It’s one of the most common questions our Outdoor Living Specialists hear: “So once it’s installed, the space under my deck will be completely waterproof, right?”
It’s an understandable assumption. The name has “RainTight” right in it, and the finished result looks a lot like an indoor ceiling. But RainTight Underdecking is a water diversion system, not a waterproof enclosure. That difference matters, and understanding it up front helps you plan a space you’ll love for years.
What “Water Diversion” Actually Means
When it rains, water falls through the gaps between your deck boards. Without an underdeck system, that water drips straight onto whatever is below, whether that’s a patio, furniture, or bare ground.
RainTight Underdecking is designed to direct water away from the area below.. Interlocking aluminum panels collect the rainwater and channel it into a built-in gutter system with a downspout, which carries it away from the area beneath your deck. The result is a clean, finished ceiling and a space below that is noticeably drier, cleaner, and more usable.
In short, the system manages the water coming down through your deck. It is designed to redirect water, not to seal off the space from the outdoors.
Why It Isn’t “Waterproof”
RainTight helps manage water coming through the deck above, but it does not seal the area from the elements on all sides. Because it remains an outdoor space, there are a few things worth keeping in mind.
Rain can still blow in from the sides. The underdeck system covers the ceiling, not the open sides of your patio. Wind-driven rain can reach furniture near the edges, just as it would on any covered porch.
The space is still exposed to outdoor humidity. Moisture in the air, morning dew, and temperature swings affect an underdeck area the same way they affect any open-air space.
Water has to go somewhere. The gutter and downspout are what make the system work, so keeping them clear of leaves and debris helps everything flow the way it should.
One item worth mentioning, during torrential downpours or periods of unusually heavy rainfall, the system can become inundated with more water than it is able to drain at once. When that happens, water may temporarily overflow from the gutters or other areas of the system until the rainfall subsides and the system can catch up.
None of this is a flaw. It’s simply how a covered outdoor space behaves, and it’s why we’re careful to describe RainTight as a water diversion system.
How to Plan the Space Below Your Deck
Knowing what the system does helps you get the most out of it. A few tips from our team:
- Choose outdoor-rated furniture, rugs, and cushions. They’re built to handle humidity and the occasional stray splash from blowing rain.
- Use outdoor-rated fans, lighting, and electrical fixtures. The finished ceiling is a great place for a fan and lights, and fixtures made for covered outdoor spaces are the right fit.
- Think about the sides. If you want to make the space feel more enclosed or add protection from bugs, a screen room can be a great addition. We can install special blocking with the underdeck system to accommodate the addition of one of our screen rooms.
- Keep up with simple maintenance. RainTight panels are designed to help channel water and debris through the system, which makes routine upkeep easier. Periodically checking the gutters and downspout for leaves or debris is recommended.
What Sets RainTight Apart
RT Construction is the manufacturer of the RainTight Underdeck System, which means we maintain quality control from fabrication through installation. Every system is custom-made to fit the dimensions of your deck for an efficient install and a polished, finished look.
The panels are high-quality aluminum, built for strength, stability, and long-term performance, making them a durable alternative to vinyl and PVC products. You can choose from three stock colors (White, Black, and Sierra) or three custom colors (Bronze, Coastal Dune, and Pewter) to complement your home. Whether you’re building a new deck or upgrading an existing one, RainTight can turn wasted space into a functional area for relaxing, entertaining, and everyday life.
Frequently Asked Questions
Is RainTight Underdecking waterproof?
No. It is a water diversion system that collects water falling through your deck boards and channels it into a gutter and downspout, keeping the space below much drier. The open sides of the space are still exposed to the weather, and during periods of extremely heavy rainfall, the system may temporarily take on more water than it can drain at once.
Will the area under my deck stay dry?
Our system is designed to keep the area below your deck substantially drier, but it is still an outdoor space. Blowing rain and outdoor humidity can still reach the area, just like any covered porch or patio. During torrential downpours, some temporary overflow from the gutters may also occur until the system is able to catch up.
Can I add RainTight to an existing deck?
Yes. Each system is custom fabricated to fit your deck, whether it’s new construction or an existing structure.
What colors are available?
Stock colors are White, Black, and Sierra. Custom colors include Bronze, Coastal Dune, and Pewter. Contact your Outdoor Living Specialist for custom color pricing.
Ready to Make the Most of the Space Below Your Deck?
Our process is simple: we meet with you to plan your space and take detailed measurements, send a personalized quote, schedule your project once approved, custom fabricate your system, and complete a professional installation with warranty and maintenance information provided afterward.
Contact RT Construction to schedule a consultation.
St. Louis Office: (636) 357-8385, 851 Pic Parkway, Wentzville, MO 63385
Lake of the Ozarks Office: (573) 240-4049, 29545 State Hwy Y, Rocky Mount, MO 65072
Email: info@buildrt.com | Web: buildrt.com
