Sash window - a bit lost

[rs6mra]

Hi,

It was a case of wet rot hardener, fill, sand and paint. Then I realized it was worse than I thought.
I am currently preparing the timber for the sill but the bottom ends of the casements need replacing and I have never done this before. I thought of cutting the decayed stuff off at 45 degrees but it seems to be too much - Any guidance would be most welcome

SWMBO (sometimes) comes along and suggests replacing the entire window with a UPVC sash with one of those that can be opened inwards to clean them. I said NO WAY.
However, I'm now considering a timber-framed one but may consider UPVC because it's on the stairs, on the third floor and I hardly ever see it.
Any suggestions

 

[rs6mra]

Photos

 

[Jacob]

I gave up attempting major repairs on sashes early on - loads of work and not very good outcome.
Instead I'd take them out completely and repair/rebuild on the bench, which tended to be no cheaper than doing a complete replica, copying every detail exactly.
They come out and go back in easily - just a wedge or two at each corner. I'd always reuse the glass if it was original.

 

[Adam W.]

I spent a summer working on some of the earliest sash windows from 1720. I could take most of the window apart without having to remove the whole thing from the wall and just insert the bits for security at the end of every day.

I stripped the paint off with a heat gun before taking it apart, otherwise the parting strip would split in two if I didn't.

 

[Just4Fun]

I'd always reuse the glass if it was original.

How do you get the glass out without breaking it? I have some windows I want to work on and that is the bit I am unsure of.

 

[rs6mra]

The window frame thankfully is in tact but the beading between the two sash windows needs repairing but I can’t work or how it’s attached.

 

[JobandKnock]

Parting beads (I think that is what you are referring to) are set in full length grooves and are normally held in with just a few small nails or pins to hold them in place, although zi have seen bridged repairs using screws quite a few times. They do tend to get painted-in, so often you'll need to scrape the accumulated paint off before starting, then pry them out with a couple of chisels. This can split them, however replacements for standard sizes can be had from firms like Reddiseals or Mighton if you don't have a good local timber yard who carry them in stock. Or if you are of Jacob's persuasion, you can always make your own

 

[Adam W.]

That's right parting bead/ strip thingy.

I made my own if they split, but I'd rather re-use the original on such an important historic window. I re-used all the nails and glazing sprigs too and had a friendly glazier who saved me all the old crown glass from any windows he replaced in Bristol.

Lovely chap who could cut glass like he was cutting silk. It was an amazing learning experience watching him work.

 

[Ollie78]

I have written a few comprehensive replies to how to repair sashes properly before, on here somewhere with a bit of searching.

In essence cut the outer cheek and pulley lining out above the rot, cut the new cill to fit along with new pulley lining and cheek. It should then twist into position, bed it on mastic and epoxy it all in.

If you are worried about being able to maintain or clean them use a removable system like mighton cord clamps and a removable bead system (see reddiseals).
At this point you should add draught seals as well.

It's easier than it looks.

For getting original glass out infra red is very good for this, it softens the putty from the back. Or you can use steam or just carefully chisel it out.


Ollie

 

[Jacob]

That's right parting bead/ strip thingy.

I made my own if they split, but I'd rather re-use the original on such an important historic window. I re-used all the nails and glazing sprigs too and had a friendly glazier who saved me all the old crown glass from any windows he replaced in Bristol.

Lovely chap who could cut glass like he was cutting silk. It was an amazing learning experience watching him work.

Glazing sprigs means later addition. You don't find them in original windows, basically because they are not necessary - fresh putty will hold small panes long enough for the putty to go off. Sprigs (and nails in parting slips etc) also become the cause of later breakdown as rust gets to them, putty cracks around them, or pressure on the window starts a break at the sprig.
Need them in big paned windows however, but only temporarily as the putty goes off, then pull out the sprigs and make good.
Say no to sprigs!
Parting slips need to be just a press fit with no fixings of any sort (except the paint), as they need to be removable for servicing purposes.

 

[Adam W.]

I have written a few comprehensive replies to how to repair sashes properly before, on here somewhere with a bit of searching.

In essence cut the outer cheek and pulley lining out above the rot, cut the new cill to fit along with new pulley lining and cheek. It should then twist into position, bed it on mastic and epoxy it all in.

If you are worried about being able to maintain or clean them use a removable system like mighton cord clamps and a removable bead system (see reddiseals).
At this point you should add draught seals as well.

It's easier than it looks.

For getting original glass out infra red is very good for this, it softens the putty from the back. Or you can use steam or just carefully chisel it out.


Ollie

One of the most common causes of decay in timber windows is the use of epoxy, silicone and mastic.

Historically, the components were a dry fit with a few nails for fixing using timber with a zero sapwood content, bedded on lime mortar and finished with proper painting. High quality early vertical hung sash windows had an oak sill

 

[Adam W.]

Glazing sprigs means later addition. You don't find them in original windows, basically because they are not necessary - fresh putty will hold small panes long enough for the putty to go off. Sprigs (and nails in parting slips etc) also become the cause of later breakdown as rust gets to them, putty cracks around them, or pressure on the window starts a break at the sprig.
Need them in big paned windows however, but only temporarily as the putty goes off, then pull out the sprigs and make good.
Say no to sprigs!
Parting slips need to be just a press fit with no fixings of any sort (except the paint), as they need to be removable for servicing purposes.

These were wrought iron sprigs and were dated along with the nails to 1720 by one of the worlds leading experts in historic nails, Dr. Chris How. All the nails were original along with most of the glass.

 

[Jacob]

Getting glass out usually means one or the other: breaking the glass to save the frames, or cutting the frames and pulling them away from the glass (quite easy).
If you want to save both then there are infra red devices but I've never used one. Obvious really - if the glass AND the frame are in good nick then they don't need separating.

 

[Jacob]

One of the most common causes of decay in timber windows is the use of epoxy, silicone and mastic.

Historically, the components were a dry fit with a few nails for fixing using timber with a zero sapwood content, bedded on lime mortar and finished with proper painting. High quality early vertical hung sash windows had an oak sill

Some had oak, many didn't. Oak doesn't hold paint as well as redwood. I've taken windows out where the oak cill has rotted beyond repair but the redwood pulley stiles were still in perfect condition.
The thing about variations and departures from tradition is that it takes 50 years at least to know whether or not they are going to last!- so looking at what has failed is extremely valuable.
Took me some time to discover that modern paints are the kiss of death, and a further 10 years to discover linseed oil paints are possibly the answer. It accounts for the longevity of some old windows I've dealt with which were almost paint free but still serviceable, having lost the paint, compared to others where the modern paint is till bright and shiny but the wood behind is waterlogged and rotted.
Another detail is that in old joinery nothing out of sight is painted, not even with primer. I guess this allows the wood to breathe - gets wet and gets dry again, and of course its a waste of paint and if you paint before fixing it will hold up the job as you wait for it to dry.

 

[NickM]

Lovely chap who could cut glass like he was cutting silk. It was an amazing learning experience watching him work.

Different context, but my Dad used to have a few hundred feet of wooden glass houses in Guernsey (originally they were built for grapes, and then moved into tomatoes and, finally, cut flowers). He frequently had broken panes and was telling me last week that the repairers would hold a large pane of glass in one hand and use the glass cutter in the other and trim the pains whilst sitting 20 feet up in the air on the greenhouse. I find it hard enough cutting glass when it's lying flat on my bench!

This has also just reminded me that my Grandpa and a friend once rode a bicycle along the ridge of a greenhouse when they were kids. That could have ended badly...

 

[Jacob]

These were wrought iron sprigs and were dated along with the nails to 1720 by one of the worlds leading experts in historic nails, Dr. Chris How. All the nails were original along with most of the glass.

I've never found (old) sprigs in old windows - oldest being from about 1790. Chris How's sprigs might have been an anomaly. Why would anybody use sprigs except temporarily, as otherwise they have no function and can be a cause of subsequent failure? * Not only that but commonly glazing rebates are down to 5mm - not enough to cover the sprig.
PS * failure being the putty cracking around the sprig, or even worse a tight fitting sprig spalling or starting a crack in the glass

 

[Jacob]

Glass cutting is an odd one. I've got at two similar diamond cutters but only one of them works and it's the cheaper one. If you only had the other you'd assume glass cutting is difficult!
Key is very clean glass, good cutter and one confident movement. A few taps and presses first may help it on its way rather than just going for it. Just a bit of pressure and you can sometimes see the crack shooting along the cut line. Glazing pliers help. Old glass cuts easily unless it's very varied in thickness.

 

[johnnyb]

I'm not commenting on how to repair as Jacobs yer man there.
but the masonry underneath seems to have no forward angle to shed the water. this may have allowed water to sit beneath the window. the devil's always in the detail!

 

[Jacob]

I.......
but the masonry underneath seems to have no forward angle to shed the water. this may have allowed water to sit beneath the window. the devil's always in the detail!

Absolutely. They need a good fall or failing that some carefully fitted lead flashing.

 

[Adam W.]

I've never found (old) sprigs in old windows - oldest being from about 1790. Chris How's sprigs might have been an anomaly. Why would anybody use sprigs except temporarily, as otherwise they have no function and can be a cause of subsequent failure? * Not only that but commonly glazing rebates are down to 5mm - not enough to cover the sprig.
PS * failure being the putty cracking around the sprig, or even worse a tight fitting sprig spalling or starting a crack in the glass

They were my sprigs and he stole them from me...I kept one though and it's in my marking gauge it's tiny and under 1mm thick. If they were later they would have been made from slit stock and not bar.

I collected a large number of nails for his thesis and he had me dragging a magnet on a rope around the reclamation yards of Somerset during my spare time.

The oak sills were original too and the earliest windows had boxwood pulleys with rectangular lead weights. Lovely windows. There was also a fixed window with broad glass in it, didn't dare touch it though.