During the last two decades of the 19th century an important new kind of roofing product began to emerge, where previously roof coverings were mostly wooden shingles, slate and metal roofs.
This was wool felt impregnated with bituminous material, such as tar and asphaltic bitumen, which was produced in roll form. This mineral felt was developed and modified during the 20th century becoming the predominant roofing form throughout the US.
Asphalt-impregnated Felt Roofing
Asphalt-impregnated felt was first sold as a roll roofing material, either with a smooth surface, which was often mica-covered, or with a granular or mineral-faced surface composed of crushed slate or granite pressed into the asphalt, to prevent the material sticking together whilst in roll form, and to protect it from the environment.
History of Felt Roofing
Around 1900, the mineral-faced form of asphalt-impregnated felt began to be supplied as roofing shingles cut into individual rectangles at first, then after about 1915, as strips with notches that stimulated the butts of two or three individual shingles. This form is still around today with little change except for a wider variety of colours and butt designs in the felts.
Mineral Felt Roofing
The mineral felt could be installed in a number of ways, such as: mechanical fasteners, hot asphalt, cold asphalt adhesive, non-asphaltic adhesives, heat (torch or hot air) or a combination of these.
Lastly, there is often a layer of solar-reflective stones spread over the surface of the mineral felt. The presence of these stones protects the felt surface from the damaging effects of the sun’s rays.