difficult and increasing stress in the anchor. Clear dust as instructed; compacted dust at the bottom of a hole can stop an anchor seating properly. Use the setting tool made for that anchor, not one that happens to fit.

Training needs to cover the anchor being installed, not just anchors in general. Read what anchor installer training should cover for more on the course content. MIDFIX Academy lists anchor training courses.

Stop and ask the supervisor or specifier what to do if you strike reinforcement or a tension bar, find an unknown base material, do not have the drill dimensions or tools, or are asked to install an anchor that differs from the specification. Our advice to installers is to stop and ask at those points. Do not decide on a new position or product at the workface. See when an anchor installer should stop and ask for help. Supervisors can also read how to check an anchor installation against its instructions.

Where anchor installations go wrong

In our experience, the two recurring causes are poor selection and installation error. The risks are easy to picture: an under-set drop-in, a resin hole left dirty, or a throughbolt tightened without the specified wrench. The anchor can be a sound product and still fail to do its job if the substrate, load or installation does not match its assessment and instructions.

A bracket can also be asked to carry more after it has been installed. This is known as “piggybacking” or parasitic loading: another service or support is added to the bracket, increasing the load on the assembly and anchors. For example, extra pipework or cable containment may be added to a bracket originally signed off for another arrangement. That change needs a new load calculation before the extra service is hung. Read lessons from past anchor failures for more on selection and installation risks.

Testing and records

We distinguish two different purposes for site testing. An allowable load test helps establish what an anchor can carry where the substrate strength or application data is not available. A proof test checks the quality of an installed anchor. One test does not answer the other question. Read proof testing and allowable load testing explained for more on the distinction.

Before a proof test, the tester needs to know how the anchor was installed, which drill bit and setting tool were used, whether a torque wrench was used, the substrate, and the load required by the engineer. The proposed test load also needs to be checked against the manufacturer’s recommended load. Agree the test method and requirement before the tester starts, and use a competent tester following the relevant CFA guidance.

A proof test is not required where an ETA anchor has relevant data for the substrate and has been installed and supervised by competent people. A project may still specify testing. Set the test requirement against the current standard, product assessment and project design before work begins.

Keep the product reference and delivery record, installation instructions, any approved change, and the supervisor’s check together. If testing is specified, retain the request and report with them. Records should make it possible to identify what was specified, what arrived and what was installed.

A short project checklist

Before ordering

Plan anchor decisions early on an M&E project, identifying the substrate and its condition, the load, environment and installation arrangement.
Select an anchor with product evidence for that application. Record the manufacturer and exact product reference.
Coordinate anchor supply and installation for M&E contractors: give the supplier the specification and make sure the required instructions, drill bit, cleaning equipment and setting tool can reach site with the anchor.
Agree who handles substitutions, training, supervision and any site testing.

Before and during installation

Check the delivered product against the specified reference.
Give the installer the current manufacturer’s instructions and the correct tools.
Check the hole diameter and depth, cleaning and setting method against those instructions.
Stop and ask when the substrate, product or site conditions differ from the information provided.
Record the anchor used and the supervisor’s check. Record any approved change.

At handover

Keep the specification, delivery and installation records together.
Add the test request and report if the project calls for a test.
Record any change to the services or support arrangement that affects the load on the anchors.

The article on practical trade-offs of anchor compliance considers the planning and coordination involved. If you need to discuss an M&E anchor application with MIDFIX, contact the team.

Common questions

Can I replace the specified anchor with one that looks the same?

No. Similar appearance does not show that the performance, approval or installation method is the same. Tell the original specifier and follow the change management procedure before the replacement is installed.

Does an ETA mean an anchor will work in any concrete or masonry?

No. Check that the ETA covers the specific product, intended use, substrate and installation conditions. The selected anchor still has to suit the project’s load and design.

Does every installation need a proof test?

Not necessarily. A proof test is not required when an ETA covers the substrate and the anchor is installed and supervised by competent people. Follow the test requirements in the current standard and project specification.

Why train an experienced installer?

Different anchors need different hole preparation, drill sizes, setting tools and installation steps. Training helps the installer follow the instructions for the actual product on the job and know when to stop and ask for advice.

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