he Truth About Deck Drainage Systems

When it comes to building or upgrading a deck, the surface materials and railing often steal the spotlight—but what’s underneath matters just as much. At Centennial Custom Decks, we know that a properly designed deck drainage system can protect your investment, expand usable space, and prevent long-term damage. Especially in Colorado, where snowmelt and sudden downpours are common, waterproofing your deck is more than a nice-to-have—it’s essential.

Imagine This...

It’s a crisp Saturday morning in Denver. Coffee in hand, you head outside to enjoy the shade beneath your deck—only to step into a puddle. The cushions are soaked. The space smells musty. That vision of a cozy outdoor lounge? Gone.

It’s a scenario that plays out more often than most homeowners expect—and one that can be avoided entirely with the right drainage system in place.

What Is a Deck Drainage System?

A deck drainage system is a setup that channels water away from the deck boards and framing. It can be installed above the joists (before decking goes down) or below them (for existing decks). These systems direct moisture into gutters or outflow pipes, helping keep the area underneath dry and usable.

There are two main types:

• Over-joist systems: Installed between the joists and decking, offering maximum protection by keeping the joists dry.
• Under-joist systems: Installed beneath the deck joists, ideal for retrofit projects and keeping the area below dry—but not the joists themselves.

Why Drainage Matters in Colorado

In the Denver Metro Area, freeze-thaw cycles are no joke. Water that seeps between deck boards can pool, freeze, and expand, causing cracks, warping, and even structural issues over time. Without proper drainage:

Joists can rot prematurely

Mold and mildew can grow in dark, damp areas

Underdeck areas become unusable for storage or living space

Long-term damage may void warranties or reduce resale value

Investing in waterproofing decks upfront can save homeowners thousands in repairs and help maintain the deck’s integrity year-round.

Designing a Functional Underdeck Space

One of the best perks of a deck drainage system is the ability to create a livable space below. With water properly diverted, the underside of your deck can be transformed into:

A shaded lounge area

Dry storage for outdoor gear or tools

A covered patio with lighting, fans, or TVs

A grilling station that works rain or shine

Adding ceiling panels, soffits, or decorative finishes can elevate the space, especially when paired with lighting or electrical features.

Waterproofing That Works With Your Deck Design

Whether you're https://www.centennialdecks.com/services/composite-decks or updating a wood deck, waterproofing solutions can be customized to fit the structure. Centennial Custom Decks offers expert guidance to help you choose the right system based on your deck's material, slope, and intended use underneath.

Our team ensures drainage systems are installed with care, using premium materials that stand up to Colorado’s unique climate. The result? A longer-lasting deck, fewer maintenance headaches, and more ways to enjoy your outdoor space.

Ready to Protect Your Deck?

Water management is one of the most overlooked aspects of deck design—but one of the most important. If you're planning a new deck or looking to upgrade an existing one, now’s the time to think about drainage.

Centennial Custom Decks serves the Denver Metro Area with expertly designed, built, and waterproofed outdoor living spaces. Call (720) 273-2527 to schedule your consultation and take the first step toward a smarter, drier, and longer-lasting deck.

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