What are Expanding Anchors?

Expansion anchors are a type of fastener designed for use in masonry base material that provides holding power through expansion. There are two kinds of expansion anchors: pre-expanded and unexpanded. 

Pre-expanded expansion anchors are inserted in a predrilled hole compressed and then exerts force to create the holding power. 

The unexpanded expansion anchor requires the anchor to be set after it is installed into the predrilled hole in the masonry.

Key Points

Some expansion anchors can be used only in solid concrete; others can be used in solid concrete, brick or block. The holding values of any expansion anchor are only as good as the quality and quantity of the base material into which it is placed. For example, if the base material is sandy and easily falls apart, then the holding values will be very low or non-existent.

It is essential that all Anchors are installed correctly in accordance with the manufacturer’s installation instructions. Basic points to remember are:

• Ensure suitability of anchor for the type of substance.
• Assess local factors e.g. proximity to the edge, reinforcement etc.
• Use a drill bit in good condition.
• Drill hole to correct diameter and depth.
• Clean out the hole thoroughly - especially critical for chemically bonded anchors.
• Ensure that the correct setting equipment and procedures are used.
• Tighten to correct torques recommended by manufacturers.

Direction of Loading

The most suitable Anchor for the application concerned can be selected after considering the direction of the applied load. The tension and shear values must be less than the safe working loads in the direction concerned. Other factors to be considered are centre to centre distances, centre to edge distances and proximity of reinforcement etc.

Tensile Loads

Common examples of Tensile Load situations include suspension of ductwork and pipework, mechanical services and suspended ceiling applications. These are loads which are applied along the axis of the fixing. 

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