What is involved in Heritage Rehabilitation
How heritage standards are maintained
As Historic City Hall is a National, Provincial and Municipal Heritage Resource, all rehabilitation of the building must meet national standards for the treatment of such properties. For any restoration work on the building, statutory approvals must be secured from both the Provincial and Municipal Heritage Approving Authorities, in accordance with the Alberta Historical Resources Act, to ensure compliance with these standards.
Scarcity of materials, methods and trades
Rehabilitation of historic buildings differs greatly from new construction. The materials, methods and trades required for historical rehabilitation projects are scarce and costly. For instance, the art of stonemasonry began to die out in the mid-1900s when construction began to favour concrete and brick. The refurbishment of historic wood, terracotta and other vital heritage materials also require specialized skills and training.
The restoration of a 100-year old building, intended to last for over another 100 years, requires proportionately more time to plan than new construction projects. Thorough research is carried out on the historic materials that will be used in the rehabilitation.
For instance, the replacement sandstone must be physically and visually compatible with the existing stone and have appropriate density to last for a century. The mortar used to secure the sandstone must be structurally and visually matched to the sandstone. Detailed specifications are required to procure each heritage material and plans are made for custom construction in some areas. For example, new windows cannot be purchased off the shelf. They must be custom made to match the originals as much as possible in both materials and appearance. Such intricate specifications and plans are required for every component of Historic City Hall’s renewal.
Why sandstone and not something more widely available?
The national standards require that any historic materials must be replaced “in-kind”. Calgary was historically known as “Sandstone City” and the original sandstone is essential to the heritage value of Historic City Hall. In addition to this component of its heritage value, an alternate material such as limestone may be chemically incompatible with the sandstone which could cause deterioration of the latter.
Initially, the sandstone used in the rehabilitation will look a bit different from the original sandstone as it will take a number of years to weather. In time, both the original sandstone and that used in the rehabilitation will blend seamlessly.