Avoid Dangerous Errors When Installing AS5216 Concrete Anchors

Concrete screw anchors are a fast, efficient, and reliable solution for securing building services, seismic bracing, and ceilings to concrete structures. However, installation errors can significantly compromise their structural integrity, leading to failures that could have been avoided.

Choosing the Right Concrete Screw Anchor

Not all anchors are created equal. To ensure compliance with AS1170.4 and AS5216, the anchors you use must be preapproved for cracked concrete under C1 & C2 seismic conditions. The required seismic preapproval level depends on the building importance level outlined in the NCC (National Construction Code).

Uncertain about compliance? KUSCH can specify and certify the right anchors for your project based on design loading and seismic requirements.

Common Installation Mistakes & How to Avoid Them

Over the years, we’ve been asked to investigate the cause of occasional concrete anchor failures, and the findings typically reveal installation errors—not product defects. That’s why we worked with Iccons to create a short video highlighting important considerations when installing seismic screw anchors—one of the most common fixings used to connect building services, ceilings, and partitions to a concrete structure.

🚨 A key risk installers must understand: Overdriving screw anchors will significantly reduce their load capacity, and this reduction may not be immediately obvious.

From the moment the anchor head contacts the concrete surface, any further rotation of the screw can cause the threads to strip the surrounding concrete, rapidly reducing its pull-out capacity. As seen in the video, just two seconds too long on the trigger of an impact driver can cause the anchor to freely rotate by hand, indicating zero load capacity.

The issue of stripped holes also arises when drilled-hole depths are insufficient. If the depth is too short, installers may continue driving an anchor to close the gap between the bolt head and the concrete surface, only to find resistance when the anchor reaches the base of the hole. If the depth is notably insufficient, the error is obvious. However, if the anchor contacts the base just before the head is fully seated, it’s common for installers to overdrive the screw anchor, inadvertently stripping the concrete thread in the process.

Best Practices for Installing Screw Anchors

❌ Overdriving the anchor – Driving the anchor in too far prevents it from gripping the concrete effectively.
✅ Solution: If you overdrive it, redrill a new hole 80mm away and install the anchor properly.

❌ Incorrect hole depth and size – Drilling a hole that’s too shallow or too wide reduces the anchor’s holding strength.
✅ Solution: Always follow the manufacturer’s recommended depth and diameter.

❌ Stripping the concrete – If the anchor spins freely after installation, it has likely stripped the concrete, making it ineffective.
✅ Solution: If an anchor doesn’t fully seat immediately, the hole depth is likely incorrect. If the head rotates after contact with the slab, it’s being overdriven. The safest solution is to drill a fresh hole 80mm away and start again.

Engineers Rely on Proper Installation for Load Capacity

Screw anchors provide considerable load capacity when correctly installed, but incorrect hole depths and overdriving will rapidly compromise their strength. The great advantage of these fixings is their rapid installation time, and taking care during installation ensures they achieve their full design capacity.

Watch the Video to See These Techniques in Action

Proper anchor installation is critical for safety, compliance, and structural reliability. Watch our video with Iccons to see the correct techniques in action and learn how to avoid common mistakes that can lead to failures.

Need expert advice on seismic-rated anchoring solutions? Get in touch—we’re happy to help!