A Collins window that could be salvaged with timber slips and a flannel. Once all the rot had been identified and machined out leaving exposed sound wood I could go about fitting the replacement parts.
This can become a lengthy project depending on the rot present and it is not always economically viable to do this. The only exception would be if a window or door was from a grade 1 listed property.
However this was economically viable and cost less than half that of a replacement window.