I installed roofing felt on my shed about four weeks ago and it has been rained on a few times. No leaks inside the shed, and hoping to shingle next week.
I understand that the felt should not have been exposed that long so I am wondering if I need to do anything extra at this point to strengthen it. I already installed the drip edge properly (over felt at rakes, under at eaves). Do I apply some kind of tar coating for reinforcement?
As long as you did the final nail-down with the roofing disks, you'll be fine. Down here in hurricane territory, South Florida, they can have roof felt on for a few months before shingles and it's fine. Just make sure it's dry before moving around on it to shingle it.
I agree with JACK. It's probably fine if it's not visibly damaged. I thought I'd point out that felt isn't really a waterproofing layer. While it is somewhat waterproof, the zillions of nail or staple holes in it are vulnerable. Its purpose is mostly to isolate the shingles from the roof deck.
Also, most products will specifically state how much exposure time is permitted for the warranty. That's a good indication of what is ok.
Finally, if you think it's too degraded, replace it (or just double it up). You don't apply goo to rectify a fairly inexpensive problem like that.
