Flashing

What is Flashing?

Flashing is waterproof material (typically metal, rubber, or plastic) installed to direct water away from critical areas of a building's envelope. Flashing prevents water from entering the structure at joints, penetrations, and transitions between different materials.

Proper flashing installation is crucial for preventing water damage, rot, and structural issues in buildings.

Types of Flashing Materials

Metal Flashing

Most common and durable flashing materials:

Aluminum: Lightweight, corrosion-resistant, paintable Galvanized Steel: Strong, cost-effective, requires maintenance Copper: Premium material, long-lasting, develops protective patina Lead-Coated Copper: Superior durability, expensive Stainless Steel: Excellent corrosion resistance, modern appearance

Non-Metal Flashing

Rubber (EPDM): Flexible, good for irregular surfaces Modified Bitumen: Self-adhering, easy installation Plastic/Vinyl: Economical, limited lifespan Fabric-Reinforced: Combination materials for specific applications

Common Flashing Applications

Roof Penetrations

Vent Flashing: Around plumbing vents, exhaust fans Chimney Flashing: Step flashing and counter flashing systems Skylight Flashing: Integrated weatherproofing systems Antenna/Equipment: Sealing roof-mounted equipment

Roof Transitions

Valley Flashing: Where two roof planes meet Ridge Flashing: Along roof peaks and hips Eave Flashing: Drip edge along roof edges Rake Flashing: Gable end edge protection

Wall Applications

Window Flashing: Above and around window openings Door Flashing: Head flashing over doors Wall Penetrations: Through-wall services and fixtures Foundation: Where walls meet foundations

Flashing Installation Principles

Water Flow Management

Shed Water: Direct water away from vulnerable areas Overlap Properly: Upper pieces overlap lower pieces (shingle principle) Slope Adequately: Minimum slopes for positive drainage Seal Joints: Prevent water entry at connections

Integration with Building Systems

Continuous Barrier: Connect to other waterproofing systems Compatible Materials: Avoid galvanic corrosion Thermal Movement: Account for expansion and contraction Maintenance Access: Design for inspection and repair

Roof Flashing Details

Step Flashing

Used along roof-to-wall intersections:

• Individual pieces stepped up the roof
• Each piece overlaps the previous piece
• Integrated with shingles or roofing material
• Typically 6-8 inch pieces for standard applications

Valley Flashing

Channels water where roof planes intersect:

• Closed Valley: Shingles cover flashing completely
• Open Valley: Flashing remains exposed
• Woven Valley: Shingles interwoven across valley

Chimney Flashing

Complex multi-piece system:

• Base Flashing: Attached to roof deck
• Step Flashing: Up the sides of chimney
• Counter Flashing: Embedded in chimney mortar
• Cricket: Diverts water around large chimneys

Installation Best Practices

Preparation

1. Clean Surfaces: Remove debris and ensure dry conditions
2. Plan Sequence: Install from bottom up, following water flow
3. Check Materials: Verify correct type and quantity
4. Weather Conditions: Avoid installation in wet conditions

Installation Sequence

1. Base Layer: Install underlying waterproof barrier
2. Primary Flashing: Position main waterproofing element
3. Integration: Connect with roofing materials properly
4. Sealants: Apply where specified (sparingly)
5. Final Inspection: Verify all details are complete

Common Flashing Problems

Installation Errors

Improper Overlap: Water entry at joints Inadequate Fastening: Wind damage and displacement Wrong Materials: Compatibility and durability issues Poor Integration: Failure to connect with other systems

Material Issues

Corrosion: Metal deterioration over time Fatigue Cracking: Thermal cycling damage Sealant Failure: UV degradation and aging Physical Damage: Impact or maintenance damage

Design Problems

Inadequate Slope: Water ponding and backup Missing Details: Incomplete protection systems Thermal Movement: Expansion and contraction issues Maintenance Access: Difficult inspection and repair

Maintenance and Inspection

Regular Inspection Schedule

Annual: Basic visual inspection from ground Bi-annual: Detailed roof-level inspection Post-Storm: Check for damage after severe weather Seasonal: Spring and fall comprehensive reviews

Warning Signs

• Stains: Water stains on ceilings or walls
• Rust: Corrosion on metal flashing
• Cracks: Splits in flashing materials
• Loose Fasteners: Missing or backed-out screws
• Sealant Failure: Cracked or missing caulking

Repair Priorities

1. Active Leaks: Immediate temporary and permanent repairs
2. Deteriorated Materials: Replace before failure occurs
3. Preventive Upgrades: Improve inadequate existing details
4. System Integration: Ensure all components work together

Cost Considerations

Material Costs

• Aluminum: $2-$5 per linear foot
• Galvanized steel: $1-$3 per linear foot
• Copper: $8-$15 per linear foot
• Rubber/Modified: $3-$8 per linear foot

Labor Factors

Complexity: Simple details vs. complex intersections Access: Roof pitch and height considerations Integration: Time to properly connect systems Quality Level: Precision required for long-term performance

Building Code Requirements

Code Standards

IRC: Residential flashing requirements IBC: Commercial building standards NRCA: Industry best practice guidelines Manufacturer: Specific product installation requirements

Critical Requirements

• Minimum Overlap: Typically 4-6 inches
• Fastening: Type and spacing requirements
• Materials: Approved materials and compatibility
• Integration: Connection with other building components

Quality Assurance

Installation Standards

Workmanship: Proper techniques and attention to detail Materials: Use specified products correctly Documentation: Photo record of critical details Testing: Water testing where possible and appropriate

Long-term Performance

• Design Life: 20-50+ years depending on materials
• Maintenance: Regular inspection and minor repairs
• Replacement: Planned replacement before failure
• Upgrades: Improvements during reroofing projects