Should I caulk this crevice that formed between materials in an exterior door frame?

Question

I'm planning to repaint this exterior door that leads to my deck. It's a metal door, with some kind of decorative moulding along the outside edges - it feels like a dense plaster-like material (maybe a heavy duty plastic?), but I don't know for sure what it is.

Whatever the case, the wooden stop in-between the two is peeling badly, and I'm planning to sand down the wood, and then prime the door, stop, and moulding before applying a new coat of paint. There's a gap between the stop and moulding that formed as a result of age and the door sitting in direct sunlight, so I'm questioning if I should apply some paintable caulk here first:

I'm questioning if I should apply some paintable caulk between the stop and moulding first to keep moisture and bugs out. Are there any cons to doing that? Such as covering up some other underlying problem, or trapping water that might find some other way to get in the door frame?

Answer 1

What you are calling a "decorative moulding" is known as Brick mould. It is probably made of PVC.

Having 2 different materials, (wood and PVC) they will expand and contract differently. So your need a very flexible caulk.

Scrape away any loose paint and debris. Wipe the area clean and caulk with a polyurethane caulk. The polyurethane is more flexible than latex and easily paintable, unlike silicone.

The poly takes a day to dry and need to be cleaned with mineral spirits, but will last much longer than latex.