I have found a couple of under deck methods of channeling water from a deck
but they all go under the deck boards or joists.
This won't work for my application.
Earlier I posted a possible way to water waterproof under a deck by cutting
spline pockets into the edges of composite deck board and using silicone to
seal the splines. A friend suggested using space ball (used to keep door
panels from rattling) to keep the spline centered and allow for expansion.
Another suggestion was to cut a piece of vinyl siding 'J' channel into a 'U'
channel with the top two bars of the 'U' about 1/2" long.
Then making a table saw cut into both sides of the bottom of each deck board
about 1/2" deep and 3/8" in from the edge.
As each board is installed, silicone would be inserted into each saw cut
then inserting the 'U' channel.
Water would fall between the deck boards and be channeled off the deck
through the 'U' channel.
I would use an under deck fastening system to secure the deck boards.
Does anyone think either of these methods would work?