Natural slate can vary in color and weathering. GAF distinguishes cosmetic changes from pieces that do not seat correctly and should not be installed.
GAF technical bulletin: Color and shape variations with slate roofs.
What this means for your roof
Natural slate can vary in color and weathering. GAF distinguishes cosmetic changes from pieces that do not seat correctly and should not be installed.
A useful question for your contractor
Ask how unsuitable slates are identified and how batches are blended for appearance.
Ask for the answer to be tied to the actual roof condition and the exact product being installed. Keep the agreed repair or installation detail with your estimate and project photos.
Bulletin revision: February 1, 2021. This is the date of the manufacturer source, not a claim that this website guide existed on that date.
Read GAF: Color and shape variations with slate roofs
This homeowner summary explains the cited bulletin. The complete manufacturer document and current product instructions govern the installation details. A requirement for one manufacturer or product should not be transferred to another without checking.