Can I put tin – corrugated metal – under top deck joists to prevent leaks onto bottom deck?
The snow/ice could absolutely be an issue if the snow melts from the deck boards onto the metal and refreezes repeatedly. Even if the metal is sloped, debris from the upper deck will collect on the metal. So, unless you have enough access space to sweep/hose the metal, the debris will build up and build up and build up! Enough space to sweep could attract critters. Maybe have a facia board or two that you can remove to insert a hose for debris flushing purposes and plan to do it at least once a year. Best to you!
