Next I applied a double bead of sealant to the roof. I want it to squeeze out of the joint, but due to the roof thickness and vent spigot, there is no opportunity to clean up on the inside, so I put a smaller bead towards the inside:
The vent is carefully dropped into place. I but a small dab of sealant in each screw hole, This will wet the screw threads and seal under the head:
I installed the screws, making them up just barely snug. I do not want to squeeze all the sealant out, a thicker joint allows for more movement without failure. There is a little bit squeezing out from under the screw heads too. Fantastic provides steel flat head screws, but I substituted SS oval head screws instead. A flat head will sink into the countersink on the flange, leaving a small pool for water to collect in a very vulnerable spot. The oval heads fill the countersink and shed water. Every little detail counts! I then raked the sealant off tight to the flange with a sharp cornered tool:
This is how it looks with the excess sealant removed. I want to remove all the sealant I can without undercutting the joint. I also wiped a bit around the screw heads, mostly this is the "obsessive attention to detail" of which I have been accused:
