Making Box Sashes, wood choice etc

[deema]

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.

 

[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.

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

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?

 

[Flat Pat]

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?

 

[Trevanion]

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.

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.

 

[LBCarpentry]

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!

 

[Flat Pat]

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

 

[thomashenry]

What reason would there be for NOT using linseed paint?

 

[Trevanion]

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:

 

[thomashenry]

It really doesn't take THAT long.

 

[thomashenry]

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.

 

[Flat Pat]

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.

 

[RogerS]

....
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 !

 

[RogerS]

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.

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.

 

[Trevanion]

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.

 

[G S Haydon]

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.