Shingle replacement is measured in squares (1 square = 100 sq ft). Every component — tear-off, underlayment, ice and water shield, shingles, ridge cap, drip edge — is priced separately per square or per linear foot.
Roof Area Formula
Roof squares = (Footprint sq ft × Pitch factor) ÷ 100, then add 10–15% waste
Example
2,000 sq ft footprint × 1.118 (6:12 pitch) = 2,236 sq ft ÷ 100 = 22.4 squares + 12% waste = 25.1 squares → order 26
Waste factor: 10–20% depending on roof complexity
Measure on the roof — not from the ground. Walk each plane and measure L × W. For complex roofs, sketch a diagram with each plane labeled. Sum all planes for total area. Apply the pitch factor from the pitch factor table.
Flat (1:12) = 1.003. 4:12 = 1.054. 6:12 = 1.118. 8:12 = 1.202. 10:12 = 1.302. 12:12 = 1.414. A 6:12 pitch adds 11.8% to footprint area. Pitch factor is the difference between a profitable and unprofitable complex roof bid.
Simple gable roof: 10% waste. Moderate complexity (one hip, one valley): 12–15%. High complexity (multiple hips, dormers, intersecting valleys): 15–20%. Waste covers ridge cuts, hip cuts, valley cuts, and starter course.
Tear-off: price per square ($75–$150/sq). Synthetic underlayment: price per square ($30–$50/sq). Shingles: price per square at markup ($140–$200/sq for architectural). Ridge cap: price per LF of ridge and hip. Ice and water shield: price per LF of eave and valley. Drip edge: price per LF of all eave and rake edges.
Flashing (chimney, skylights, walls): $200–$600 each. Pipe boots: $50–$100 each. Ventilation (ridge vent, static vents): $150–$400 each. These are frequently under-counted on complex roofs.
Always add a conditional decking repair line
Include 'Decking replacement if needed — $X/sheet of 7/16 OSB' as a conditional line. You cannot know deck condition before tear-off. Pre-authorizing the rate prevents a mid-job negotiation.
Count pipe boots, vents, and flashings from the ground with binoculars
Use binoculars during your estimate visit to count every penetration. Missing two chimney flashings ($400 each) can eliminate your profit on a mid-size job.
Include ice and water shield beyond code minimum
Building code requires ice and water shield at the eave line. Best practice (and warranty requirement on many manufacturer programs) is also to install it in all valleys. Specify this in your estimate — it differentiates you from low-bid competitors.
Use satellite measurement software (EagleView, Hover, Nearmap) for steep or unsafe roofs. These tools generate accurate pitch-adjusted square counts from aerial imagery for $15–$40 per report. The cost is recovered in one accurately-priced job.
Architectural (dimensional) shingles: 4 bundles per square (25 sq ft per bundle). Three-tab shingles: 3 bundles per square (33 sq ft per bundle). Always verify with the manufacturer's bundle coverage — it varies by product.
A complete estimate includes: tear-off and disposal, decking inspection (conditional repair line), synthetic underlayment, ice and water shield (valleys and eaves), drip edge (eaves and rakes), starter strip, shingles, hip and ridge cap, pipe boots, any flashing replacement, and dumpster rental. Missing any of these creates scope disputes.
Each additional layer of shingles to tear off adds $50–$100/square to your tear-off price. Two-layer tear-off is roughly 1.5× a single-layer. Three-layer tear-off (common on older homes) is 2–2.5×. Note the layer count during your site visit and price it explicitly.
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