Here in the GTA, bituminous roofing materials are just as welcome as they were back in the early days as they are now. But why are they still popular and where did they come from?
Bituminous roofing becomes popular
First introduced to the roofing industry prior to WWII, bitumens dominated the industry. The two types where coal tar pitch which is a by-product of the process of making coke, which is further processed into carbon steel and aluminum electrodes, and asphalt, a by-product created by the process of turning petroleum into gasoline.
Originally, flat roofs were made up of multiple layers of hot bitumen and a reinforcement layer of organic felt made up of paper, cotton fibres, and wood fibres.
The system was and still is a simple, durable, long-lasting roofing material still used today. Bitumen, however, are vulnerable to ultra-violet light so a layer of slag or gravel was imbedded into a flood layer of bitumen to protect the bitumen layer.
The process of applying 2 dry layers and 3 mopped layers to a wood roof structure continued until the 1950’s when a coated base felt was used to replace this multi-layer system.
In 1973-1974 an oil embargo existed which brought about the introduction of a 2-ply coated asphalt felt which reduced the number of mopping layers and required less labor. Unfortunately, these 2 ply layers were plagued with blistering. Today, roofing companies in Oakville and throughout the GTA use a 4, 5 or 6 layer material which has greatly reduced the risk of blistering.
Asphalt emulsions come into existence
Asphalt itself is water impervious. However, introducing an emulsifying agent such as bentonite clay it can be dispersed in water. This roofing system provides a stable base for reflective roof coatings and once cured, provides excellent fire resistance without the need for a gravel surface coating.
These emulsion based roof systems were so good, they were often used with a single-ply base sheet with several layers of emulsion and chopped fibreglass for reinforcement. This emulsion system was useful when resurfacing bituminous roofs and made an excellent base for reflective coatings.
Emulsion systems have one drawback in that they must be protected from freezing which makes them more difficult to use here in Canada with our low winter temperatures.
Many types of new roofing systems such as self-adhering modified bituminous membranes, aluminum roof coatings, and water based adhesives require an ambient temperature of at least 50 degrees F.
Emulsion systems are great in that they contain little or no VOC’s which aids in the creation of smog and contain no flammable solvents. They are also unaffected by high temperatures which make them ideal for use with modern reflective roof coatings.