Black Diamond Landscape & Outdoor Living
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Elevated Decks

Under-Deck Drainage for Utah Homes: RainEscape vs. DrySpace

Two systems, two positions in the assembly, one goal: keeping the space below an elevated deck dry and usable. Here is how they work and when each makes sense.

Multi-level TimberTech Coastline deck with upper living area — Millcreek renovation
Multi-level TimberTech Vintage Coastline deck — Millcreek renovation. Elevated deck design with integrated drainage planning.

The problem both systems solve

An elevated deck creates a covered space below it — but without a drainage system, that space fills with water every time it rains. Water drips through the deck boards, saturates the framing, and makes the area below unusable for anything except storage of things you do not mind getting wet.

Trex RainEscape and TimberTech DrySpace both address this problem, but they do it from different positions in the assembly. Understanding the architectural difference helps you make the right choice for your project.

Trex RainEscape — above-joist system

RainEscape is installed above the joists, before the decking goes down. Troughs are laid between the joists and connected to downspouts that route water away from the structure. Water that falls on the deck surface is collected in the trough system before it ever reaches the space below.

Because the system is installed above the framing, it integrates cleanly into new construction. The troughs become part of the framing assembly, and the downspouts can be routed to a drainage point that suits the site.

Trex publishes a 25-year limited residential warranty on RainEscape.

TimberTech DrySpace — under-deck system

DrySpace is installed below the decking and joist area. It collects water that passes through the deck surface and routes it away from the space below. Because it is installed beneath the framing rather than within it, DrySpace can be applied to existing elevated decks as well as new construction.

The under-deck position means the system is visible from below — it becomes part of the finished ceiling of the lower-level space. This can be addressed with a finished soffit or ceiling treatment, which is worth planning for if the lower-level space is intended for seating or entertaining.

TimberTech publishes a 25-year limited residential warranty on DrySpace.

Which system is right for your project?

The two systems are not interchangeable, and the right choice depends on several factors.

For new construction, RainEscape's above-joist position integrates more cleanly into the framing design. The troughs are part of the structure from the start, and the downspout routing can be planned alongside the rest of the drainage design.

For an existing elevated deck where the framing is already in place, DrySpace may be the more practical option. It can be installed without dismantling the existing deck structure.

The framing configuration, the height of the deck, the intended use of the lower-level space, and the site's overall drainage design all factor into the recommendation. We discuss these as part of the deck planning scope.

Planning for lower-level use

If you want to use the space below an elevated deck for seating, storage, an outdoor kitchen, or any other purpose, that needs to be part of the planning conversation from the start — not an afterthought.

The drainage system is one piece. The electrical rough-in for lighting and ceiling fans, the access points, the finished soffit or ceiling treatment, and the connection to the rest of the outdoor-living design all need to be coordinated. A lower-level outdoor room that works well is designed as a room — not as a byproduct of the deck above it.

Our Millcreek renovation is a good example of a multi-level deck system where the upper and lower levels were designed together as part of an integrated outdoor-living scope.

TimberTech Coastline lower viewing deck — Millcreek renovation

Installed example — Millcreek

TimberTech Vintage Coastline — multi-level deck

A hillside renovation with upper and lower deck levels integrated into a Belgard Steeplecrest retaining wall system. The deck levels were designed together as part of the overall outdoor-living scope.

See the Millcreek project

Planning an elevated deck?

The Deck Planner includes a lower-level use question — include it from the start so the drainage and framing design can account for it.

Open Deck Planner

Under-Deck Drainage — Common Questions

Black Diamond answers to the questions we hear most often when homeowners are planning elevated decks with usable space below.

Yes — when the deck is planned around that use from the beginning.

An elevated deck that is designed with drainage, lighting, and lower-level access in mind can create a genuinely useful outdoor room beneath it. Depending on the height and configuration, that space can accommodate seating, storage, a finished soffit, ceiling fans, landscape lighting, or even an outdoor kitchen setup.

The key word is "planned." A drainage system — whether Trex RainEscape or TimberTech DrySpace — needs to be integrated into the framing design, not retrofitted after the deck is built. The electrical rough-in for lighting and fans, the access points, and the finished ceiling treatment all need to be part of the original scope.

If you are thinking about using the space below an elevated deck, include that in the planning conversation early. It changes the framing design, the drainage specification, and the overall scope.