Corner Masonry Widths: When Is a Wind Post or Structural Post Needed?

External corners in masonry construction provide mutual restraint — each wall helps to stabilise the perpendicular wall. But this restraint works only if there is a sufficient length of masonry on each side of the corner. Very short corner returns — where a large window or door opening sits close to the corner — may leave an inadequate masonry section that cannot provide the necessary lateral stability.

The Guideline Dimension

As a general rule, keep a minimum of 665 mm of solid masonry on each side of an external corner.

This dimension comes from the slenderness rules in Part A of the Building Regulations. A masonry pier of 665 mm or more provides a stiff enough buttress to give the adjacent wall adequate lateral support against wind loads.

What 665 mm Represents in Practice

In brick construction, 665 mm is approximately 2.5 brick lengths (at 215 mm per brick + 10 mm joint). For blockwork (440 mm blocks), it is approximately 1.5 block lengths. The requirement is often achievable with careful window placement — but can become an issue on modern designs that push large glazed openings close to building corners.

What Happens Below 665 mm?

When the masonry corner return is less than 665 mm — for example, because a large window is positioned very close to the corner — the wall may not have adequate lateral stiffness simply from the masonry alone. In this case:

– A structural post (steel SHS or UC column) may be specified at the corner, built into the cavity or sitting internally against the corner masonry
– The post provides the necessary lateral stiffness that the insufficient masonry cannot

This adds cost and complexity but is structurally straightforward.

Raise a Change Request

If your architectural drawings show an opening close to a corner that results in a return of less than 665 mm, raise a Change Request with PorthouseDean before the drawings are finalised. We will check whether the corner dimension is acceptable given the full geometry of the surrounding structure, or whether a column is required.

This is much easier to resolve at the design stage than after construction has begun.

Contact us or raise a Change Request to have your corner masonry widths reviewed.