If a deck rail spans more than 5 ft. or so, I think it’s important to support the bottom rail, using something that won’t rot. I’ve tried various approaches to this problem. The drawing illustrates my favorite solution. Instead of wood, I use short lengths of PVC pipe, cut with a chopsaw into little cylinders.
For a 2x bottom rail, I use 1-1/4 in. O. D. (outside diameter) pipe, cut into lengths that fit snugly under the rail. To hold them in place, I run a 7-in. square-drive gutter screw through the bottom rail, through the PVC cylinder, and well into the deck, burying the screw head. This works particularly well because I use a minimum 3-in.- deep bottom rail.
The PVC cylinders are strong and unobtrusive, they hold paint well, and they won’t deteriorate or wick water into the rail.
Forrest McCanless, via email, None