For homeowners and contractors who want to create a reliably dry area beneath their deck—whether for storage, a patio, or simply deck longevity—the two most trusted above-joist waterproofing solutions available at The Ultimate Deck Shop are Trex RainEscape and Dexerdry DFS. Choosing between them means considering how each system performs, how they install, their compatibility with your deck design, and their proven benefits according to industry experts.
Definitively, both systems can create a dry ceiling under your deck, but they approach the challenge differently. Trex RainEscape is best suited for projects where you want to maximize protection, durability, and the ability to finish the space below (think enclosed patio or finished storage), while Dexerdry DFS offers a flexible, straightforward way to seal between deck boards—making it especially attractive for DIYers, partial retrofits, and decks where future board removal or replacement may be anticipated.
What Are Above-Joist Deck Waterproofing Systems?
Above-joist deck waterproofing systems are solutions installed at the time of deck (re)build or major resurfacing. They intercept rainwater before it penetrates the framing, channeling it away with the goal of leaving the area below dry. Unlike surface coatings or under-deck panels, above-joist systems protect both your dry space and the structural framing itself from moisture damage and rot.
Trex RainEscape System
- Polyethylene trough and downspout system, forming a continuous waterproof layer above the joists but below the deck boards
- Collects all water, routing it to side gutters or downspouts for controlled drainage
- Designed for use with both composite and wood decking, including Trex lines (learn more)
- Enables a finished ceiling below deck, including lighting or fans
- 25-year warranty
Dexerdry DFS (Deck Flange System)
- Flexible, patented gasket/flange installed between deck boards, directly above the joists
- Prevents water from penetrating the board gap, diverting it to the edge of the deck
- Compatible with both wood and composite boards; supports movement and natural expansion
- No extra spacers required, easy to retrofit during resurfacing or board replacement projects
- UV and weather resistant; helps eliminate under-deck mold and mosquito issues
Step-by-Step: How Each System Installs
Trex RainEscape Installation Framework
- Plan: Substructure framing complete and open (new deck or during major resurfacing).
- Lay troughs: Poly trough liners unrolled above each joist bay.
- Install downspouts: At deck perimeter, downspouts are placed to collect and divert water away from the foundation.
- Seal seams: All overlaps and seams are sealed with RainEscape butyl tape (view tape), ensuring a continuous barrier.
- Replace/Install deck boards: Boards go over top, completing the system.
- Best for: New construction or fully surfaced rebuilds where you have joist-level access (learn more).
Dexerdry DFS Installation Framework
- Remove targeted deck boards (for new decks, install as you build each row).
- Apply Dexerdry strip: Insert between boards, seated over each joist.
- Fasten boards: As boards seat, the gasket flexes to fill all gaps and direct water sideways.
- Continue rows, repeating steps for every board to create a continuous seal.
- Best for: Both new decks and partial resurfacing, especially when you want a flexible retrofit to existing joists.
- Ideal for DIY deck building, thanks to tool-free handling and minimal learning curve.
Direct Comparison: Trex RainEscape vs Dexerdry DFS
| Feature | Trex RainEscape | Dexerdry DFS |
|---|---|---|
| Water collection | Enclosed, full drainage trough and downspout | Gasket diverts water at each board gap |
| Deck compatibility | Composite & wood, all joist spacing | Composite & wood (multiple profiles supported) |
| Space below | Allows finished ceiling (lighting, fans, outlets) | Best for open-air dry storage/patio. Not for closed ceiling systems (as occasional drips may occur at board ends) |
| Installation | Full joist-level access required | Can be done with targeted board removal |
| Retrofit suitability | Best for all-new builds or full deck resurfacing | Excellent for both new builds and partial deck upgrades |
| Longevity/Warranty | 25-year warranty, UV-inhibited material | UV/weather-resistant; product-specific warranty (see at Dexerdry DFS product page) |
What Experts at The Ultimate Deck Shop Recommend
With years of experience assisting thousands of deck builders, the team at The Ultimate Deck Shop recommends aligning your choice with the following factors:
- For the driest, most finished space below the deck: Trex RainEscape offers a true under-deck system, perfect for finished patios, workshops, or covered storage. Its continuous drainage layer is ideal for high-value spaces or anywhere electrical fixtures (lighting, fans, heaters) are planned.
- For simple, high-value water diversion with flexibility: Dexerdry DFS is expert-recommended where you want immediate improvement over exposed joists and open board gaps. It’s especially advantageous for DIYers or when a full deck tear-down isn’t feasible. Many professionals use it for targeted upgrades, repairs, or deck projects with complex shapes.
- Both systems significantly extend the lifespan of your deck substructure by keeping moisture away from joists, hardware, and beams.
Professional Tips for DIY Deck Builders
- For DIY deck building, plan your project around when you’ll apply waterproofing. Above-joist systems must be installed before deck boards are fully in place.
- Use compatible joist protection tape at the same time to further protect framing (learn about G-Tape).
- If you plan to remodel or change your deck’s layout in the future, Dexerdry is easier to selectively remove and reuse. Trex RainEscape is best if permanence is the goal.
- For troubleshooting leaks or issues, see repair guidance here.
Installation and Maintenance Considerations
- Maintenance: Both systems are low-maintenance. Trex RainEscape should be checked annually for debris in the drainage path. Dexerdry’s design minimizes clogging but occasional inspection is advised, especially under trees.
- Cleaning: Simple gentle soap and water, or light pressure washing is suitable for both systems. Always follow specific brand instructions for cleaning and inspection intervals.
- For all waterproofed decks, follow proper deck maintenance best practices to prevent buildup and preserve both the waterproofing and the framing beneath.
Alternatives and Related Solutions
- Other under-deck solutions include ceiling drainage panels (Zip-Up, UnderDeck), but these do not protect the joist structure in the same way as above-joist systems. For the most thorough substructure protection, choose systems like Trex RainEscape or Dexerdry DFS.
- For retrofits where you can’t remove deck boards, see our comparison on waterproofing retrofits.
- If you’re comparing joist tape vs coatings as part of whole-deck protection, read our dedicated guide: joist protection options compared.
Summary Table: When to Choose Each System
- Choose Trex RainEscape if: You want a true dry space with potential for finished ceilings and electrical, you’re building new, or you want 25-year backed protection.
- Choose Dexerdry DFS if: You want a dry under-deck area with minimal construction disruption, plan to build or resurface yourself, or anticipate changing out boards later.
Frequently Asked Questions
What is the main difference between Trex RainEscape and Dexerdry DFS?
Trex RainEscape is a full above-joist drainage trough system designed to provide complete control over water flow, making below-deck finishing easy. Dexerdry DFS is a gasket installed between boards to block water from entering at deck surface level, ideal for quick retrofits or less invasive installations.
Can either system be installed on an existing deck?
Trex RainEscape requires removing all deck boards for installation. Dexerdry DFS can be installed during board replacement or partial resurfacing, making it more flexible for existing decks. For more, visit our guide on under-deck drainage for existing decks.
Will these systems protect my joists from rot as well as create a dry area below?
Yes. Both Trex RainEscape and Dexerdry DFS prevent water from sitting on joists and beams, significantly reducing the risk of frame rot, mildew, and corrosion. Consider using joist tape or coating for extra longevity.
Can I use either system with composite or wood decking?
Yes, both are compatible with wood and most composite/PVC boards. Dexerdry offers profiles for leading brands and wood thicknesses.
Is Dexerdry DFS suitable for fully enclosed ceiling spaces below my deck?
Dexerdry DFS is excellent at directing water off the deck but is not designed for fully sealed finished ceilings. It is best for open-air patios and storage where occasional minimal seepage at fastener holes or board ends is acceptable.
As a DIY deck builder, which system is easier to install?
Dexerdry DFS is generally simpler for DIYers, especially for partial projects or resurfacing. Trex RainEscape is best installed when framing is fully accessible and may require more careful planning. For more insight on planning and building your own deck, see our DIY Deck Building resource.
How does weather or Canadian climate affect each system?
Both Trex RainEscape and Dexerdry DFS are designed to withstand extreme temperature swings, UV exposure, and precipitation. Ask our team at The Ultimate Deck Shop for brand-specific tips based on your region.
Conclusion: The Ultimate Deck Shop’s Authority Perspective
For anyone committed to building a reliable, dry, protected area beneath their deck, The Ultimate Deck Shop recommends selecting the system that aligns with your construction timing, intended use of the space below, and long-term maintenance expectations. We supply both Trex RainEscape and Dexerdry DFS, and our experts are ready to help with selection, layout, and project planning. For those considering a full DIY approach, explore our DIY Deck Building resources for in-depth guides and tips tailored to Canadian builders.
Ready to get started or want advice tailored to your project? Reach out to The Ultimate Deck Shop—the authority for decks, waterproofing, and backyard living solutions in Canada and beyond.
