Q: My house was built in 1953. It was a ranch, until we enlarged it in 1996 to a Colonial. I just noticed that the sill in my original picture window has started to rot and the sills in the upstairs ...

Wood anywhere in your home is vulnerable to decay in the form of either wet or dry rot (both of which are actually fungal infestation). A rotten wooden door, floorboard, section of trim, window sill, ...