I came up with this for my nesting box lid and wanted to see what people thought about it. It's not perfect, but I think it should keep the girls dry. I'm hoping the 16" overhangs keep most of the water out and this should only be needd when it's raining sideways...
I searched around Home Depot for rubber strips to seal the hinge area and I was just about to leave with a piece of garage door bottom seal when I stumbled on a roll of shower pan liner. The shower pan liner was four foot wide and cost $5/ft so I got two 1'x4' pieces for $10 and I was on my way.
My nesting box lid is about six feet long so I had to take the two pieces and 'glue' them together to make a 7.5' long piece (6" overlap). I used some leftover black RTV sealant and spread a thin layer on the over lap and left it sit overnight with some weight on it.
I took off the trim board above the nesting box lid and screwed the rubber on about halfway up.
Then I reattached the trim board and put the lid on temporarily to see how much to trim off the bottom of the rubber.
I put the nesting box lid on and mounted the hinges through the rubber.
Then I put on a row of 'ridge shingles' to cover up the hinge and the rubber. Because it isn't truely a ridge cap, you will need to get some roofing tar and glue down the top and side of each ridge shingle.
I'm also planning on putting some clear silicone along the top of the trim board in between each batten to really seal it up nicely.