Roof Decking Calculator

Calculate roof decking (sheathing) panels needed for your roof. Accounts for roof pitch, waste, and standard 4Γ—8 sheet size.

🏠 Roof Decking Calculator

Results

Flat Area720.00 sq ft
Pitch Multiplier1.118
Actual Roof Area804.98 sq ft
Total (+ waste)885.48 sq ft
4x8 Sheets28 sheets

πŸ’‘ How to Calculate Roof Decking

Roof decking area is larger than the footprint because of the pitch. Multiply the flat area by the pitch factor: √(1 + (pitch/12)Β²). A 6/12 pitch increases area by 11.8%. Common decking is 4Γ—8 ft CDX plywood or 7/16-inch OSB (32 sq ft per sheet).

Add 10–15% for waste β€” more for complex roof shapes with valleys, hips, and dormers. Decking must be staggered (joints offset by at least 4 feet) and fastened with 8d nails every 6 inches on edges and 12 inches in the field.

A 30Γ—24 ft gable roof at 6/12 pitch: flat area = 720 sq ft Γ— 1.118 = 805 sq ft. With 10% waste = 886 sq ft Γ· 32 = 28 sheets of 4Γ—8 plywood or OSB.

Roof Decking Calculator FAQ

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