rotted window sill

[pinkertonpv]

I have a 20+ year old house with nice large wooden double hung double pane windows. I am going to install custom storm windows and need to replace some rotted brick molding and window sills on some. I can do the brick mold ok but I have some questions on the sills. I don't want to remove the windows so my initial plan is to remove as much of the rotted wood as possible and then insert new wooden sill until it matches up with the remaining solid wooden sill under the window. Nail, caulk, paint and then measure and install storm windows. Would Pressure treated wood be a good idea for the sill replacement? I would appreciate any advice and comments on the plan. Thanks.

[pushkins]

The window sashes need to be removed to replace the damaged sill, the sill and window frame sits on the house framing and then the window closes on the sill, The only way to remove the sill is to remove the sashes (or at least the lower sash, sometimes it can be done with the sash raised as high as it will go), cut out the sill and replace it in entirety. Trying to replace just the front section could work if you were able to cut it flat and level, then glue and screw the new front section in place, with it being caulked. It is certainly not an ideal fix and seldom works as a long term repair.
It really isn't all that much work to replace the entire sill, and much easier than trying to cut part of one out and replace with a section.