I have a front window that has about a 1/32 inch gap in the summer, but about a 1/4 inch gap in the winter. The original caulk completely came loose and allowed condensation from the window to get into the wall. Worried about this, I removed the caulk and re-caulked it this fall when there was only the small gap. The other day I noticed that the caulk had come free on one side already. I had scraped all the old caulk off and cleaned with alcohol before applying the new caulk. I used silicone caulk.
What is the trick for this? I have noticed that wherever a surface that needs to be caulked touched an outside wall that this is common. Any tips?
EDIT: the surfaces involved are the plastic window frame and a plastic window sill. The area needing caulked is similar to what is shown here (the lower right arrow) except the sill-surface is plastic. Or similar to this pic where the water is puddling (this is not my window)