November 2, 2026

Summary: Beneath shingles, a roof relies on the deck, underlayment, and ice and water shield to block moisture that shingles alone cannot stop. Synthetic underlayment resists tearing, while felt costs less. Self-adhering membrane protects eaves, valleys, and penetrations. Proper selection, placement, and installation prevent leaks, rot, and costly repairs over a roof’s lifespan. Most homeowners