Sash Windows

[monster]

I’m in the midst of making 3 sash windows out of rough sawn Accoya, to a tradition design - i’m basically copying off some existing so I’m not using any modern methods of draught proofing.

I’ve made the 3 sash box frames and I’m about to start preparing the timber for the sashes.

My questions are around optimal sizing for the sashes such that they will slide smoothly and easily within the frame without binding and conversely don’t rattle about to much.

So what should I allow around the sashes, both in the sizing between the beads and then also in overall width of the sashes?

 

[monster]

A few pics of one of the finished frames.

 

[Jacob]

say 2mm clearance on each edge and 1mm on each face against parting slip/staff bead of front lining. i.e. 4mm / 2mm overall
They need to move freely and with the right weights so that the top and bottom edges will be firmly up against the top/bottom of the frame.
The meeting rails benefit from fine adjustment so that the catch pulls them together to nip the parting bead a touch so they can't rattle about.

 

[monster]

Thanks for that Jacob, I have made a sash window once before, it was may first real project - but I have forgotten what tolerance i used - and whatever I used is a little tight between the beads for my liking, so just wanted to get that right this time.

 

[Doug71]

You can hide the seals behind the sash stiles so they are not seen if you want to keep the traditional look, it does stop the rattles and can help them slide easier.

You might have already seen it but there are examples in this thread

https://www.ukworkshop.co.uk/threads/sash-seals-on-the-sash-rails-not-the-frame.128392/

 

[mr rusty]

I made a house full of sash windows in accoya a while back and found I could work to very tight tolerances. Accoya doesn't move about, and 3 years later they have stayed 100% stable. Mine were not traditional - based on design of one of the big suppliers who conveniently post CAD drawings - designed for 24mm DGU and dry glazed with internal beads.

What paint you going to use? I sprayed Teknos aqua primer and aquatop with a HVLP sprayer and it went on a treat.

pic is a trial fit - my meeting rail seal was a double brush - as you see very small gap to close.

 

[Ollie78]

Just make them a bit big and shoot them in for the width and height.
For not having draught proofing 2mm is probably enough for thickness.

However, not having draught proofing is a bit of an oversight, seeing as you are making them from scratch you might as well make them as good as you can.
Even if you just do it on meeting rail and staff bead. If done right it's virtually invisible.

Ollie

 

[Jacob]

Just make them a bit big and shoot them in for the width and height.
For not having draught proofing 2mm is probably enough for thickness.

However, not having draught proofing is a bit of an oversight, seeing as you are making them from scratch you might as well make them as good as you can.
Even if you just do it on meeting rail and staff bead. If done right it's virtually invisible.

Ollie

If you did do draught proof I'd give it a miss on the meeting rails and the bottom rail as these allow condensation to drain away. Otherwise you are creating a water trap.
I never bothered with draught proofing - if they are a good fit you don't get draughts, over and above the trickle you need to keep things dry and enough fresh air in the room.

 

[Ollie78]

Jacob.
It's a matter of opinion I guess, but because you can never seal the corner where the meeting rails meet the parting bead this is usually enough for trickle ventilation.
I mostly do slim DGUs which do cut down the condensation a good amount.

To my mind it is better to be able to start from a draught free position and control it from there by opening the window for 5 minutes in the morning for example.

A draught you can't control is more annoying than one you can.
The other advantage of parting bead and staff bead draughtproofing is it gives a nice smooth motion with much less chance of pinching with seasonal movement, gives you a larger tolerance and makes the windows feel nicer to operate, also doesn't rub the paint off.

Ollie

 

[Jacob]

Jacob.
It's a matter of opinion I guess, but because you can never seal the corner where the meeting rails meet the parting bead this is usually enough for trickle ventilation.
I mostly do slim DGUs which do cut down the condensation a good amount.

To my mind it is better to be able to start from a draught free position and control it from there by opening the window for 5 minutes in the morning for example.

A draught you can't control is more annoying than one you can.
The other advantage of parting bead and staff bead draughtproofing is it gives a nice smooth motion with much less chance of pinching with seasonal movement, gives you a larger tolerance and makes the windows feel nicer to operate, also doesn't rub the paint off.

Ollie

I only did period restoration stuff which meant exact copying of Victorian and Georgian originals, so DG and draught proofing were out anyway. But properly set up they weren't particularly draughty at all. Sashes got a reputation for draughts but that was because some of them were 100 years old or more with very little maintenance. Nice and new there was no prob.

 

[Ollie78]

I only did period restoration stuff which meant exact copying of Victorian and Georgian originals, so DG and draught proofing were out anyway. But properly set up they weren't particularly draughty at all. Sashes got a reputation for draughts but that was because some of them were 100 years old or more with very little maintenance. Nice and new there was no prob.

I end up often doing a sort of hybrid where they must look like georgean but perform much better, not always an easy task. Often repairing the boxes but putting in new upgraded sashes.
I actually quite enjoy grade 1 listed stuff on occassion where you can`t do anything but exact replicas, sometimes they wont even let you replace them but repair the existing disasters with invisible splices and matching timber, I never really understood the point of this, more work for a very similar result.

Looks like monster is doing a fine job anyway.

Ollie

 

[monster]

Mr Rusty - I've used Sadolin Superdec on my windows before and still have half a tin left, so I'm planning on using that - unless someone tells me its not compatible with Accoya... I'll brush it on rather than spray.

I understand the arguments for draught proofing, but don't really see the point in this instance of doing these 3 windows when the remaining 50 of the existing old original Ewardian windows are all single glazed and without any draught proofing. I'm a bit of a believer of a well ventilated house being a healthier place to be - and that was before the covids lol. It seems to be a naturally warm house anyway - I was surprised how warm it was when we first moved in, I was expecting it to be a cold house, but its not - seems to be naturally much warmer than the last place we had.

I do however take Ollie's point on board, and see it as a very sensible one, that a good starting point is to make everything draught proof and then introduce the ventilation in a controlled manner to suit! - and where I to be making a complete set of windows for a house I would probably then take that approach. In this instance though, I want keep them all the same and looking as close to original as possible in order to match all the existing.

 

[mr rusty]

Mr Rusty - I've used Sadolin Superdec on my windows before and still have half a tin left, so I'm planning on using that - unless someone tells me its not compatible with Accoya... I'll brush it on rather than spray.

I understand the arguments for draught proofing, but don't really see the point in this instance of doing these 3 windows when the remaining 50 of the existing old original Ewardian windows are all single glazed and without any draught proofing. I'm a bit of a believer of a well ventilated house being a healthier place to be - and that was before the covids lol. It seems to be a naturally warm house anyway - I was surprised how warm it was when we first moved in, I was expecting it to be a cold house, but its not - seems to be naturally much warmer than the last place we had.

I do however take Ollie's point on board, and see it as a very sensible one, that a good starting point is to make everything draught proof and then introduce the ventilation in a controlled manner to suit! - and where I to be making a complete set of windows for a house I would probably then take that approach. In this instance though, I want keep them all the same and looking as close to original as possible in order to match all the existing.

I'm not proselytising - just, as a DIYer, showing what I did. Take your point about ventilation - our windows are often cracked open which kind of makes the draught proofing irrelevant (until it's blowing a hooley and you want to batten down). I chose Teknos purely because I had read that pro window makers were using it on accoya - I figured there was an element of "tried and tested".

I love sash windows. Before I made mine I researched loads, and found much contradictory information - for example, in an Irish publication I found "the weight pockets are usually on the inner lining" - (where I put mine) - but most traditional English windows have the pockets in the stile? why? seems a bit daft to me to put it on the bearing and more-exposed-to-the-weather surface.

In the end, I decided, although I wanted to respect tradition, I would go for a latest-technology approach whilst at the same time trying to keep a reasonably traditional appearance.

 

[Jacob]

I'm not proselytising - just, as a DIYer, showing what I did. Take your point about ventilation - our windows are often cracked open which kind of makes the draught proofing irrelevant (until it's blowing a hooley and you want to batten down). I chose Teknos purely because I had read that pro window makers were using it on accoya - I figured there was an element of "tried and tested".

I love sash windows. Before I made mine I researched loads, and found much contradictory information - for example, in an Irish publication I found "the weight pockets are usually on the inner lining" - (where I put mine) - but most traditional English windows have the pockets in the stile? why? seems a bit daft to me to put it on the bearing and more-exposed-to-the-weather surface.

In the end, I decided, although I wanted to respect tradition, I would go for a latest-technology approach whilst at the same time trying to keep a reasonably traditional appearance.

I've done them in the lining - copying the originals in a posh house in Ireland. They were big top quality sashes from about 1815.
Having pockets on the inside lining makes some maintenance easier (you don't have to take the pulley stiles and sashes out to get at the weights) but it's much more difficult to do neatly. They are out of sight in the pulley style if placed behind the bottom sash but I've also seen them sited in the middle of the pulley stile, for no obvious reason.

 

[monster]

Finished these three sash windows now, enjoyed making them, they are an exact copy of the existing windows in the house.

Accoya was very nice to work with, my only slight criticism of it is that it’s quite brittle, but I’m sure all the positives far outweigh that factor.

just got to paint, glaze and fit them now!

some pics

 

[monster]

So one question I’ve got for the knowledgable or even those wishing to speculate - what is the thinking on why the top rail of the box sash frame is so deep???

It leaves a big space above the window that I think looks really odd and aesthetically is not what I would choose to have designed at all - virtually every original window throughout the house is made like this. The house is Edwardian and was built in 1906.

My only thinking is it’s an ideal space for a blind to be rolled or furled up into, but would they really have designed windows with soft furnishings in mind....

Anyone else seen this before or have any thoughts - I’d love to hear them as it’s had me wondering since I bought the place?

Here are a couple of pics of original existing windows in a bay with said large gap above.

 

[mr rusty]

great job!. A question on your M&T's. It doesn't look quite like a wedged tenon? what did you do? When I made mine I considered the traditional approach but 1) I couldn't face cutting 64 haunched tenons (for 8 windows), and 2) I though that accoya would be too brittle for wedges and would break, (did they) so I used dominos. I bought the domino specifically for this job and "lost" the cost into the saving I made making my own windows

I agree, accoya is nice to use but is brittle.

 

[Jacob]

1906 is getting late for sashes they were starting to go out of fashion in favour of vaguely "Queen Anne" style casements.
Never seen anything like yours. I guess just an architectural whimsy. Might make more sense from outside?
No room there for curtain rails - would be good for roman blinds - any sign of screw holes for fittings?

 

[monster]

great job!. A question on your M&T's. It doesn't look quite like a wedged tenon? what did you do? When I made mine I considered the traditional approach but 1) I couldn't face cutting 64 haunched tenons (for 8 windows), and 2) I though that accoya would be too brittle for wedges and would break, (did they) so I used dominos. I bought the domino specifically for this job and "lost" the cost into the saving I made making my own windows

I agree, accoya is nice to use but is brittle.

Hi Rusty, I did use wedged mortice and tenons for each joint except for the top rail of the bottom sash which is still a mortice and tenon but that one is dowelled rather than wedged as the amount of materiel above it is so marginal that it would probably break out as you knocked the wedge in - this is exactly how my original existing windows were done - I merely copied of them.

I have a domino and love using it and understand why if you are doing a large number you’d want to use it, but for some reason it didn’t feel right for me to use on this job, maybe it’s cos I was copying the originals and felt I should be as faithful as possible to the original design!

 

[monster]

1906 is getting late for sashes they were starting to go out of fashion in favour of vaguely "Queen Anne" style casements.
Never seen anything like yours. I guess just an architectural whimsy. Might make more sense from outside?
No room there for curtain rails - would be good for roman blinds - any sign of screw holes for fittings?

Jacob, yes, most of the other houses around here from that era have casement windows - all the houses are very different though and were built by different architects of the day - although all built around the same time!

On the outside - ie behind the really deep top rail it’s finished with - I think they call them something like a rubbed brick header.... not sure if that could have anything to do with it, here is a pic of outside.

It would be perfect for blinds but the boss wants curtains - only option I can see there though is for the track to attach to the top of the architrave though for that to work.