The loss of the mineral finishing (slates or granules) of a bituminous roofing membrane is determined by a specific test EN 12039. This test is part of the product standard EN 13707 “flexible bitumen membranes for roofing application”.
The principle of this test determines the adhesion of the mineral finishing in a brush test under specific circumstances. The weight of the slates or granules recovered after the test is compared with the original weight of the slates or granules.
The requirements of this standard define a maximum limit of 30% after the brush test. In practice, there are always loose slates or granules on a freshly manufactured membrane, and these come loose in the initial period after installation due to the various actions performed on the roofing membranes (movement, installation, transport, etc.).
To maintain a roof during normal standard roof maintenance, especially in the first few years, is very important for this purpose.