Box sash windows

[meccarroll]

It's not that it's a bad idea it's just not how it was done. If it was proof against it ever rotting I would consider it but after 100+ years these windows can basically turn so dry and twisted water can penetrate In a multitude of spots. Making them with a housing is my favourite bit oddly it's just a rock solid joint with the sizes set by the inside of both housings.

I totally understand why the original sliding sash windows used a wedge and groove at the junction between the pully stile and cill.

The wedge tightens up the joint to prevent shrinkage and stop water running in the groove but over time shrinkage plays it's part and water inevitably makes it's way into the groove and the rot starts. It was known many years ago to be a weak point and the wedge was a form of preventing shrinkage opening the joint.

It is normally only the corners of the cill on a sliding sash window that go rotten and it does usually take some years to happen so it's overall not a bad design.

 

[Jim mcgrath]

Thanks for all the photos. There’s a good Youtube video where he demonstrates making the housing in the cill for the pulley stile to sit into. It’s titled “how to make box sash windows in oak part 1” (skip to about 13.40)

 

[mr rusty]

Are you wanting to make them totally traditionally? or do you want a window with modern performance taking DGU? If you go on Mumford and Wood's website you can register and download their CAD drawings. (I'm sure that isn't what they are there for......) I used their conservation range as the basis for 8 windows I made for our house. https://www.mumfordwood.com/product/conservation-range/box-sash-windows. It didn't take much to adapt their profiles to standard router cutters and to take off-the-shelf beadings and seals.

I used Accoya, domino'd joints, internally beaded and dry glazed with 24mm DGU, and with weight pockets on the inner lining not the pulley stile, with a variety of different seals, clip-in parting and staff beads. Painted in Teknos aquatop, five years on and they are still perfect.

The photo is my test piece when I was working out clearances for the seals I was using.