Impact to roof integrity due to loss of gravel on shingles
I have a portion of my roof around the dormers where due to working on the dormers the gravel on the shingles is badly worn off. What is the role of the gravel? I would like to know what is the impact to the roof in terms of "water tightness" and will the loss of much of the gravel severly impact the "normal" life of the roof?
The granules are there to protect the mat. Once the granules are gone, the felt deteriorates very quickly, starts to absorb water, which then causes the mat to swell which in turn sets up unequal expansion/contraction and leads to cracking. If you're in an area where freezing/thawing occurs then the process is accelerated even further. As a rule, once the mat becomes exposed, it would be prudent to replace the roof (or at least the shingles).