Excess Roofing Granules on Shingles

Technical Bulletin #18

Current as of May 2019

During the roofing manufacturing process, roofing granules are applied into the hot top coating asphalt. An excessive amount of granules is used to provide total and complete coverage of the asphalt. The asphalt must be covered to ensure protection from solar ultraviolet radiation.

The granules are "pressed" or embedded into the asphalt coating while it is still hot. Some of the excess granules may not be firmly embedded but are only loosely held in place on the roofing sheet. The roofing machine is designed to reclaim the excess "hitchhiker" granules and re-use them. However, some of the "hitchhiker" granules are packaged with the shingles in the finished bundle.

During the first two years of shingle exposure on the roof, the "hitchhiker" granules will come off the shingles and may be found in the gutters or at the bottom of downspouts. Loss of these excess "hitchhiker" granules is completely normal and in no way results in a reduction of the weatherproofing life of the shingles. Granule loss only becomes a concern for shingle performance when bare spots of coating asphalt are exposed on the surface of the shingles.

The information contained in this bulletin is for general education and is not intended to replace advice from a qualified contractor or direction on usage/installation from the manufacturer. Consumers should be aware of the safety hazards associated with work on roofs and, before doing so themselves, should consider following CASMA s advice of using qualified contractors. This bulletin may be reproduced with permission on condition that it be reproduced in whole, unedited, with attribution of copyright to CASMA.