The case of the rotted window sills

Some time in the last sixty years, aluminum window screens were installed over the windows.  They were screwed into place and painted.

The paint bridged across the gap between the bottom of the aluminum screen frame and the 2-by wooden sill.

Rain slanting in would penetrate the screen, hit the window and run into the sealed space between the aluminum frame, the sill and the window.

How did I figure this out?

After I washed the outsides of the windows with a hose.  It flooded the space and ran in over the inside window sill.

Across the floor and down the hall.  Gotta love the vintage linoleum.

The fix cost ten cents per window.  I pried the aluminum frame up and shimmed it with two nickels.  Nickels are almost exactly 2 mm thick.

The gap bridged with paint.  Modern paints are almost a gel.

I was not successful scraping the paint out immediately after painting.  The paint just flowed back in.  I was more successful going back about 45 minutes later.  The paint had solidified enough by then that it did not flow back.