At least, I think so. It was warm and dry, so I left it until after lunch before I started, as planned, on my wood store roof repair. The problem was exactly as I’d surmised. I could see immediately that the sealant that I’d used for the first part of the first roofing felt joint that I did, which is right above where the water had been penetrating, had indeed been too thin, had already succumbed to the weather and had lifted in places.
Repairing it wasn’t too difficult and didn’t take too long either. I warmed the joint up with my electric heat gun and carefully lifted it up with a thin bladed paint scraper. I then applied a bit more heat inside the overlap to make sure that it was dry and used an old paintbrush to force in some more sealant, which is now thick and tar-like, so that when I pressed the upper roofing felt edge downwards onto the lower sheet, it oozed back out again. Then I added even more sealant to the surface outside the joint so that the edge of the top sheet was totally covered and enclosed by the stuff, which I think will this time ensure a weather-proof seal.
When I originally did the other joint higher up on the roof, the sealant had already thickened up, so although it didn’t really need it, I did the same with that as well. I’m pretty sure that what I’ve now done will give me a fully watertight roof again and solve my water ingress problem. And by the look of the sky over to the west as I type this, it could well get its first test this evening, so I hope that I’m right 😉