Outdoor security lighting

[Captorofsin1]

I know I'm probably going to get make fun of for this one. I just want to make sure that I'm on the right route.

I've been tasked to replace outdoor motion sensing security lights where there are existing lights. These lights are mounted on surface mount weatherproof junction boxes.

Believe it or not, I actually took the time to read the instructions (Even by looking at the light fixture beyond self-explanatory how to install). Just that I noticed most of these fixtures come with a gasket but they also require you (as per instructions) do you silicone sealant around the perimeter. That doesn't make any sense to me gasket and silicone. I've never used silicone around ever seen silicone used when I replaced one of these fixtures before. And I've never read the instructions on them because it was always self-explanatory. I never even thought to use silicone where there's a gasket.

Thoughts?

 

[NoahsArc]

I've always siliconed mine, leaving a small drip gap at the center-bottom.
I'm not sure what they're telling you to silicone there, but the penetration in the siding of the house should not allow water in, that's what I silicone, not the fixture itself usually. So silicone around the fixture, not the fixture itself, though obviously one edge should be on the fixture, the other edge on the siding. Big flex is my preference, as there will be a different in materials and thermal expansion.

Think of water sheeting down the siding into the fixture, make it so that none will slide under it and into the interior of the siding.