Flashing Cement Market : Development Trends, Key Manufacturers and Competitive . Flashing cement is a specially formulated asbestos-free cement used for repairing leaks in shingles, metal or asphalt roofs, concrete, SBS or APP modified bitumen membranes flashings on walls, flues, chimneys, downspouts, skylight flashings, and cornices. Published 4 Years Ago by roshan k