Understand shingles, underlayment, flashing, ventilation and roof details with GAF’s interactive roofing-system guide.
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.
GAF parts of a roof
Explore roofing options with GAF’s interactive tool.
Interactive resource supplied by GAF. Open the tool in a full window.
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
See the layers together
Read the assembly from the wood deck upward: secondary protection, edge components, field shingles and ridge treatment. This TAMKO illustration is one system example; flashing and ventilation details still need their own plan. Source: TAMKO HailGuard brochure. View original detail.
| Role | Example to discuss |
|---|---|
| Secondary layer | Synthetic Guard or another underlayment specified for the assembly. |
| Roof edges | Compatible starter and edge details. |
| Main covering | Heritage, Titan XT, StormFighter FLEX or HailGuard as specified. |
| Hips and ridges | Compatible cap products, including any warranty-required products. |
| Airflow and transitions | A ventilation plan plus flashing, valleys and penetration details. |
These examples explain product roles. They do not replace the existing GAF system tool above or establish that a mixed-brand system qualifies for a manufacturer’s enhanced warranty.
Source: TAMKO roof-system accessories
Shingles, metal flashing and an intersecting roof section working together as part of the roof system.
Prepared by Barnes N’ Roofs, New Braunfels, Texas. Updated September 17, 2026.
Visual guide additions reviewed September 18, 2026.