CHAPTER 35 — Roofing in Early Canadian Mills, Foundries & Industrial Workshops (1700s–1900s)

Mills, foundries, blacksmith shops, and early industrial workshops powered Canada’s economic development during the 18th and 19th centuries. These structures required roofing systems designed to handle intense heat, heavy machinery vibration, fire risk, and large interior workspaces. Their roofs reflect the earliest stages of Canada’s industrial evolution.

Why Industrial Roofing Was Unique

• Fire hazards: Sparks, furnaces, and kilns demanded non-flammable materials.
• Large interior spans: Workshops needed open spaces for mills, looms, and metalworking.
• Moisture & heat: Steam-powered equipment created unique environmental challenges.
• Constant vibration: Machinery stressed roof fasteners and framing.

Common Roofing Materials in Early Mills & Workshops

1. Corrugated Iron & Steel

The dominant roofing material for mills and foundries, corrugated sheets offered strength, vibration resistance, and fire protection. They also allowed rapid construction of wide roof spans.

2. Wood Shingle Roofing

Used in early water-powered sawmills and gristmills before industrial metal roofing became widespread. These roofs required frequent replacement due to heat and moisture exposure.

3. Slate Roofing

Slate was used on high-value mill buildings and urban industrial workshops because of its fireproof nature and durability.

4. Early Built-Up (Tar & Gravel) Roofing

Flat or low-slope mills used tar-and-felt built-up roofs to handle heat and provide waterproofing over large, rectangular structures.

Roof Designs in Industrial Architecture

• Gable roofs for early wooden mills.
• Sawtooth roofs providing natural light for factories and machine shops.
• Monitor roofs with clerestory windows for ventilation and lighting.
• Low-slope metal roofs for large industrial complexes.

Environmental Challenges

Industrial buildings faced:

• Steam condensation that damaged poorly ventilated roofs.
• Heavy structural loads from machinery and snow.
• Thermal expansion from furnace heat or direct metal contact.
• Fire outbreaks common in foundries and workshops.

Historical Significance

The roofs of mills and foundries played a crucial role in Canada’s industrial rise — from Maritime shipyards to Ontario factories to Prairie grain mills. Many heritage industrial buildings still feature original roofing systems that reflect Canada’s early craftsmanship and engineering.

This chapter is part of the ROOFNOW™ Canadian Roofing History Archive.