1. Footprint of the house, in square feet
The ground-floor area the roof covers — not the total living area of a two-storey house.
2. Roof pitch
3. Roof shape
4. Storeys
5. Material
BasisNew Hampshire installed cost bands, 2026: Galvalume standing seam $12–$16/sq ft, aluminium standing seam $14–$20, steel metal shingles $8–$14, asphalt shingle $6–$10, exposed-fastener panel roughly $5–$12 (national). Snow retention $1–$3/sq ft. Pitch factors 1.06 shallow, 1.25 moderate, 1.45 steep. Full sourcing on the cost page. This is an orientation range, not a quote — a quote needs eyes on the roof.
Four Things That Move It
Complexity, by a distance
Valleys, dormers, hips, chimneys, stacks, skylights, and the junctions where a connected ell meets the house. Each is flashing, and flashing is where the hours and the failures both are. A simple gable runs long uninterrupted panels; a converted camp with four additions runs short panels into six different valleys.
Pitch, twice over
It increases the actual area — a steep roof is 45% larger than its footprint against 6% for a shallow one — and it makes the work slower and the staging more involved. A roof too steep to walk is a different job.
Material and gauge
Galvalume to aluminium is a real step, and copper is another category entirely. Panel gauge, seam profile and finish system all move the number within a material.
What is under the deck
Not knowable until tear-off. On an older roof something is usually found. What matters is that the repair rate is agreed before the tear-off rather than discovered during it — ask for it on the quote.
What is not in this estimate: tear-off and disposal of the existing roof, deck repair, structural work, gutters, skylight replacement, and snow retention. Those are real costs and they belong as separate lines on a quote, not folded invisibly into a per-square-foot figure.