Good question that I have been thinking about in my painfully slow rebuilding of Victorian sash windows in our house.
The originals do not have the cut out and other comments suggest that it is a modern innovation.
I spend a lot o ftime in Cornwall and have noticed that many apparently original sash windows have this cut out, so I wonder whether it is more of a regional variation than a recent innovation, I don't know.
I am not sure which I prefer looks-wise. I would need to check on the windows at home, but I think that the extent to which the lining projects beyond the (stone) window opening is very small, whereas the windows I have looked at in Cornwall have more of the front face of the lining showing.
The one reason I have been considering following the cut out method is that on the pitifully few newly restored (and beautifully painted) windows I have done, I have noticed a build up of dust and grime in the corner behind the lining - I figured that the cut out would avoid this happening.
Two questions from earlier comments
RobinBHM":3m5mbv91 said:
I have sometimes stuck a small wedge behind the front facing so there isnt a water trap.
I am not quite sure how this would go - presumably shaped to sit on the slope of the cill, with the top level front to back and sloping in towards the middle?
ComfortablyNumb":3m5mbv91 said:
I'd leave it off because it's one piece of end grain that will always get wet and unless you repaint every year it will allow water into the front casing
I am not quite sure of the point here - is it suggested that the cut out is made or not? The way I see it:
- if the cut out is made, then the end grain of the cut out is in free air, so should not suffer unduly. Of course the cut out in the lining needs to run right to the bottom with a correspondingly smaller housing in the front of the cill.
- if the cut out is not made, then a wider section of the lining runs all the way to the bottom of the cill and yes that could become a weak point, if not properly maintained.
Would be interested to hear any further explanation.
Cheers