On Fri, 21 Mar 2008 18:33:18 -0700 (PDT), wrote:

I just added a new room to my house. I have installed the windows, and
now I need to know how far the window sill should protrude past the
left and right interior window trim.

You might want to plan ahead and think about what you'll be using the
sills for, if anything.

On the sill in this room, I have a little AM-FM radio, a wmls web
radio and music player, and where the sill wasn't deep enough, I
nailed a board so that I can have a candlabra in the window.

I think my sills are 3 inches, but it's not always enough.

In my bedroom I have a fan on the sill. Hard to find a fan with a
base small enough, and even then I had to nail one corner into the
sill because the fan is top-heavy (looks like it was riveted to some
big machine, to cool the operator.

I am running out of space on the bookshelves next to the bed for all
the audio and video things and alarm clocks and books and lamp, so I
might have to put the next radio on the window sill. Might have to
make that one deeper too, but probably not.