Goberco Under Deck Drainage System -Z/50/12- 50' Long Roll, for 12'' Joist Spacing, 30 Mil Thick Black Trough, Create Dry Below Deck Storage Pack of 2

On-top of joists installation - keep framing and under deck area dry.Easy to install - 1. Staple on top of joists 2. Self sealing tape over joints 3. Screw downspouts to water evacuation holes.Material cost is about $ 2/s.f. (Goberco membrane is about $1.4/s.f., self sealing joist tape is about $0.4/s.f. , regular downspout + plastic gutter + roofing screws are low cost).Save Time / Reduce Leaks - Fold against house wall for flashing (reduce leaks at ledger board) - Deep channel valley between joists - Regular downspout redirect water flow into a gutter (prevent water dripping / no special downspout needed). U.S. patent # 9,453,338