I designed this terrace edging to prevent rainwater from dripping down the painted surface below.  The photos show edging that has been in place more than a year. 

There are two pieces, spout and edging.  I used a spout every 3 meters or so, but it will depend on the area you are draining.  The edging is a very simple design that can easily be modified in your slicer to shorten, lengthen, or make non-90 degree ends.  If you cannot make necessary edits in your slicer, feel free to contact me for design help.  

I printed these in ASA – which is why the length is only 125 mm.  Beyond 125 mm length, the warpage was unacceptable.  If you print in PETG or other material with less warpage, you can probably print to the edges of your build plate.  The spout has no flat surface, and will require substantial support material.  

For installation, be sure to use a quality glue.  Apply the glue to the bottom edge AND the abutting edges to keep the water flow where you want it.