Measuring sash window glass for replacment

[600rob]

I want to replace and reglaze 6 small panes of glass in a sash window myself.

When measuring the new glass to order how do I ensure make the most accurate measurements with the window and old glass is still in place?

I've taken measurements from inside of the window which are approx 175x480mm per pane but there is a small area of glass that is not visible from the inside as it rests on the glazing bar.

I need to ensure each pane of new glass is large enough to sit on the glazing bar yet at the same time need to small enough that it fits into the space between glazing bars with sufficient clearance all around the aperture into which it fits.
I can't get outside to measure from the outside as the window is on the 1st floor and I don't have access to the garden as the property is split into flats.

Hopefully this all makes sense

Any tips on how I can accurately measure up before I take the window out?

Also, how do you measure the thickness without removing/breaking one of the old panes?

 

[OwainDIYer]

Sash windows should be hingable inwards for cleaing and reglazing. At least they are in Scotland.

To measure the glass remove a small amount of putty on each edge, just enough to see the edge of the glass.

To measure the thickness measure the distance from the outside of the sash (wood) face to the glass, and from the inside of the sash to the glass, and subtract those two from the thickness of the wood.

 

[600rob]

thanks owain.

unfortunately the windows don't hinge inwards. Only vertical movement up/down as far as i can tell.

Looks like i might have to pop one of the staff beads out in order to temporarily remove the window to take accurate dimensions.

 

[OwainDIYer]

You can probably make them hinge inwards

https://www.mightonproducts.com/products/sash-window-hardware/window-assistance/simplex-swing-system

 

[600rob]

That looks interesting. Its the same company where i was going to order some new beads from so i might get one of these kits aswell and give it a try

Thanks again