Professional Flashing Design Tips

Accurate measurements are the foundation of effective flashing design. Even small errors can lead to significant water intrusion problems down the line.

• Always measure twice, cut once
• Account for thermal expansion in your measurements (typically 1/8" gap per 10' of metal)
• Use our flashing app's measurement tools for precise dimensions
• Consider the pitch of the roof in your calculations

Successful flashing design requires understanding how water will flow across and around penetrations in varying weather conditions.

• Design with heavy rainfall in mind, not just average conditions
• Account for wind-driven rain coming from multiple directions
• Remember that water can travel uphill due to capillary action
• Always overlap flashing pieces in the direction of water flow

The way flashing components overlap is critical to water management. Follow these guidelines for proper overlap:

• Maintain a minimum 4" overlap for most applications
• Increase overlap in high-precipitation areas or steep slopes
• Ensure upper pieces always overlap lower pieces
• Use sealant between overlapping metal pieces when appropriate

Remember that improper overlapping is one of the most common causes of flashing failures. When in doubt, provide more overlap rather than less.

Not all flashing materials work well together. Consider these compatibility issues:

• Avoid direct contact between dissimilar metals (e.g., copper and aluminum) to prevent galvanic corrosion
• Ensure sealants are compatible with both flashing materials and substrates
• Consider climate conditions when selecting materials (some perform better in extreme heat or cold)
• Check manufacturer recommendations for compatibility with roofing materials