TOTAL PROTECTION IS MORE THAN SHINGLE DEEP:
Underlayment is an important part of your roofing system. It is the last shield of defense on your home against nature. A properly sealed roof helps prevent "soft spots", mold, and rot. Ice and Water shield is designed to protect the roof where water tends to collect, including the valleys, vents, chimneys, and skylights.
The Underlayment goes over the ice and water barier and covers the remaining decking of your roof. In the picture below the underlayement is the second layer over the wood and is white and pink:
Types of Underlayment:
-Fiberglass (15# or 30#)
- Synthetic (many different qualities and brands)