GAF TECHNICAL POINT Home » How To Clean Roofing Shingles | Timberline/GAF Roof Cleaning Instructions » GAF TECHNICAL POINT GAF suggests the use of bleach in a detergent to rid the roof of black bacteria stains. Bleach, or sodium hypochlorite, is completely compatible with a roofing shingle. Leave a Reply Cancel replyYour email address will not be published. Required fields are marked *Name* Email* Website Save my name, email, and website in this browser for the next time I comment.