Sash bar dimensions for historical windows

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steve355

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Hi

I am doing some research to discover the dimensions of historical sash window bars. I thought perhaps there might be an old joiner about who has repaired original windows and knows. In particular, I wondered if there was a standard size for the glazing rebate.

I have scoured all the old texts, Ellis, Hasluck etc and none of them really seem to say.

The dimensions I’m looking for are A, B and C below.
IMG_0777.jpeg

In general I know A+B+C. It’s given by the size of the moulding plane or template.
I have read that A and B are typically equal. For example, I have a 1 1/2“ sash template, where moulding A can be measured to be 1/2”. If square section B is equal (1/2”) it leaves 1/2” for C - the glazing rebate… perfect. But I doubt that A and B are always equal. And C is unlikely to always be 1/3 the sash depth. But C may always be 1/2”, as glass doesn’t differ much in thickness.

Looking at the Mathieson catalogue from 1900ish, they have sash planes for many sizes of bars available:


IMG_0776.jpeg

Here they show a 2 1/4” glazing bar, probably for a shop front. I can’t believe that the glazing rebate is 2/3“! There must be a standard, which may have been lost in the mists of time.

If anyone knows the answer or where to find out, that would be really helpful. (Hint - the answer is not in mm!)

Steve
 
There's no standard and there are different patterns, local and regional variations, including no mouldings and just bevels instead.
I copied existing and the pattern I used most often was a glazing bar 44x15mm (9/16 x 1 3/4") with 5mm glazing rebate and your A,B,C being about 12.5, 12.5, 19mm. (1/2 x 1 3/4")
The smallest I ever found was 1/2" x 1 1/2" on a little railway cottage window.
Matheson's 3/8 x 1 1/4" seems tiny for external work.
 
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If you look at the construction of a simple rectangular frame - without mouldings or rebates - using mortice and tenons - then the rule of thumb is to divide the thickness into 1/3 ,1/3,1/3. The middle one being the tenon, with the outer 1/3's being where the rebate and moulding is applied. So there is a direct relationship between the size and positioning of central flat area and the tenon.
I'm sure that joiners over the years have tweaked these to suit depending on mortice chisels and moulding planes to hand. and on giving themselves a large enough rebate to bed the glass in with putty ( only really a concern with thinner sashes )

For me the more important visual clue to a window being old, is the actual width of the glazing bar. In many cases they are a lot narrower and far more elegant than their modern equivalents. Some glazing bars I have seen, with "lambs tongue" mouldings, have been narrow enough to have lost the small fillet where the two mouldings would come together - so reducing the width of the bar and stopping it finishing flush with the styles and rails
 
Not really historic as only talking probably 30 years ago but when I used to make quite a few our standard was 5/8", 1/2", 5/8", this allowed for a 1/2" mortise in the flat part in the middle. We used to cut the tenon shoulders just square on the tenoner and because the tenon was in the middle it meant you could flip the rails over so the flat (non moulded side) was always against the splech block..... I'm sure this will make sense to someone!
 
There's no standard and there are different patterns, local and regional variations, including no mouldings and just bevels instead.
I copied existing and the pattern I used most often was a glazing bar 44x15mm (9/16 x 1 3/4") with 5mm glazing rebate and your A,B,C being about 12.5, 12.5, 19mm. (1/2 x 1 3/4")
The smallest I ever found was 1/2" x 1 1/2" on a little railway cottage window.
Matheson's 3/8 x 1 1/4" seems tiny for external work.
I’m sure you are correct, but it’s strange that the tool manufacturers are quite so specific about the size of the stock for the bar. There’s nothing about the sash moulding plane or template that says the bar should be 1.5 inches….

or so I thought …. In fact, the “B” section of the template is exactly 1/2 inch. And is clearly marked on the top, Charles Nurse, 5/8” x 1 1/2“.

IMG_0778.jpeg
 
If you look at the construction of a simple rectangular frame - without mouldings or rebates - using mortice and tenons - then the rule of thumb is to divide the thickness into 1/3 ,1/3,1/3. The middle one being the tenon, with the outer 1/3's being where the rebate and moulding is applied. So there is a direct relationship between the size and positioning of central flat area and the tenon.
I'm sure that joiners over the years have tweaked these to suit depending on mortice chisels and moulding planes to hand. and on giving themselves a large enough rebate to bed the glass in with putty ( only really a concern with thinner sashes )

For me the more important visual clue to a window being old, is the actual width of the glazing bar. In many cases they are a lot narrower and far more elegant than their modern equivalents. Some glazing bars I have seen, with "lambs tongue" mouldings, have been narrow enough to have lost the small fillet where the two mouldings would come together - so reducing the width of the bar and stopping it finishing flush with the styles and rails
I think you hit the nail on the head, it’s a rule of thirds. The central section (I called B) *is* the mortise and tenon position on the bar.

I made a comment earlier that for a 2 1/2“ bar the glazing rebate wouldn’t have been 1/3 of that. I take it back. Thinking of a shop window I was looking at recently, it had perhaps a 10’ by 6’ sheet of plate glass. This would be probably 1/2“ thick and definitely need a significant glazing rebate to hold it.

As for the width of the bars, the standard back then Seems to have been 5/8”, as you say, far more delicate and elegant than the typical 3/4“ bars today.
 
I’m sure you are correct, but it’s strange that the tool manufacturers are quite so specific about the size of the stock for the bar. There’s nothing about the sash moulding plane or template that says the bar should be 1.5 inches….
Thats because they are tool makers trying to sell tools.
or so I thought …. In fact, the “B” section of the template is exactly 1/2 inch. And is clearly marked on the top, Charles Nurse, 5/8” x 1 1/2“.
1/2" is the most common size of mortice chisel and hence of most mortices.
The rule of thirds is just a rough guide for those in doubt.
 
I think you hit the nail on the head, it’s a rule of thirds. The central section (I called B) *is* the mortise and tenon position on the bar.

I made a comment earlier that for a 2 1/2“ bar the glazing rebate wouldn’t have been 1/3 of that. I take it back. Thinking of a shop window I was looking at recently, it had perhaps a 10’ by 6’ sheet of plate glass. This would be probably 1/2“ thick and definitely need a significant glazing rebate to hold it.

As for the width of the bars, the standard back then Seems to have been 5/8”, as you say, far more delicate and elegant than the typical 3/4“ bars today.
5/8" is just one common size. Nothing standard about it and often thinner.
 
what I would suggest here is to make one. without that visual and mental exercise it's hard to imagine how the shapes interlock and the technical problems that were overcome. the size of the flat depends entirely on the fixed size of the mortice chisel and moulding plane everything else is variable. the the depth of the sash is dependant on the size of the case that is where the measurement comefilestores from. typically excess thickness is added to the front(outside) by having a deeper/ shallower rebate. that is what sash fillesters do. that is why there referenced off the moulding side.
 
here's some
 

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notice some lose the flat and are in line with the mould. this presents its own technical problems as the reference face is messed with.
 
next time I go to Leek I'll get some pics of a shopfront to illustrate how the larger sizes are used and what they look like in situ.
 
there's a different approach you will find between machine made stuff and handmade stuff. but as long as the reference face is run at the bottom and mould and rebate are run using the same cutter it's basically the same. the difference in size is placed at the front ready for planing flush
 
even that approach wasn't universal Scottish makers used a glass check plane not unlike a tongue plane for sinking both rebates together.
 
Hi

I am doing some research to discover the dimensions of historical sash window bars. I thought perhaps there might be an old joiner about who has repaired original windows and knows. In particular, I wondered if there was a standard size for the glazing rebate.

I have scoured all the old texts, Ellis, Hasluck etc and none of them really seem to say.

The dimensions I’m looking for are A, B and C below.View attachment 164801
In general I know A+B+C. It’s given by the size of the moulding plane or template.
I have read that A and B are typically equal. For example, I have a 1 1/2“ sash template, where moulding A can be measured to be 1/2”. If square section B is equal (1/2”) it leaves 1/2” for C - the glazing rebate… perfect. But I doubt that A and B are always equal. And C is unlikely to always be 1/3 the sash depth. But C may always be 1/2”, as glass doesn’t differ much in thickness.

Looking at the Mathieson catalogue from 1900ish, they have sash planes for many sizes of bars available:


View attachment 164804
Here they show a 2 1/4” glazing bar, probably for a shop front. I can’t believe that the glazing rebate is 2/3“! There must be a standard, which may have been lost in the mists of time.

If anyone knows the answer or where to find out, that would be really helpful. (Hint - the answer is not in mm!)

Steve
Hello Steve, do you do Instagram? you might like to talk to @arnold_richard on there or @richarnold here, he not only has an extensive selection of the original tools for doing this but has used them many times to show how they worked.
Cheers, Andy
 
If you look at the construction of a simple rectangular frame - without mouldings or rebates - using mortice and tenons - then the rule of thumb is to divide the thickness into 1/3 ,1/3,1/3. The middle one being the tenon, with the outer 1/3's being where the rebate and moulding is applied. So there is a direct relationship between the size and positioning of central flat area and the tenon.
I'm sure that joiners over the years have tweaked these to suit depending on mortice chisels and moulding planes to hand. and on giving themselves a large enough rebate to bed the glass in with putty ( only really a concern with thinner sashes )

For me the more important visual clue to a window being old, is the actual width of the glazing bar. In many cases they are a lot narrower and far more elegant than their modern equivalents. Some glazing bars I have seen, with "lambs tongue" mouldings, have been narrow enough to have lost the small fillet where the two mouldings would come together - so reducing the width of the bar and stopping it finishing flush with the styles and rails
Yes, you can get a mitre templet for the ones that are missing the flat and this is going to put the cat amongst the pigeons.

Here's my little set of planes which I use for windows and the matching templets for them, all are stamped No.178 5/8 and the pair of planes have No.1 and No.2 on them as you would expect. Each plane has its own matching templet form the pair. Plane No.1 fits one templet only and plane No.2 fits the other templet only .

Both planes are No.178 and one makes thicker glazing bars with the flat fillet and the other makes pointy, thin glazing bars.


$_57-1.JPG
$_57.JPG
$_57-3.JPG
$_57-2.JPG


And for a bit of fun, here's my scribing plane too.Bought off the bay of flea a while back, shame it doesn't fit the sash planes properly though.

$_12.JPG
 
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