How do I figure how many bundles of architectural shingles to order for a roof that measures out to 2,650 square feet, with two valleys and a couple hips?

Quick answer: Order 100 bundles (≈33.3 squares).

The math

1. Field area: 2,650 ft² ÷ 100 = 26.5 squares.
2. Waste factor: Hip/valley roofs run 12–15 % waste. Use 15 % for cut-up geometry. 26.5 × 1.15 = 30.5 squares*.
3. Starter & hip/ridge: Starter: ~1 bundle per 120 lin. ft. of eave/rake. Hip/ridge cap: 1 bundle covers ~20–25 lin. ft. (architectural cap shingles). Typical 2,650 ft² roof ≈ 250–300 lin. ft. total eave+rake+hip+ridge → 3–4 bundles starter + 3–4 bundles cap*.
4. Total squares: 30.5 + ~0.7 (accessories) ≈ 31.2 squares.
5. Bundles: Most architectural shingles = 3 bundles/square. 31.2 × 3 = 93.6 bundles → round up to 100 bundles (keeps dye-lot intact, covers damage/mis-cuts).

Code/Install notes

• IRC R905.2.8.5: Valleys require 36"-wide Type II (ASTM D226) underlayment or self-adhered membrane centered on valley. Order extra underlayment accordingly.
• IRC R905.2.7: Hip/ridge shingles must be manufacturer-approved for cap use; don’t field-cut 3-tab.
• Nailing: 4 nails/shingle (6 in high-wind zones per R905.2.6).
• Drip edge (R905.2.8.1) and ice barrier (R905.1.2) where required.

Pro tip: Confirm bundle coverage on the specific wrapper—some “premium” lines are 4 bundles/square. Adjust count before ordering.

To determine how many bundles of architectural shingles to order for a 2,650 sq ft roof with valleys and hips, follow this practical, code-informed approach:

1. Base Calculation: Architectural shingles are typically sold in bundles covering 33.3 sq ft per bundle (standard for 3-tab or architectural shingles; verify your product’s coverage on the bundle label). → 2,650 sq ft ÷ 33.3 sq ft/bundle ≈ 79.6 bundles → round up to 80 bundles for the field area.

1. Waste Factor for Complexity: Valleys and hips increase waste due to cutting and fitting. - Standard waste: 10% for simple roofs. - With 2 valleys + hips: Add 15–20% waste (per NRCA and IRC R905.2.1 guidelines for complex roofs). → Use 18% as a conservative midpoint for valleys/hips. → 2,650 sq ft × 1.18 = 3,127 sq ft adjusted area. → 3,127 ÷ 33.3 ≈ 93.9 bundles → round up to 94 bundles.

1. Additional Considerations: - Starter strips and ridge caps: These are separate products — don’t include them in shingle bundle count. Order starter strips per linear foot of eaves (usually 1 bundle per 100–120 lf) and ridge caps per hip/ridge length (typically 1 bundle per 20–25 lf). - Always buy 1–2 extra bundles for future repairs or mistakes — order 95–96 bundles total to be safe. - Check manufacturer specs: Some architectural shingles (e.g., GAF Timberline HDZ) cover 32–35 sq ft/bundle — confirm your product’s exact coverage.

Final Answer: Order 95 bundles of architectural shingles. Note: If your roof has steep pitches (>6:12) or irregular shapes, add another 5%. For valleys, ensure you’re using woven or closed-cut method per IRC R905.2.8 — improper valley installation causes leaks. If unsure about flashing or underlayment, consult a licensed roofer — valleys and hips are high-risk zones. (Word count: 248)