The main cost factors
Roof size
Roofing is measured in “squares” — one square covers 100 square feet of roof surface. Roof area is larger than the home’s floor area because of slope and overhangs, so it has to be measured.
Pitch and complexity
Steeper roofs take longer and need more safety equipment. Hips, valleys, dormers, multiple levels, and lots of edges add labor and material compared with a simple gable roof.
Material
Architectural asphalt shingles, designer shingles, and metal all have different material and installation costs. The product line you choose — and the accessories that go with it — affect the price.
Tear-off and layers
Removing the existing roof is part of the job. More than one existing layer means more labor and disposal.
Decking
Damaged or rotted roof decking has to be replaced. Its full condition is only known once the old roof is off, so a good estimate explains how any replacement decking is priced.
Flashing, valleys, and penetrations
Chimneys, skylights, walls, and vents each need proper flashing. Replacing worn flashing rather than reusing it adds cost but protects the most leak-prone parts of the roof.
Ventilation
Correcting poor attic ventilation — adding intake or exhaust — can be part of a replacement and affects the scope.
Access and site conditions
Tight lots, landscaping that needs extra protection, or limited driveway space for dumpsters and deliveries can affect logistics.
What a complete estimate should list
- Tear-off and disposal of existing layers
- How damaged decking is handled and priced
- Underlayment and ice and water protection
- Flashing replacement and details
- Ventilation work
- Shingle or material line and color
- Ridge, starter, and edge components
- Cleanup and site protection
- Warranty information
How to compare quotes
Put the estimates side by side and check each item above. Ask what’s included, what’s an allowance, and what would change the price. The lowest number isn’t always the lowest cost if it leaves something out.