On Jul 27, 5:37*pm, "Bob F" wrote:
When I repaired a deck, I decided to put a strip of 15lb tar paper over the
joists before attaching the deck boards. The tar paper was about 1/2" past the
edge of the joist, and then lightly folded down to form a drip edge. My theory
is that the tar paper will tend to run rainwater away from the joists, and drip
it slightly away from them, extending their life. Any opinions out there?

We used strips of shingles at the cottage. Worked well.