13 – December 1971
Let’s be realistic about roofing gravel.
Accept the fact that due to the small proportion of total production of the gravel industry consumed by roofing contractors, the roofing industry is in a weak position to demand what it may consider to be the ideal.
The following are important functions of a good roofing aggregate:
- to protect the bitumen form the ultra-violet rays of the sun which cause deterioration
- to provide a protective weathering or light traffic surface over the bitumen
- to help hold a sufficient top pour of bitumen in place
- to cut down hear absorption. Since light coloured material absorbs much less heat from the sun’s rays than dark material, the use of light coloured gravel will cut down the heat absorption, and subsequent transmission of heat to the building’s interior.
A generally available, acceptable gravel:
- is sized approximately 1/4″ to 3/4″ to provide reasonable embedment and an interlocking opaque surface.
- is composed of non-porous particles so as to prevent water absorption and resulting frost action deterioration.
- is reasonably free from dust, moisture, ice and snow. All gravel contains a certain amount of dust and the moisture quantity will vary with differences in local conditions.
- by its opaqueness will prevent ultra-violet light from attacking the bitumen.
- is either crushed or round – is crushed it should be reasonable free from long splinters.