Through bolts are frequently used as mechanical anchoring solutions for heavy loads in cracked or non-cracked concrete. In our article, we take a look at the special features and functionality of through bolts, and offer valuable tips on how to install them correctly.
What is a through bolt?
A through bolt is a torque-controlled expansion anchor (frictionally engaged) for fastening metal and wooden attachments (medium heavy to heavy loads) to concrete. It meets high requirements towards load bearing capacity and safety. Through bolts are used for fastening heavy and safety-relevant attachments in both indoor and outdoor areas. These include, for example, brackets for signs and lighting, installing awnings, support legs, stairs and railings but also wiring systems, ventilation stacks and cable ducts and, last but not least, anchoring substructures for facades. For outdoor areas, through bolts made of A4 stainless steel or HCR 1. stainless steel are well-suited as they account for special requirements such as highly corrosive environments. But how do through bolts work and what mistakes should you avoid during installation?
How do through bolts work?
Through bolts work by driving a steel bolt into the Base material. The correct setting depth can be easily determined by the black marking on the anchor. When installed, this marking must be flush with the concrete surface. When the nut is tightened, a metal shield expands, which in turn clamps the bolt into the substrate. Depending on the respective assessment (ETA), through bolts are suitable for anchoring in cracked and non-cracked concrete.
Caution on edges
Due to the expansion forces, the through bolt as a fastening element does have its limits in some applications. This is mainly the case when the fixing points are close to the edge of concrete surfaces. If the concrete does not have enough mass to absorb the expansion forces, the result may be splitting of the substrate material and in the end even complete failure of the fixing point.
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