Caulk is often the first thing people reach for when they see a gap
outside. Sometimes that’s right. Sometimes the opening is a designed
drainage path, or the sealant is failing because the trim behind it
moves or stays wet. I prefer to understand the joint before sealing
it.
On a dry day, look around windows, doors, trim joints, and
penetrations for cracking, separation, and staining. Photograph the
location and check the product instructions for the surface, joint
width, preparation, and curing weather. Remove failed material and clean
the joint as directed. Painting over loose sealant won’t make it adhere.
If there is soft wood, recurring staining inside, or an opening in a
complex wall assembly, have the cause evaluated before cosmetic
repairs.
Leave drainage alone
Many window and cladding systems have weep openings or intentional
gaps. Filling them can trap water. The Department
of Energy’s caulking guide discusses choosing and applying caulk for
air sealing, but the details of an exterior wall still depend on its
assembly. If you cannot identify a joint’s purpose, ask a qualified
window or exterior contractor.
Keep a note of what you sealed and revisit it after a season. Sealant
is a maintenance material, not a permanent waterproofing plan.
Persistent leakage, loose flashing, or movement calls for repair of the
underlying condition.
I keep local exterior contractor contacts on Helpful
Resources. My Homeowner
Tools & Supplies page has general upkeep supplies; choose the
actual sealant from the window or material manufacturer’s
recommendations.