Making sash windows?

Discussion in 'Carpenters' Talk' started by rich6757, Feb 9, 2019.

  1. rich6757

    rich6757 New Member

    Anyone here made their own sash windows?

    I need to replace 2 large triple sashes, currently single glazed, with double glazed wood sashes.

    Quotes are all over £9000 for 2 windows.

    I've read a few blogs and been looking at a lot of posts on some other forums about making sash windows.

    I have time and the space to do it.

    Eventually I will need to replace 4x triple sashes and 4x large bays (estimated total cost to have made and installed £50k!). So even a large investment in decent machinery would not be an issue.

    It may well be the case that I can recover some parts of the existing window frame, but the cills and bottoms of the outer linings are all shot. So for now I am assuming I will be making completely new windows.

    So looking for advice, tips and hopefully constructive critisism of my plans!

  2. sospan

    sospan Well-Known Member

    rich6757 likes this.
  3. rogerk101

    rogerk101 Well-Known Member

    I've made my own sash double glazed windows before but I wouldn't dream of trying it with the pulleys and lead weights. Go for the balanced spring approach. Buy your spring set factory set to the exact final weight of the sash.
  4. rich6757

    rich6757 New Member

  5. rich6757

    rich6757 New Member

    Hi Roger,

    Not a fan of springs. We have some of those. A lot have packed up. Any particular reason you don't like pulleys and weights?
  6. Mr Rusty

    Mr Rusty Well-Known Member

    I see you've read my thread - It can be done!. However 4 x triple and 4 x bays is huge. I made 7 standard doubles without glazing bars and I reckon it was somewhere around 200 hours work in total inc painting.

    My suggestions -

    Plan well - all the fittings seals etc are available - I used reddiseals for most stuff.
    Buy some good tools - In addition to all the standard stuff, you need a good router table. I used a domino 700 for joints, bought a cheap thicknesser, and a band saw for ripping some of the sections.
    Work accurately. I anally tried to always set the router table to 0.1mm, but reckon I was achieving about +/- 0.25mm most of the time. When assembled my internal frame dims were virtually all +/- 0.5mm , the odd one +/- 1mm.

    Accoya has proved to be totally stable. The first window is now in its second winter and hasn't shifted a smidgen. Not cheap - about the same as oak - circa £2K m3
  7. Mr Rusty

    Mr Rusty Well-Known Member

    ....and be realistic about your experience and capability. This is not a beginner project no matter how good the tools you have !! :p:p
    rich6757 likes this.
  8. dobbie

    dobbie Well-Known Member

    All the timber sections that you require to make the boxes and the sashes are available to buy from good timber merchants.
    You do not need to machine them from scratch.
  9. KIAB

    KIAB Well-Known Member

  10. rich6757

    rich6757 New Member

    Hi Rusty, Thanks for the encouragement!

    With I bit of luck I might have a Felder Combi machine and a Multico mortiser. I have a router and bandsaw. Also have stuff to measure things accurately.

    From what I got quoted, a professional is taking 35 hours to make a triple sash, so that's not far off what you managed. Your windows look great.

    I have costings for Accoya and all the fittings etc. Just making some decisions on rail/style size. Originals are 40mm but I think I will go to 57mm and use proper width DGUs. I'm not sure I trust slim units.

    I plan to prototype a window or two first, just to get the process down. I will probably also just replace a couple of sashes on a single window we have, that has a good frame, first.

    I have read the classic joinery books and a load of blogs and forum posts. I have the Mumford drawings and I am doing my own in sketchup.

    A good blog is

    I've been on readyseals and mighton and seen their stuff.

    Some open questions are, apart from full width vs slim DGU's are the use of tapes, low modulus silicon and dry epdm for glazing. Seems there is no best solution, just what people get used to doing.

    Your use of dominos is interesting and obviously a huge time saver. You are reliant 100% on glue and I have no idea how it will perform in 10-20 years?

    I also noticed you bought in a ready made cil? Any reason for not using Accoya? I'm not sure if there are large enough stock sizes for big cils?

    Did you fit the pulley stiles to the cil with a notch in the cil and screws up from underneath or the trad method of a tapered notch and wedges?

    Hope you don't mind me picking your brains!

    When I get started I will try and document the process and my mistakes as a lot of people seem to be interested in making sash windows.
  11. rich6757

    rich6757 New Member

    Thanks for the link, little steep though. 2x to 3x the price of stock sections.

    For example 100x25mm accoya is about £6.60 a metre. An 80mmx38mm profile is £21 to £29 per metre. That's going to add up making 8 triple sash windows!
  12. KIAB

    KIAB Well-Known Member

    Was just an example, if you have the machinery, then machine your own, disadvantage is the higher cost of timber, for stability,longer lifespan,etc, accoya is hard to better.
  13. rich6757

    rich6757 New Member

    That's the plan and who doesn't like some new machinery!
  14. Mr Rusty

    Mr Rusty Well-Known Member

    I looked at ready made profiles and couldn't find anything that worked for 24mm dgu in the way I wanted to fit them.

    I didn't buy a ready made cill. They were machined from sawn utile. Again so I had the profile I wanted. Not sure why I didn't use accoya for the cill as well....

    Yes pulley Stiles into notches in cill with 2 dominos up from underneath. All glued with Pu glue.
  15. rich6757

    rich6757 New Member

    Hi Rusty, when you made the cill, did you use a cill block on a moulder or improvise with a router table and a dado/planer bit?
  16. Mr Rusty

    Mr Rusty Well-Known Member

    For the cills I just slotted the face on the router table and then took off the chamfers with a hand power planer. Tidied up with a hand plane. I have a top end blue Bosch which can take off up to 4mm on a pass, although I didn't take that much off at once.
    jacobite likes this.
  17. JustPhil

    JustPhil Active Member

    You have my vote, go for it, make those windows! Why buy something when the money can be spent instead on the tools to make it? So long as you have the time...

    I’d always favour joinery and glue over mechanical fixings (screws) for the long term. Just make sure you’re using the right wood glue for the job - waterproof. I haven’t checked but I’m thinking titebond 3 or similar.
  18. Mr Rusty

    Mr Rusty Well-Known Member

    For Accoya you basically have two choices - PU or Epoxy.

    +1. My windows used zero screws apart from mounting internal furniture.
    Last edited: Feb 10, 2019
  19. rich6757

    rich6757 New Member

    So assuming that a modern PU glue is stronger than the wood itself, how does the strength of Accoya compare to a real tree species such as Sapele?
  20. Mr Rusty

    Mr Rusty Well-Known Member

    I think the biggest difference is the stability of Accoya. According to wood database, the tangential/radial shrinkage of Sapele between wet and kiln dried is 7.2/4.8% whereas Accoya is 1.5/0.7%. In my book that stability means that tightly glued joints stay tightly glued.

    The weakest joint in a sash window is going to be the upper sash stile to meeting rail. This is why the top sash has horns - to increase the amount of material below joint. The joint is in shear, so whether it is a tenon or a domino, it's going to be strong enough to carry the weight of the DG unit. Provided the DG is tightly supported in the rebate there should never be any lozenging of the frame to stress the joints.
    KIAB likes this.

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