TREX RainEscape® 4x4 Post Flash: Leak-Proof Seal for Railing Posts

The TREX RainEscape 4x4 Post Flash is a specialized moisture barrier designed to seal the point where deck posts penetrate through your decking surface. By creating a tight, waterproof fit around 4x4 posts, this flashing component helps prevent leaks that could compromise your deck’s substructure over time.

Key Features

• Custom Fit for 4x4 Posts:
  Engineered to wrap snugly around nominal 4x4 posts (actual size: 3.5″ x 3.5″).
  
  
• Seals Out Moisture:
  Forms a watertight barrier to protect joists, framing, and the RainEscape system from water intrusion.
  
  
• Flexible, Durable Material:
  Made from UV-resistant plastic that withstands expansion, contraction, and harsh weather conditions.
  
  
• Easy to Install:
  Slides over posts and can be trimmed as needed with a utility knife for a perfect fit.
  
  
• Seamless System Integration:
  Designed to work in tandem with the full TREX RainEscape under-deck drainage system.

Specifications

• Fits: Nominal 4x4 deck posts (3.5″ × 3.5″ actual size)
• Material: Flexible UV-resistant plastic
• Colour: Black
• Brand: TREX
• Model #: POSTFLASH

Ideal For

• Decks with TREX RainEscape or similar drainage systems
• Sealing around post penetrations through deck boards
• DIY or professional deck builds and renovations

You May Also Need

• TREX RainEscape Downspout
  Directs water from joists to the drainage path
• TREX RainEscape Butyl Caulk
  Seals joints and connections
• TREX RainEscape Trough
  Core waterproofing membrane for the RainEscape system

Need Help?

Have questions about installation or planning your under-deck drainage system?
Contact our team or visit a Deck Store showroom for expert assistance.