The finished shingles are what homeowners see, but performance depends on the layers and details beneath them. Owens Corning and other major manufacturers treat roofing as a coordinated system of shingles, underlayment, water-protection components, starter materials, ridge components and ventilation. That is the right way to think about replacement planning.
Roof deck. After tear-off, the exposed decking can be checked for damaged, deteriorated or unsuitable areas. Hidden wood problems cannot always be fully confirmed before removal, which is why the estimate should explain how decking repairs are handled if they are found.
Ice and water protection. Self-adhered water barriers are used in vulnerable areas according to the project design, applicable requirements and manufacturer instructions. In Michigan, freeze-thaw cycles and ice-dam conditions make eaves, valleys and penetrations especially important areas to think about.
Underlayment. Underlayment provides a secondary layer beneath the shingles and is part of the moisture-management strategy for the roof.
Flashing. Chimneys, sidewalls, valleys, skylights, roof-to-wall intersections and penetrations can become leak points when flashing is missing, deteriorated or poorly integrated. Replacement is an opportunity to address those details instead of simply roofing over them.
Ventilation. Intake and exhaust ventilation help manage attic heat and moisture. Michigan guidance specifically emphasizes attic airflow as one way to reduce conditions that contribute to ice dams. Ventilation should therefore be reviewed as part of the roof system, not sold as a decorative add-on.
Shingles, starter and ridge materials. The visible roofing layer should be installed as a coordinated assembly, using products and methods appropriate to the selected manufacturer and roof design.