I have a 10'x12' deck and want to enclose the lower area for a storage room. For this to work I need to have the deck surface water tight. I would replace the old deck board with new. The only decking I have found that's water tight is aluminum Lockdry (
I'm thinking of using composite decking and cutting a 1/2" spline pocket in the edge of each board. Then installing it using pure silicone in each pocket with a 1/4" x 1 1/4" spline between each board. Leaving 1/4" of the spline showing between each board.
I would use that galvanized angle iron with elongated holes along each joist to screw the boards down from underneath. Placing the screws w/washer in the middle of the elongated hole would allow the entire deck to expand and contract with the weather.
Any comments or ideas.