I was inspecting a home the other day and when I met with the client, and asked her, as I always do, “Is there anything you may have noticed, that you have questions about.”
This is not only to address their specific fears and concerns but also so I am given a heads up on a potential defect. My client and their agent directed me over to a the window sills. Right along the edge that is closest to the window a small swell could be noted along the entire 
length. The sills were Medium Density Fiber (MDF) board and MDF is a wonderful historic indicator of past leakage. The swelling definitely appeared like moisture absorption however no other indicators were present. If the windows were allowing storm water to enter the home there should be staining at the top of the window and there was none. There should have been more evidence of leakage on the south windows, since that is where most all of our wind driven rain comes from and all of the windows on every side of the home seamed to show evidence of this swelling.
That night while I was writing the report and thinking about what might have been going on with the sills, I realized the only thing different about these windows is that there was not a bead of caulk between the widow and the window frame. The carpenter had done such a great job all of the reveals where beautiful and perfect. The painter thought maybe he didn’t have to caulk.
As the previous owner cleaned the sills with a damp cloth that small gap would suck up moisture. The MDF where it had been painted was relatively resistant to moisture damage so no issues on the painted surface however the gap that had been perfect enough to not caulk exposed the vulnerable MDF that was not even primed. (sponge)
The moral of the story is: Caulk. (as a verb and noun) Gaps, even perfect ones, will trap water and cause cosmetic issues that will be challenging to repair.
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