Above the joists
An above-joist system is coordinated before decking covers the frame. This can fit a new build or certain redecking projects when the structure and product are suitable.
Trex RainEscape’s manufacturer FAQ explains that boards need removing for an existing-deck installation. Plan that work before choosing a new surface.
Below the joists
Below-joist products collect water beneath the framing and offer a different installation route. TimberTech DrySpace is one example for new or existing decks, subject to its requirements.
Review headroom, joist layout, obstructions, outlets and maintenance access. A finished ceiling should not prevent necessary review of the structure.
Trace discharge to the ground
Collection needs a suitable outlet and a practical destination for the water. Include the lower-level ground surface, doorway and walking routes in the discussion.
An open-sided area remains exposed to weather from the sides. A drainage system does not automatically create a sealed room or correct deterioration above it.
Compare complete options
State the exact product, removal work, gutters or outlets, finish ceiling and any lighting. Identify what is included and what is a separate trade or design scope.
Keep manufacturer installation and care information with the completed work. Product-specific details govern the actual installation.