When History Cracks: A Closer Look at Pencheck Stair Failures

We were recently instructed to inspect a collapsed section of a historic communal staircase in a tenement building in Edinburgh. The staircase, over 150 years old, is a helical “pencheck” stair — a clever structural form where each cast stone tread interlocks with those above and below, transferring load and torsion into the supporting wall.

Two treads between ground and first floor had failed and fallen onto the flight below, prompting a dangerous building notice. Our inspection was limited due to access restrictions but revealed:

• Likely accidental damage, such as impact from a dropped object, was the most probable cause of failure.

• A third tread showed signs of cracking.

• Water ingress may have contributed, especially through freeze-thaw action in existing cracks.

• Crucially, enough of the damaged treads remained embedded in the wall to preserve some structural integrity.

This type of stair, while appearing to cantilever, relies on a delicate balance of compression, interlocking geometry, and robust wall support. Care must be taken during repair to avoid destabilising the structure.

We recommended resin-based repairs, stainless steel crack stitching, and a full follow-up inspection once initial stabilisation works are complete.

Pencheck stairs are beautiful but unforgiving — they reward care, precision, and a deep understanding of historic construction methods. At DRM, we’re proud to help preserve them for future generations.