Crow steps are a feature of buildings found in Scotland and elsewhere in the UK. A gable end of a roof made into steps with stone or bricks are called crow steps. Roofs in Scotland are typically steeper than in the rest of the UK (because it rains more) making for steeper and more step-like steps.
Crow steps are associated especially with castles, but are also found in baronial architecture and domestic architecture (houses) in Scotland into the 20th century.
Crow steps have one convenient aspect that may often be overlooked; they provide simple, if risky, access to the apex of the roof. In Scotland, chimneys are traditionally swept from above rather than below, so crow steps would once have been used for access by chimney sweeps. This would of course be illegal under current health and safety law.
Construction
With crow steps, the roofing slates (rarely tiles) do not reach the end of the building, so making for a special problem with keeping the roof watertight. Many different schemes are found for overcoming this, some of which are described below. Terms currently used in Scotland are highlighted.
- Slates may be laid to the edge of the crow step, with the last slate raised by a wedge (tilting fillet). Then mortar (lime mortar or cement) would be laid over the edge of the slate to seal the gap. Other solutions involve working with lead.
- A groove approximately 50 mm long is cut into the inside edge of the steps. Lead is inserted into this groove, called a raggle. The lead is laid over the end slate, which is raised by a tilting fillet.
- Lead is inserted into a raggle, and used to make a trough running down the inside edge of the steps. The far edge of the trough is raised over a triangular fillet. Slates are then laid resting on that trough edge and overlapping into the trough, which is open and runs directly down to gutters (roans).
- Rather than working a raggle, lead may be places into the gaps between bricks as they are laid.
When lead is to be held into a raggle, small pieces of folded lead called bats are inserted at intervals and hammered in so they expand. The raggle is then sealed with mortar.
Crow steps are frequently made of sandstone, even on buildings otherwise of granite, and it is said that the porous nature of sandstone leads to problems with water penetration. Because of this, crow steps are sometimes capped with lead or (as in the picture, unsuccessfully) sealed with other materials.
