Anchor selection – BS 8539 Guidance
In our latest sound-out episode Steve talks through the key questions around BS 8539 guidance and anchor selection. If you are looking for a comprehensive guide to BS 8539 then click here.
How do we select an anchor in accordance with BS 8539?
Well, it is a good question because selection particularly within M&E building services tends to be a bit of a problem, what usually happens is the actual selection process is left til the end and it is the installer that has the responsibility to select the anchor and what they tend to do is usually default to an anchor they usually use to do the install with.
What steps should we follow for anchor selection in relation to the BS 8539?
There has got to be due diligence when it comes to anchor selection, it is important we choose the correct anchor for the specific installation. We need to look at the following factors;
- Environment (internal/external)
- Type of installation (through fix or is it a flush fix)
- Working principles of the anchors
- Accreditation required
What type of substrate will the anchor be fixing onto?
What type of substrate are we fixing into, is it cracked concrete, non-cracked, is it hollow is it solid?
How does BS 8539 define cracked or non-cracked concrete?
Concrete is likely to be cracked from a variety of causes including permanent actions and characteristic variable actions, thermal movements, shrinkage and the restraint of deformation. Anchors qualified for use in cracked concrete are expected to function reliably in the expected widths of cracks developed as a result of tenisle stresses in concrete structures designed in accordance with BS EN 1992. In the region of an anchor, the concrete might be cracked or non-cracked.
Anchors should be chosen that are suitable for use in cracked or non-cracked concrete, as appropriate. The specifier should assume the concrete to be cracked unless an exercise has been carried out to determine whether it is cracked or non-cracked.
What do we need to know about an anchor load?
We need to look at the loads: that the anchor is going to be subjected to throughout its working life.
What type of environment surrounds the anchor?
We need to look at the environment it is working under, is it external or internal and is it under any special conditions such as swimming pools as this will often determine the specific finish of an anchor.
What type of installation is appropriate for a given substrate?
We need to understand; is it through fix or a flush fix.
Understanding the working principles of the specified anchor
The actual working principles of the anchor is an extremely important factor to consider when we are selecting an anchor. Certain anchors pose a large amount of stress on the substrate. For example a deformation controlled anchor commonly known as a ‘drop-in anchor’ you would not use on brickwork as it would damage the brick. We need to look at an anchor that is kinder to the substrate. For concrete, a preferred anchor could be a concrete screw or a resin anchor.
What type of accreditation is required?
And the final bit we need to look at is the accreditation required for that install, so what do we need? ETAs, RAS approvals? It all depends on the accreditation required.
To summarise, if we look at those 6 points it is not fair or correct to leave it to the last minute for the installer to make the final decision.
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If you are looking for further resources such as toolbox talks then head over to the Construction Fixing Association website (CFA)
Whichever stakeholder you are within an anchor/fixing supply chain, it is important that you select the right anchor going over the due diligence as outlined in BS 8539. As we know many drop-in anchors fail due to installation failure. If you are a contractor, site supervisor or an anchor installer and would like to ensure all anchors are installed on-site to the highest standards then find out about the MIDFIX Academy.Learn more about the MIDFIX Academy
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