We're naive about construction and roofing, so mostly learn through negative experiences. Not this time. After other people patched our leaky tar and gravel roof ineffectively, making us think we needed a whole new roof, Northway came out, said our roof was basically fine still. He explained that our attempts to preserve our roof were actually counter-productive -- that artificial white sand actually protects the tar from the sun, and every time we shoveled snow we removed some of the sand. He did a much broader tar patch than the last guys -- no leaks for three years and counting, and no new roof for another few years at least!