I had some joint issues with my nest box. I used silicon that says "no shrink". BS! No matter how much I used, it always shrunk away leaving small cracks for the water to find a way in. Then I found TremSeal. It's a rubberized sealant normally used in roofing operations and made by Tremco. I used it all along the seams, around the tops of nails and screws and wow, does it work. It stays somewhat pliable, yet seals completely. I put it on yesterday morning and it rained lightly yesterday afternoon. No leaks, 100% adherence. Good stuff!