Sash windows

[AJS2018]

I’m going to attempt to make a sash window incorporating modern sash/pulley mechanisms, any book or video recomdations?

AJ

 

[rogxwhit]

Did you mean spring balances? Because there's nothing modern about pulleys!

Pulleys can work very nicely, but in these double glazed times the design means that you have an uninsulated weight box down each side.

Or are you listed?

Any joinery textbook should cover weight and / or balance spring construction, according to its publication date.

ps they are very satisfying to do, somehow!

 

[mr rusty]

Hi - there's a thread here Machinery Advice - Spindle Moulder/Tenoner and Bandsaw or Table Saw with the dims of the ones I made. I used Accoya from Arnold Laver - expensive but easy to work with and very stable for external joinery. Seals and beads from reddiseals, some hardware from mighton products.

I also have a thread with the whole saga over at Screwfix forum https://community.screwfix.com/threads/talk-box-sash-windows.183451/

I dry glazed with internal beads. I used qwood clip-in staff beads and glazing beads (or reddiseals equivalent) and plastic parting beads. Traditionalists may frown, but it has been a very successful design. If you are going for DGU, make sure you leave space for enough lead weight!. Lessons learned by me - the pulleys can be a draught point if the box is not well sealed and the cavity wall is ventilated. Traditional waxed sash cords stretch more than you think they will with lead weights.

 

[Ollie78]

Stick to weights and ropes. Spiral balances are a horrible invention and will only give you problems, they are never as smooth as weights and pulleys.
The only reason to use spring balances is if you have no room for the boxes.

Ollie

 

[rogxwhit]

I always enjoy cutting the pocket in a weight box! But it remains that the box is a huge cold bridge in insulation terms given that it is a hollow space without much wood between either the inside or the outside of the building, along with being vented to the room through the pulley hole of the bottom sash ...

 

[Ollie78]

I always enjoy cutting the pocket in a weight box! But it remains that the box is a huge cold bridge in insulation terms given that it is a hollow space without much wood between either the inside or the outside of the building, along with being vented to the room through the pulley hole of the bottom sash ...

I am not sure its as much of a cold bridge as it may initially seem.

44mm of wood has the same level of insulation as a double skin cavity brick wall ( if I remember rightly ) so 20mm inner and outer cheek is quite a bit of insulation and they are separated by a nice big air gap inside the box. I always put a full plywood back on the boxes which helps against draughts through the pulley as well.
Also the box itself is sitting inside one skin of brick or stone to begin with, unlike a casement where the frame is often in the opening with no overlap which provides a direct bridge.

Be interesting to use a thermal camera on one to see after installation but I don`t have one.

Ollie

 

[rogxwhit]

All boxes should be backed! It's a default. I'm not on about draughts through the pulley hole - just that it vents to the room, and there will be considerable convection currents within the 100 x 50 or whatever box ...

Also room air can enter the box (through that same pulley hole), and condense against the colder outer lining ...

I love boxed sash windows, I love making them, but in modern terms ...

 

[AJS2018]

Did you mean spring balances? Because there's nothing modern about pulleys!

Pulleys can work very nicely, but in these double glazed times the design means that you have an uninsulated weight box down each side.

Or are you listed?

Any joinery textbook should cover weight and / or balance spring construction, according to its publication date.

ps they are very satisfying to do, somehow!

I’d like to consider both but it will probably end up being a spring construction.

 

[mr rusty]

but it will probably end up being a spring construction.

I think it depends whether you are replacing existing box sash windows or making a sash window to fit in to a standard opening. If you make a spring balance window for a recessed reveal you will also have to sort out the space where the boxes used to be....

 

[rogxwhit]

With balances you can go for slimmer linings - a different look, but you get more glass. There's only about 30 or 40mm in it each side, depending. Or you could keep traditional width linings and layer in some insulation behind the stile.

If the balances are to recess into the stiles, which I prefer because it doesn't weaken the sash frames, I'd make the stiles from 50mm stock ...

 

[rogxwhit]

A good textbook used to be Purpose Made Joinery by Frank Hilton, Longmans. Relatively modern, but I can't remember whether he dealt with spring balances. And might be a bit hard to track a copy down?

​

 

[Doug71]

The Mumford & Wood website is a good source of information. Find the product you want (probably spring sash windows) then you can see and download all their CAD drawings showing all the sections and dimensions they use, you do have to log in but it's straightforward and definitely worth a look.

https://www.mumfordwood.com/

 

[Ollie78]

Whitehill have some drawings as well on their website.
They would of course like you to purchase thier "window system" but you don't need to.

Ollie

 

[AJS2018]

Thanks to everyone, some interesting advice.
AJ