What Goes Into a Complete Roofing System?

The shingles are the most visible part of a roof, but they are only part of the work. A useful replacement estimate also describes the surface underneath, water-management details at edges and openings, and the ventilation plan.

Explore the parts of a roof

Select the details in GAF’s diagram to learn about its roof-system components. The diagram explains product roles. Your written proposal should identify the products and details that apply to your own roof.

Start below the shingles

The deck provides the surface for the roof covering. During a replacement, removing the existing covering can expose conditions that were not visible before work began. Ask how any damaged decking will be photographed, priced and approved. Underlayment and any specified leak barriers belong in the scope as well.

Pay attention to the transitions

Edges, valleys, chimneys, walls and pipes need their own details. A proposal that names only the shingle leaves important questions unanswered. Ask which flashing will be replaced, which existing parts will remain, and how the contractor will address roof-to-wall junctions and penetrations.

Discuss ventilation as a system

Have intake and exhaust reviewed together for the actual attic and roof arrangement. The right approach depends on the building and the product requirements. More vents alone do not establish that a ventilation design is appropriate.

A written-scope checklist

• Removal of the existing roof covering and disposal.

• Deck assessment and the process for approving concealed repairs.

• Underlayment, leak barriers and starter products where specified.

• Shingles, ridge caps, flashing and penetration details.

• Intake and exhaust ventilation, cleanup and applicable written warranty terms.

See a documented replacement with deck repairs

Read our roof replacement estimate guide

Discuss your roof replacement

Prepared by Barnes N’ Roofs, New Braunfels, Texas. Updated September 17, 2026.