A Crow-stepped gable is a stair-step type of design at the top of the triangular gable-end of a building. The top of the parapet wall projects above the roofline and the top of the brick or stone wall is stacked in a step pattern above the roof as a decoration and as a convenient way to finish the brick courses.
Early examples, from the 15th century onward, are found in England, Denmark, Germany, Switzerland, and Sweden. Crow-stepped gables were also used in Scotland as early as the 16th century. Examples of Scottish crow-stepped gable can be seen at Muchalls Castle, Monboddo House and the Stonehaven Tolbooth, all late 16th and early 17th century buildings. Crow-stepped gables are also common on Danish medieval churches.
In the Dutch language, this design is termed trapgevel or "stair-step gable", characteristic of many brick buildings in the Netherlands, Belgium and in Dutch colonial settlements. 19th century examples are found in North America, and the step gable is also a feature of the northern-renaissance revival styles.
Convenient access to the roof ridge motivated the crow-step design, along with the availability of squarish stones to accomplish this form of construction. The access would have been convenient for chimney sweeps and roofers in earlier times, where cranes were non-existent and tall ladders were not common.
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 italicised.
When lead is to be held into a raggle, small folded lead wedges 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.
The Nuttall Encyclopedia suggests this architectural feature is called Corble steps. However, since it does not give the much more widespread name corbie steps (from the Scots language corbie: crow) it is likely that this was based on a misreading of lower case "i" as lower case "l". Another term sometimes used is craw step.