⚡ Flashing Length Estimator – Roofing Flashing Calculator
Calculate total flashing length required for valleys, chimneys, skylights, and roof edges
Calculate the total flashing length required for your roofing project. Includes edges, walls, valleys, skylights, dormers, and optional extras. Proper flashing is critical to waterproofing, preventing leaks, and ensuring roof durability.
Result will appear here
💡 Tip: Always add 5–10% extra flashing for overlaps and cutting.
📐 Flashing-specific guidance will appear here after calculation.
✅ Best Practices:
• Use step flashing where roof meets vertical walls.
• Counterflashing required for chimneys.
• Continuous valley flashing improves water shedding.
• Overlap flashing pieces at least 2–4 inches.
• Nail only at top edge to allow water runoff.
• Use corrosion-resistant metals (galvanized, aluminum, or copper).
• Seal all joints with roofing cement.
• Check code for required flashing around penetrations.
• Skylights and dormers demand custom flashing kits.
• Replace damaged flashing immediately — leaks spread fast.
• Store flashing flat to avoid bending/warping.
❓ FAQ - Flashing Questions
Q: What is roof flashing?
Thin metal pieces installed to prevent water intrusion at joints, valleys, and penetrations.
Q: Which material is best?
Aluminum is cost-effective, galvanized steel is durable, copper lasts longest but is expensive.
Q: How much overlap is needed?
Typically 2–4 inches, but always check manufacturer instructions.
Q: Do chimneys need special flashing?
Yes — use step + counterflashing system for watertight seal.
Q: Can flashing be reused?
Usually no — old flashing may be corroded or warped, risking leaks.
Q: How often should flashing be inspected?
Twice a year and after severe storms.
Q: What’s the most common flashing failure?
Improper overlap, missing sealant, or corrosion.
Q: Do codes require flashing?
Yes — around chimneys, skylights, walls, and valleys.
Q: What’s drip edge vs flashing?
Drip edge covers roof edges, flashing seals penetrations/walls.
Q: Can caulk replace flashing?
No — caulk is a temporary fix, flashing is structural protection.