When you pay for a “New Roof,” you aren’t just buying shingles. You are buying a complete Waterproofing System. If your quote seems high, it is likely because your contractor is installing all 5 critical layers rather than cutting corners.
Layer 1: The Decking (Sheathing)
This is the wooden foundation, usually OSB or Plywood sheets attached to your trusses.
Hidden Cost Warning: If your contractor rips off the old roof and finds rotted wood, they will charge extra (usually $60–$90 per sheet) to replace it. This is mandatory; you cannot nail shingles to rot.
Layer 2: Ice & Water Shield (The Code Requirement)
This is a sticky, rubberized membrane that self-seals around nails.
- Where it goes: In valleys, around chimneys, and along the bottom 3-6 feet of the roof (the eaves).
- Why: It prevents water from backing up under shingles when ice dams form in winter.
Layer 3: Underlayment
A synthetic or felt barrier that covers the rest of the wood deck. It acts as the final “catch-all” for any water that slips past the shingles during a hurricane or severe storm.
Layer 4: Starter Shingles
Amateurs often skip this. These are special shingles installed at the very edge of the roof to seal the first row down. Without them, wind can easily peel up your roof from the bottom edge.
Layer 5: The Shingles
The visible layer. Whether Asphalt, Metal, or Tile, this layer takes the brunt of the sun and rain. However, without the 4 layers beneath it, even the most expensive shingle will leak.