Why would shingles fall off the roof?

Shingles fall off the roof for several interrelated reasons, most involving wind, age, and installation quality. The most common cause is wind damage breaking the sealant bond. Asphalt shingles have a factory-applied thermally activated adhesive strip that bonds each shingle to the one below for wind resistance. High winds, especially if shingles were installed in cold weather and never properly sealed, can break this bond and peel shingles off. As shingles age past 15 to 20 years, this adhesive weakens, granule loss makes shingles lighter, and the mat becomes brittle, so even moderate winds can cause blow-off. Improper installation is a major cause of early failure, including high nailing where nails are placed above the manufacturer nailing line, using too few nails per shingle, overdriven nails that cut the fiberglass mat, or under-driven nails that prevent shingles from lying flat and sealing. Poor attic ventilation causes excessive heat buildup that weakens sealant and warps shingles, making them vulnerable. Installing new shingles over an existing layer during a layover prevents proper sealing over the uneven surface. Physical damage from falling branches, ice dams, or foot traffic can also dislodge shingles. If shingles keep falling off repeatedly, it usually indicates the roof is at end of life or has systemic installation defects and needs replacement rather than spot repairs.