My home is 5yrs old and I have a 12inch section of window sill that appears to be rotting. The paint is cracking over this space. The window is near a sprinkler head that is very seldom used, and if it is used is only for abt 3 minutes at a time. This rotted section is in the corner of the window. I would like to repair the window. Tell me how I can do this. Thank you.