Making Box Sashes, wood choice etc

[Flat Pat]

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?

 

[Trevanion]

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.

 

[Flat Pat]

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:

 

[Flat Pat]

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?

 

[Trevanion]

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.

 

[Flat Pat]

OK, sounds like Accoya is the way to go.

 

[Doug71]

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.

 

[Flat Pat]

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.

 

[Artiglio]

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.

 

[Flat Pat]

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.

 

[Flat Pat]

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

 

[thetyreman]

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.

 

[Doug71]

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.

 

[Flat Pat]

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.

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

 

[LBCarpentry]

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.

 

[Trevanion]

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.

 

[Flat Pat]

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.

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.

 

[deema]

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

 

[AndyT]

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.

 

[LBCarpentry]

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.