# Making Box Sashes, wood choice etc



## Flat Pat (27 Jun 2020)

I recently replaced a rotted box sash sill in my house using hand tools. It went well so I've decided, perhaps naively, to go further as there are a lot of them requiring new sills and sashes. The wife wants new double glazing all round but keep the traditional look, everything is original single glazed turn of the century and very lovely. It would cost a fortune to buy in.

Since doing the sill, I have an Axminster table saw, a planer/thicknesser and a router. The plan is, after first making some jigs/sleds, to try a small test sash, see if I can't get reasonable results and understand the construction methods and procedure. If successful proceed to full size and start replacing some of the sashes that have rotted in the existing boxes, but use double glazed panels (and heavier weights), if that's possible given the existing sash thickness. If THAT goes OK I'll try to build a full window and start replacing/refurb bit by bit.

We had some casement windows fitted in a loft dorma a few years ago - these were sapele and they move a lot. Had to plane them because the sashes jammed. With that in mind wood choice is going to be very important, I'm thinking of using Woodex RedGrandis or Woodex Softwood if I go all in DIY. Maybe Sapele or Cedar for sills? But I have zero experience with choosing timber, this is purely from researching online (including here). How is woodex to work with for a noob?

I want to go traditional as much as possible and use linseed paint for finish. Will this affect wood choice?

Am I mad to think this is even doable?


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## Trevanion (27 Jun 2020)

Flat Pat":3r9ojht3 said:


> Am I mad to think this is even doable?



Nope, not mad... a little ambitious perhaps 

There's no reason at all that you can't make the sashes yourself even with the most basic of tools, You've already got the main ones I would suggest with the exception of a morticer of some kind but that's purely optional as you can do mortices fairly easily with a router or by hand. Once we've sussed exactly what you're going for I can probably suggest some ideas on how to do the job as there are many ways to skin a boxed sash window.

As for making the sashes fit the existing boxes with double glazing fitted, that all depends on how exactly you want them to look, there's probably a good chance you'll struggle to get a like-for-like looking sash to fit a double glazed unit but that all depends on the make-up of the orignal sashes, got any pictures?

Seals are something worth considering, I like to use Aquamac 21 on the top and bottom of the sash and then Deventer flipper seals on the sashes between the sash, box, and parting bead rather than using a plastic parting bead which helps them run smoothly and allow a little for any movement whatsoever.







Heavier weights are definitely possible, some people will lead-jacket the original weights with roofing lead which is a bit of a cowboy way of doing it, some others will buy square lead weights with a hole bored down the centre and others will have square steel weights with a nut welded on top.

I personally wouldn't use RedGrandis simply because I've been told not to touch it with a bargepole by experienced people whose judgment I trust. Quality, stability, and delamination issues were brought up, which was very concerning, plus the fact it's at a pricepoint where you may as well opt for Accoya at a smidge more. To be honest, using any laminated timber on sliding sashes is a little bit of a waste of time and money because the sections are so small there won't be too much instability issues, if you're thinking of Woodex softwood you may as well just go for regular softwood at a fraction of the cost although I wouldn't suggest it because the joinery softwood of today pales in comparison to the softwood they had 100+ years ago which fanatical traditional sash people rave on about "_Our old sashes were made from softwood and lasted a hundred years therefore the new softwood will too..._" "Yeah, but the old softwood had a hundred growth rings in an inch of timber and the new stuff has like two or three tops!" 

Accoya would be my first choice but Sapele would be my close second.


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## Flat Pat (27 Jun 2020)

Thanks, this is great info. Understood re woodex, I was wondering about the laminations. I'd want to avoid plain softwood precisely for the reasons you give, I have some old pitch pine rafters from the loft conversion and the ring density is huge (and they are pungent with resin). Its incomparable to new stuff.

How about cedar? or Idigbo? (we have french doors made of cedar and seem to be impervious).

One of the front bay windows:





At the rear:


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## Flat Pat (27 Jun 2020)

I can see a mortiser would be handy. Was hoping I could cut the tenons on the saw and the mortice by hand (I do like working with hand tools, but might be different when having to make 8 or more mortices them per window).

I would like to use seals but would like them as hidden as possible. What's best type for noise reduction?


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## Trevanion (27 Jun 2020)

Flat Pat":clnrqwqr said:


> How about cedar? or Idigbo? (we have french doors made of cedar and seem to be impervious).



Cedar is ludicrously expensive and again, you may as well opt for Accoya at that point and have the proper peace of mind that it'll never move or rot.

Apparently it's getting very difficult to get a hold of decent stocks of Idigbo now and it may just disappear from the market completely fairly soon. It's a very durable timber but it's an absolute pig to work with especially when morticing.

The biggest difference to noise will be from the double glazing than anything else, noise reduction from seals will be pretty marginal.


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## Flat Pat (27 Jun 2020)

OK, sounds like Accoya is the way to go.


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## Doug71 (27 Jun 2020)

I would go with Accoya, you won't need much for the sashes. Cedar is a bit soft (surprised you have french doors made of it). I always think of Idigbo as just a light coloured Sapele often used to imitate Oak if you don't want to pay for Oak.

Like Trevanion I prefer to put the seals on the sashes where they are not seen rather then the brush type seals you often see on the staff beads etc.

To keep the look for the double glazing you will most likely need to use the Heritage stuff which is expensive and has had bad press about longevity but might be better now.

Never tried linseed paint myself, sounds a bit of a faff.


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## Flat Pat (27 Jun 2020)

From what I've read about it linseed paint is easier to maintain. Just re-oil once it goes matte. I'm sick of plastic paint that cracks and flakes.


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## Artiglio (27 Jun 2020)

Following Trevanions comment on timber quality, this was used for a joist in 1907, i’d guess it was about 200 plus years old when felled. Smelt lovely when i cut it.
I’ve kept it to keep reminding the conservation officer that their view of what constitutes like for like replacement is not a practical reality when it comes to timber availablity.


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## Flat Pat (27 Jun 2020)

Look similar density to the ones from my house c1913. I cut one up for firewood (it has some rot), but wish I hadn't now! Still have a few 3 foot pieces left one of which I put through the thicknesser to test it and the surface was nice.


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## Flat Pat (27 Jun 2020)

Question: can I make mortices with my plunge router, making the tenon narrower to clear the rounded ends of the mortice?


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## thetyreman (27 Jun 2020)

you could use pitch pine if you can get hold of any, I've seen old pitch pine doors going for cheap on ebay, 

what about redwood pine?

I'd be using linseed oil paint as well! from everything I have seen nothing comes close in terms of durability, and it's 100% natural, no nasty chemicals.


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## Doug71 (27 Jun 2020)

Flat Pat":1jqoeh9x said:


> Question: can I make mortices with my plunge router, making the tenon narrower to clear the rounded ends of the mortice?



The normal thing to do is chisel the round ends square.


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## Flat Pat (27 Jun 2020)

Doug71":22s9xgwb said:


> Flat Pat":22s9xgwb said:
> 
> 
> > Question: can I make mortices with my plunge router, making the tenon narrower to clear the rounded ends of the mortice?
> ...



Is it structurally better for a sash frame to do that? Thinking that the glass panel is adding a lot of rigidity anyway.


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## LBCarpentry (27 Jun 2020)

We do tonnes of this. Remake sash’s in a completely traditional style that incorporate a double glazed unit. 

Ask your local glass supplier about “heritage” glass units. A 12mm overall DG unit with an 8mm sightline. Designed to be traditionally puttied into the sash. No more stick on glazing bars hoorah. 

I’ve used woodex softwood for loads of windows including some of my own. It’s bloody lovely stuff to work with but as everyone says Accoya is the top dog. 

On a closely related topic I started thinking this week : “I wonder if anyone is making box sash window frames using tricoya??” Would be a piece of cake surely! Except for the cill of course that would have to be solid.


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## Trevanion (27 Jun 2020)

LBCarpentry":huqr7hii said:


> On a closely related topic I started thinking this week : “I wonder if anyone is making box sash window frames using tricoya??” Would be a piece of cake surely! Except for the cill of course that would have to be solid.



I know someone who does that and doesn't even mention to the customer that their window frames are basically made from MDF. I wouldn't do it simply out of principle and I've seen Tricoya do funny stuff before and I wouldn't risk it, also there's barely anything in the price.


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## Flat Pat (27 Jun 2020)

LBCarpentry":h8rcn9j5 said:


> We do tonnes of this. Remake sash’s in a completely traditional style that incorporate a double glazed unit.
> 
> Ask your local glass supplier about “heritage” glass units. A 12mm overall DG unit with an 8mm sightline. Designed to be traditionally puttied into the sash. No more stick on glazing bars hoorah.
> 
> ...



This forum is great! Thanks for all the advice so far.

I’ll ask the glass supplier about the heritage stuff. Thx.

Any opinion on traditional linseed paint? I’d watched some YT videos by Peter Ward about it. Like the idea if what he says is true.


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## deema (27 Jun 2020)

No body’s suggested Douglas Fir. Knot free, stable, very little expansion and contraction, takes paint well and easy to work.


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## AndyT (28 Jun 2020)

There's a long and lively discussion about linseed oil paint here

trying-linseed-paint-141-68-for-1-litre-t107300.html

Probably a few others too.


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## LBCarpentry (28 Jun 2020)

deema":1fi7prl2 said:


> No body’s suggested Douglas Fir. Knot free, stable, very little expansion and contraction, takes paint well and easy to work.



Except - it’s the opposite of those things isn’t it. Look, I used Douglas fir for years. 10 year ago it was “good” but I have witnessed its demise whilst the price sky rocketed. Not a viable option for much anymore.


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## deema (28 Jun 2020)

Errrrm, not in my experience it’s exactly like that when bought from a good stockist.
Sapele can have interlocked grain, can be very difficult to work especially with hand tools. Moves a lot, and needs more paint prep. But is a good wood for doors and windows.


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## Doug71 (28 Jun 2020)

Flat Pat":1ji1xlve said:


> Doug71":1ji1xlve said:
> 
> 
> > Flat Pat":1ji1xlve said:
> ...



You need as much tenon as possible for strength, especially if you go down the double glazed route. The sash sections can be quite small and you are now doubling the weight of the glass.

Once you cut the haunches off the tenons and groove out for the sash cords there isn't much tenon left so you need to make the most of what you have.

I almost used some Tricoya for the fronts of a window once when I ran short of Accoya, I couldn't bring myself to do it but couldn't think of a good reason why you shouldn't use it in that situation?


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## Flat Pat (28 Jun 2020)

Doug71":291xwmd2 said:


> You need as much tenon as possible for strength, especially if you go down the double glazed route. The sash sections can be quite small and you are now doubling the weight of the glass.
> 
> Once you cut the haunches off the tenons and groove out for the sash cords there isn't much tenon left so you need to make the most of what you have.
> 
> I almost used some Tricoya for the fronts of a window once when I ran short of Accoya, I couldn't bring myself to do it but couldn't think of a good reason why you shouldn't use it in that situation?



(googles tricoya)...

Ah yes the sash grooves, makes sense now.

I've been watching some videos of sashes being made and one of the methods involved having wider mortices that are then wedged. This seems like it might be a more noob friendly method - strong but less accuracy needed?


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## Trevanion (28 Jun 2020)

deema":1516hzkb said:


> No body’s suggested Douglas Fir. Knot free, stable, very little expansion and contraction, takes paint well and easy to work.



I agree with LB, I've always had a pretty poor experience with the doug fir I've received over the years, coarse grained, full of knots and resin pockets, massive amounts of movement and twisting, and to top it off minuscule spots of mould in the timber would grow and show up through the paint like a leopard print (Not my work, but I've seen it on someone else's work).

Of course, just with any timber it's all down to the quality of the trees, some will make cracking, usable timber and some are really only fit for firewood.



Flat Pat":1516hzkb said:


> Any opinion on traditional linseed paint? I’d watched some YT videos by Peter Ward about it. Like the idea if what he says is true.



It's a load of nonsensical faff in my opinion, buy *good quality* water-based paint and you'll get similar long-lasting results, buy dung paint get dung results.


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## LBCarpentry (28 Jun 2020)

Bradite One Can has been my true love for the past few months. “One can to rule them all” I scream as I open the tin. Prime, stain block, topcoat all in one. I know what your thinking but give it a go. 

I dropped a few drips into my kitchen sink accidentally a few weeks ago and damned if I can get it off!


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## Flat Pat (29 Jun 2020)

LBCarpentry":3h621b61 said:


> Bradite One Can has been my true love for the past few months. “One can to rule them all” I scream as I open the tin. Prime, stain block, topcoat all in one. I know what your thinking but give it a go.
> 
> I dropped a few drips into my kitchen sink accidentally a few weeks ago and damned if I can get it off!



I'll bear that stuff in mind if I chicken out of going the linseed route


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## thomashenry (7 Jul 2020)

What reason would there be for NOT using linseed paint?


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## Trevanion (7 Jul 2020)

thomashenry":x05gf4sz said:


> What reason would there be for NOT using linseed paint?



I've got a life to live and I'd rather not spend it watching paint dry for weeks :lol:


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## thomashenry (7 Jul 2020)

It really doesn't take THAT long.


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## thomashenry (7 Jul 2020)

Good on you for attempting this. I would resist the wife's desires for DG, though I appreciate you've got to let them win sometimes. I've re-made several sash boxes in my house, where the cills and lower reaches of the stiles were rotten. All the sashes were more or less ok though... I stripped them, reglued, repaired where needed and re-painted (linseed paint ). In my experience it's fairly uncommon for the sashes to rot beyond repair. The top sash especially - I've never seen rotton top sash.


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## Flat Pat (7 Jul 2020)

thomashenry":3knwxm3w said:


> Good on you for attempting this. I would resist the wife's desires for DG, though I appreciate you've got to let them win sometimes. I've re-made several sash boxes in my house, where the cills and lower reaches of the stiles were rotten. All the sashes were more or less ok though... I stripped them, reglued, repaired where needed and re-painted (linseed paint ). In my experience it's fairly uncommon for the sashes to rot beyond repair. The top sash especially - I've never seen rotton top sash.



If it was up to me, yeah I'd keep the single glazing.

Good point about refurb vs full rebuild. They're absolutely covered in layers of plastic paint and the thought of trying to strip them mortifies me. It likely sensible for the upper sashes and inner box and surround though and 'refurbing' would keep me out of any building regs grief, I hope.

I got a sample of Accoya the other day. Had a legend printed on it saying measure, submerge in water for any length of time then re-measure. Tbh it feels sort of non-wood like. Almost like a lightweight ceramic of sort, or maybe somewhere between.


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## RogerS (7 Jul 2020)

Trevanion":2f1z9sn8 said:


> ....
> It's a load of nonsensical faff in my opinion, buy *good quality* water-based paint and you'll get similar long-lasting results, buy dung paint get dung results.



LOL...we'll have to agree to disagree. When my LOP starts to look a little bit in need of attention, just a quick rub down with linseed oil soap and we're good to go. Beats sanding down...again..and again !


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## RogerS (7 Jul 2020)

Flat Pat":3eaq8vcx said:


> thomashenry":3eaq8vcx said:
> 
> 
> > Good on you for attempting this. I would resist the wife's desires for DG, though I appreciate you've got to let them win sometimes. I've re-made several sash boxes in my house, where the cills and lower reaches of the stiles were rotten. All the sashes were more or less ok though... I stripped them, reglued, repaired where needed and re-painted (linseed paint ). In my experience it's fairly uncommon for the sashes to rot beyond repair. The top sash especially - I've never seen rotton top sash.
> ...



I agreed with most of what's been said. The only comments I'd make are that if the windows are well-maintained etc then there is no need to go down the expensive Accoya route. (I'm starting to sound like Jacob)

Also, double-glazing in a traditional single paned sash window...OK. Double glazing in a multiple-paned sash window....especially in an older property = NAFF. Georgian bars stuck in between the panes looks awful IMO. Plus they never get the glazing bars/Georgian bars down to those really beautiful narrow glazing bars in a true Georgian sash window.


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## Trevanion (8 Jul 2020)

RogerS":11dqzw7s said:


> Also, double-glazing in a traditional single paned sash window...OK. Double glazing in a multiple-paned sash window....especially in an older property = NAFF. Georgian bars stuck in between the panes looks awful IMO. Plus they never get the glazing bars/Georgian bars down to those really beautiful narrow glazing bars in a true Georgian sash window.



That's something we can agree on Roger! Had an inquiry about triple glazed boxed sash windows with Georgian bars. A 44mm unit Brings your sash thickness up to a real meaty 75mm and the boxes would have to be something like 8" deep.







Well-to-do Londoners reading too much Grand Designs Weekly :roll: :lol: 

I don't do too much _proper_ morticed/mitred glazing bar work anymore but I do a lot of stick-on but I do like to think I do it neater than most others who tend to stick on both sides, the internal side on mine are cut in tightly with the same scriber knives as the moulding then glued and screwed in place from inside the rebate so when it's all painted the internal face is seamless and isn't technically stick-on, the outside face is stick-on, however, but still looks very neat compared to some I've seen. It ain't really pretending to be something it isn't but the real truth is most people don't even notice that a building has double glazing or not.











Fun fact, did you know a 24mm triple glazed unit actually has a worse U-Value than a 24mm double glazed unit? I didn't.


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## G S Haydon (8 Jul 2020)

Agree on tripple glazing, if you want an improvement you need to use a good size unit of 36mm or more.

Linseed oil is great on Accoya and dries fast, very durable too. It does not dry well on some hardwoods. Factory finishing with spray coatings is the best route but not applicable to most hobbyists.

Doug fir is a disaster, I've seen it fail very quickly. Sapele is a nightmare for moisture movement. We are based in the South West so see more issues with that kind of thing.

The timbers I would look at would be Accoya, Red Grandis and Idigbo. I wish European Redwood were better, there's just so much sap wood and defect in it that unless you spend lots of time with preservatives and making it good it's not worth the time.


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