TimberTech® DrySpace Under-Deck: Product Review, Pros & Cons

TimberTech DrySpace is a solid extruded vinyl deck drainage system that attaches to your existing deck joists and routes rainwater away from the area beneath your deck. 

It comes in Bone and White, ships as a complete kit, carries a 25-year limited warranty, and each kit covers six joist bays. 

If you have a second-story deck and the space underneath floods every time it rains, this product was built for exactly that situation.

What the TimberTech DrySpace Actually Does

The TimberTech DrySpace panels sit beneath your deck boards, between the joists. 

Rain passes through the gaps in your decking and hits the V-shaped vinyl panels, rather than dripping onto your furniture or soaking into your framing. From there, the panels funnel the water outward, away from the house.

The solid extruded vinyl holds up against UV exposure and sustained moisture without cracking, swelling, or warping. The off-white finish also brightens what is usually a dark, underused space, giving the area beneath the deck a finished look.

Persistent moisture in partially enclosed spaces dramatically accelerates mold growth. Deck joists and rim boards are especially vulnerable. A working deck drainage system deals with that problem before it becomes structural.

What Comes in the TimberTech DrySpace Kit

Each DrySpace kit includes every component needed for a six-bay installation:

• V-shaped drainage panels that nestle between joists and collect water as it falls
• Main support rails that form the track the panels attach to
• Combo brackets for securing the rails to joists with corrosion-resistant screws
• Ledger F brackets that anchor the system at the ledger board, closest to the house
• Double combo brackets for multi-section installs with overlapping rails

Kits for 12-inch on-center spacing come in 12-foot lengths. Kits for 16-inch on-center spacing are available in both 12-foot and 16-foot lengths.

If you want context on how DrySpace fits into a broader TimberTech build, our blog on TimberTech composite decking covers the full product line.

The DrySpace Installation Process

Getting DrySpace in is not complicated, but it requires precision. 

The whole system needs to slope at 1/8 inch per foot, pitching away from the house. If that pitch is off, water pools in the panels instead of draining out. That one detail is the cause of most of the failed installations.

Here’s a general step-by-step:

1. Snap a chalk line at the correct pitch along each joist before any brackets go up
2. Attach the ledger F brackets at the house-side end of each joist bay
3. Fasten the main support rails with corrosion-resistant screws
4. Slide in the V-shaped drainage panels, trimmed to length
5. Maintain a minimum 3-inch gap before the fascia for ventilation and water exit

That gap at the fascia is non-negotiable. Blocking it traps moisture. 

Most contractors also recommend pairing DrySpace with a gutter at the drip edge, especially on larger decks, to carry runoff further from the foundation. 

Indiana’s residential construction code requirements around drainage and moisture management are worth reviewing for any deck project, and your local building authority can confirm what applies in your municipality.

Pros and Cons of TimberTech DrySpace

Pros:

• Retrofits onto existing joists. Most deck drainage systems require new construction. DrySpace attaches to existing deck framing, which saves significant time and money for anyone upgrading a finished deck.
• The vinyl is genuinely durable. Solid extruded vinyl resists moisture absorption, corrosion, and the UV degradation that causes cheaper systems to yellow and crack within a few seasons.
• Long-term reliability you can plan around. A 25-year warranty on a product with few mechanical failure points is a meaningful commitment.
• Turns dead space into an outdoor living space. Under a second-story deck, DrySpace creates a dry, furnished area that adds real square footage to how you use your yard.

Cons:

• The pitch requirement is unforgiving. Eyeballing it will cost you. The chalk line step is tedious, but skipping it means standing water.
• Six bays per kit. On a large deck, costs stack up quickly. Budget for multiple kits and factor in the additional combo brackets.
• Only two color options. Bone and White are clean and work in most settings, but there’s no match available for darker or stained deck aesthetics.

FAQ

Does DrySpace work on an older deck?

Yes. It attaches directly to existing deck joists, so retrofitting it is fully supported. No structural changes required.

What joist spacing does it need?

DrySpace is engineered for 12-inch or 16-inch on-center joist spacing. Other spacing is outside the product’s supported range.

Is this a DIY project?

TimberTech includes full instructions with every kit, and installation guides are available online. That said, managing the pitch over longer spans, trimming panels accurately, and handling ledger bracket placement tend to go better with someone who has framing experience. A bad pitch means pooling, which defeats the whole system.

How does it handle mold and mildew?

The vinyl panels are inherently mold-resistant. The bigger protection is structural: keeping the joists dry removes the damp conditions that mold needs to get started on the wood framing underneath.

Which composite brands pair well with DrySpace?

Any deck built on 12″ or 16″ on-center joists is compatible. For a comparison of composite decking brands worth building on, our post on the best composite decking brands is a good place to start.

Maybe Just Let Someone Else Handle All of This

There’s a version of this weekend project that turns into a three-week headache. 

If you’re in Westfield, Noblesville, Carmel, or the wider Indianapolis area, the team at Decks On Point handles full deck builds with integrated drainage systems, so none of this lands on your plate. 

Take a look at what we do on our deck building page, or simply call us at (317) 903-2431 or message us here.