I reside in a victorian terrace house which once upon a time had box sash windows, the sash's have since been taken out but the frames have remained. In place of the sash's metal frames windows have been installed. I am looking at changing them now to PVCu windows, the thing that concerns me is that I do not wish to leave the old wooden sash framework in. What can I expect to find when I take this frame work out, as I do not want to open up a can of worms just before putting the new one's in? Happy New Year!