Parapet Flashings: Don’t Make These Costly Mistakes!

Parapet Flashings: Avoiding Expensive Errors

A well-designed and installed parapet flashing system is crucial for protecting your building from water damage. Improper installation or material choices related to parapet flashings can lead to costly repairs down the line. This guide will highlight common mistakes made with parapet flashings and provide instruction on how to avoid them.

Understanding Parapet Flashings and Their Role

A parapet is a low protective wall along the edge of a roof. Parapet flashings are the weatherproofing system that protects the intersection between the parapet wall and the roof. Their primary function is to prevent water from penetrating the wall and roof assembly. When parapet flashings fail, it can lead to leaks, structural damage, and mold growth.

Common Mistakes in Parapet Flashing Design and Installation

Many problems arise from flawed design or poor installation practices. Paying close attention to these areas is key to a long-lasting, effective system of parapet flashings.

Inadequate Overlap and Seams

Parapet flashings rely on overlapping pieces to create a waterproof barrier. Insufficient overlap leaves seams vulnerable to water infiltration.

• The Problem: Short overlaps (less than 4 inches is generally not recommended) allow water to be driven under the flashing by wind and rain. Poorly sealed seams also create weak points.
• The Solution: Always adhere to manufacturer specifications for overlap requirements. Use appropriate sealant designed for the flashing material.

Incorrect Material Selection

Choosing the wrong material for your parapet flashings can lead to premature failure. Factors to consider include climate, roof type, and building codes.

• The Problem: Using incompatible metals can lead to galvanic corrosion. Cheaper, less durable materials may degrade quickly under UV exposure or extreme temperature fluctuations.
• The Solution: Consult with a roofing professional to determine the best material for your specific application. Common materials include:
  • Aluminum: Lightweight and corrosion-resistant.
  • Copper: Durable and aesthetically pleasing, but more expensive.
  • Galvanized Steel: Offers good protection at a lower cost, but can rust if not properly maintained.
  • Stainless Steel: Highly durable and corrosion-resistant, suitable for harsh environments.

Improper Drainage

Proper drainage is essential for preventing water from pooling and causing damage. Parapet flashings must be designed to effectively channel water away from vulnerable areas.

• The Problem: Flat or poorly sloped flashings allow water to accumulate. This can lead to premature deterioration of the flashing and underlying materials. Clogged drainage pathways (e.g., scuppers) also contribute to water buildup.
• The Solution: Ensure the flashing is sloped adequately to direct water towards drainage points. Regularly inspect and clean scuppers and gutters to prevent blockages. Consider incorporating drip edges to further protect the edge of the parapet.

Failure to Properly Integrate with Roofing Membrane

Parapet flashings must be seamlessly integrated with the existing roofing membrane to create a continuous waterproof barrier.

• The Problem: Gaps or discontinuities between the flashing and the roofing membrane provide entry points for water. This is particularly common around penetrations such as pipes and vents.
• The Solution: Use compatible sealants and adhesives to create a watertight seal between the flashing and the roofing membrane. Properly detail and flash all penetrations.

Neglecting Thermal Movement

Materials expand and contract with temperature changes. Failing to accommodate thermal movement in the design of parapet flashings can lead to stress and cracking.

• The Problem: Rigidly installed flashings without expansion joints can buckle or crack under thermal stress.
• The Solution: Incorporate expansion joints at appropriate intervals to allow for thermal movement. Use flexible sealants that can accommodate expansion and contraction. The specific spacing of the expansion joints will depend on the material used for the parapet flashings.

Best Practices for Installation

Following best practices during installation is crucial for ensuring the long-term performance of your parapet flashings.

1. Surface Preparation: Thoroughly clean and prepare the substrate before installing the flashing. Remove any debris, dirt, or loose materials.

2. Proper Fastening: Use appropriate fasteners that are compatible with the flashing material and the substrate. Ensure fasteners are properly spaced and tightened.

3. Sealing Details: Pay close attention to sealing details, especially around corners, penetrations, and seams. Use high-quality sealant specifically designed for roofing applications.

4. Regular Inspection and Maintenance: Regularly inspect parapet flashings for signs of damage, such as cracks, corrosion, or loose seams. Address any issues promptly to prevent further damage.

Troubleshooting Common Parapet Flashing Problems

Identifying problems early can save time and money. Here’s a quick guide to common issues:

Problem	Possible Causes	Solution
Leaks at Seams	Inadequate overlap, failed sealant	Re-seal seams with appropriate sealant, consider replacing flashing.
Corrosion	Incompatible metals, lack of maintenance	Clean and protect metal, consider replacing with corrosion-resistant material.
Cracking	Thermal movement, material degradation	Install expansion joints, replace damaged flashing.
Water Pooling	Insufficient slope, clogged drainage	Improve slope, clear drainage pathways.
Blistering of Roofing Membrane	Moisture trapped beneath flashing, material incompatibility	Remove and replace flashing, ensure proper ventilation.

So, keep these pitfalls in mind when dealing with parapet flashings. Get it right, and your building will thank you!