A concealed anchor (also called a blind anchor) is a metal fastening device that is built into masonry or concrete during construction to provide a hidden connection point between a wall and an adjoining structural element, without any part of the anchor being visible on the finished face.
Application
Why concealed anchors are used
In many construction situations a strong mechanical connection is needed between two components — for example between an inner leaf and an outer leaf of a cavity wall, between a masonry wall and a steel frame, or between a facade and a load-bearing structure. Exposed bolts or brackets would spoil the appearance of fair-face brickwork, natural stone, or rendered surfaces. A concealed anchor solves this by being completely embedded within the wall during the bricklaying or concrete-pouring process.
Types and forms
Concealed anchors come in several designs depending on the load they must carry and the materials involved:
- Flat-bar anchors — thin stainless-steel strips bent into an L or Z shape, laid into a mortar bed joint so they bridge between two leaves of masonry.
- Dovetail anchors — a slotted channel is cast into concrete and a dovetail-shaped metal clip slides into the channel, with the other end embedded in the masonry course.
- Threaded stud anchors — a bolt is cast into a structural element with only the threaded end protruding into the cavity, where it is later connected to the adjacent wall layer.
- Expansion-type blind anchors — inserted into a pre-drilled hole and expanded mechanically or chemically so that no part remains visible once the adjacent finish is applied.
Key considerations
- Material should be stainless steel or hot-dip galvanised steel to prevent corrosion inside the wall.
- Spacing and load capacity must comply with structural engineering calculations and applicable building codes.
- Correct placement during construction is critical because concealed anchors cannot easily be repositioned once the masonry is laid.
Related terms
- Wall tie
- Cavity wall
- Mechanical anchor
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