Advice on repair of sliding sash windows

[Bristol_Rob]

Luckily that is of no concern because we have an expert overseeing the project, He one of the UK’s most experienced Chartered Building Surveyors in the area of historic and Listed Buildings, he is Chair of the RICS Building Conservation Steering Group and he teaches building surveying, architectural history, building pathology and building conservation to undergraduate and postgraduates.

Interesting, who is your expert?

 

[Ollie78]

I have repaired many hundreds of sliding sashes and used repair care (overpriced) and the timbabuild stuff which used to be a ventrolla exclusive product years ago.
Each one is different, some need to be removed and if the building is being fully replastered or something then this is a good way to go, however often its not worth the colateral damage especially if there is shutters and stuff.
Also the conservation requirements vary enormously per job, once I found myself cutting in partial sections of oak glazing bars as invisibly as possible to an old window, it took several days and I could have made a virtually identical new pair of sashes in the time but that was the brief so thats what I did.

Many conservation people have little idea how stuff is actually constructed and need to be talked through the process, some are great and know what is involved, these ones normally just let you get on with it.

Cutting out and replacing cill section in situ is pretty easy once you have done a few, I would say allow half a day.
I normally cut out the pully lining to above the pocket (this way you get a nice new pocket too) then cut out the outer cheek to above where the rot is. Inner cheek is often fine but don`t forget to cut the pins. Cut the cill in the middle and lift it up from there in two bits, clean it all up. Make replacement bits and re-assemble using timbabuild erc 10. Sand and paint.

Use more timber and less resin, use it only as a glue/filler if possible.
Incidentally replacing both sashes, the cill and half the lining is still a repair, replacing the sashes is almost always a better job if they will let you do it, you don`t need to scrape and paint them etc..


Ollie

 

[RobinBHM]

I have repaired many hundreds of sliding sashes and used repair care (overpriced) and the timbabuild stuff which used to be a ventrolla exclusive product years ago.
Each one is different, some need to be removed and if the building is being fully replastered or something then this is a good way to go, however often its not worth the colateral damage especially if there is shutters and stuff.
Also the conservation requirements vary enormously per job, once I found myself cutting in partial sections of oak glazing bars as invisibly as possible to an old window, it took several days and I could have made a virtually identical new pair of sashes in the time but that was the brief so thats what I did.

Many conservation people have little idea how stuff is actually constructed and need to be talked through the process, some are great and know what is involved, these ones normally just let you get on with it.

Cutting out and replacing cill section in situ is pretty easy once you have done a few, I would say allow half a day.
I normally cut out the pully lining to above the pocket (this way you get a nice new pocket too) then cut out the outer cheek to above where the rot is. Inner cheek is often fine but don`t forget to cut the pins. Cut the cill in the middle and lift it up from there in two bits, clean it all up. Make replacement bits and re-assemble using timbabuild erc 10. Sand and paint.

Use more timber and less resin, use it only as a glue/filler if possible.
Incidentally replacing both sashes, the cill and half the lining is still a repair, replacing the sashes is almost always a better job if they will let you do it, you don`t need to scrape and paint them etc..


Ollie

Many thanks for the advice.

This is ongoing so I will post some images over the weekend.

 

[Windows]

How did this project go? I think I missed the images.

 

[johnnyb]

I'd like to see some pics if you have time.

 

[RogerS]

Don't bother taking them out, as you can take them apart from both sides whilst in situ easily enough.

Taking them out and re-fitting is a complete waste of time.

Plus you waste more time 'making good' of all the plasterwork.

 

[Jacob]

Plus you waste more time 'making good' of all the plasterwork.

With a good plasterer can be a lot easier than "making good" the woodwork in situ rather than on the bench.
I was always into taking them out and doing them in the workshop. Better job and cheaper too.
Beyond a certain point things often need total restoration rather than repair.

 

[johnnyb]

I would always try and sell the proper repair. I can't stand seeing repairs I've done deteriorate in under 5 years. I just think " should have done it properly" that's best for everyone usually. splicing is a bodge usually especially with sash repairs.

 

[johnnyb]

you often find very badly rotted windows have a fitting issue ie water runs under them. maybe the stone cill has weathered wrong or a fault line.

 

[Adam W.]

.

 

[Clarke]

My box frame repairs are very similar to @Ollie78.

I take out the pulley stile, cutting at the point just above the bottom of the meeting rail of the top sash which hides the join permanently. I always make the new pockets bigger as I’m usually replacing for longer weights which won’t fit through the original pockets.

Then take out the cill. It’s easier now the pulley stile is gone since that is rebated into the cill. The more rotten, the easier it is to remove.
Tip when cutting through the cill. Take off internal mouldings first or use a multi tool to separate if leaving in place and before you finish the cut, crowbar up the cill slightly and you won’t run the saw over the concrete cill.

Take measurements of the distance between inner and outer faces and the distance between pulley stiles (both measurements at the top of the frame) and compare to the bottom. Any discrepancy can be a problem if draught-proofing. The top of the frame usually remains more stable and is a more accurate indication of original dimensions.

Cut new cill.
- Two rebates to hold the pulley stiles. Distance between rebates to match the measurement taken from the top of the frame. This keeps everything square (or straight at least) Drill 3-4mm holes right through the bottom of the rebates to help drain future ingress of water.
- extend the cill section min. 1 3/4” past the pulley stile, cutting a ‘tenon’ on the ends of the cill with the width matching the distance measured earlier (between outer/inner face at the top). The thickness of the inner lining dictates the distance the tenon is offset so that the cill sits flush with the inside of the frame. Some cill designs extend out past the outer lining but in all cases they are flush on the inside.

Now sort the weights out whilst you have good access (pulley stile is cut away).

Assuming rot in the outer lining, cut it away but always at least 6” below the cut you made in the pulley stile. This staggers the repairs and is much stronger. The cut needs to be angled downward regardless of whether straight scarf or step-joint.
Obviously, replacing the whole length is preferable but not practical in most instances.

Before making any cuts in the inner lining (and as long as your happy with its position) use it as a reference to locate the new pulley stile, which you cut earlier with the relevant tongues on each side, parting groove etc

Sometimes the cill can be slid in from the front, other times it needs to be placed from above before the new pulley stiles go in.

Move the cill side-to-side until the pulley stiles are square with rest of frame. Pin the inner lining to the pulley stile to hold everything in place. Don’t tap pins home if replacing inner lining.

Replace outer lining. Blah blah.

Now change inner lining as appropriate. Blah blah.

Now take everything out, sand everything, prime the bits that need priming, realise you just took out all your references, realise it doesn’t matter cos you’ve done this a thousand times before and you made quick and experienced notes and pencil marks on the masonry, frame, phone and photos, knife marks in places where pencil marks would get sanded off and/or primed over, made mental notes where you thought that cos you’ve done this a thousand times before that you don’t need written references, then forget, then remember as it’s going back together just in the nick of time.

I could drag this post out to ten thousand words just on this one type of repair and that actually, this represents a fraction of potential scenarios, window designs, location in the wall, potential problems and a million other things to look out for. I also realise that it’s incredibly difficult to know what I’m talking about unless ‘you know’.

Welcome to the world of sash window repair.

Oh and one more thing. Dryseal for the splice joints. Glue will never do. I don’t care how good you think your splices are.

Oh yeah, pack the cill up on slate and make sure the pulley stile and outer/inner linings are cut shy of the stone cill. This means you need to make the replacement cill slightly thinner or simply use it as a good excuse to trim the sashes which means you need to take out the sashes and errrr……’it’s just a window right?’ ‘Why does it take so long?’ ‘Can’t you just?…..’. No. No I can’t. Or rather, I won’t. I don’t want to. I do it properly or nuffink.

Yeah.

 

[Jacob]

My box frame repairs are very similar to @Ollie78.

I take out the pulley stile, cutting at the point just above the bottom of the meeting rail of the top sash which hides the join permanently. I always make the new pockets bigger as I’m usually replacing for longer weights which won’t fit through the original pockets.

Then take out the cill. It’s easier now the pulley stile is gone since that is rebated into the cill. The more rotten, the easier it is to remove.
Tip when cutting through the cill. Take off internal mouldings first or use a multi tool to separate if leaving in place and before you finish the cut, crowbar up the cill slightly and you won’t run the saw over the concrete cill.

Take measurements of the distance between inner and outer faces and the distance between pulley stiles (both measurements at the top of the frame) and compare to the bottom. Any discrepancy can be a problem if draught-proofing. The top of the frame usually remains more stable and is a more accurate indication of original dimensions.

Cut new cill.
- Two rebates to hold the pulley stiles. Distance between rebates to match the measurement taken from the top of the frame. This keeps everything square (or straight at least) Drill 3-4mm holes right through the bottom of the rebates to help drain future ingress of water.
- extend the cill section min. 1 3/4” past the pulley stile, cutting a ‘tenon’ on the ends of the cill with the width matching the distance measured earlier (between outer/inner face at the top). The thickness of the inner lining dictates the distance the tenon is offset so that the cill sits flush with the inside of the frame. Some cill designs extend out past the outer lining but in all cases they are flush on the inside.

Now sort the weights out whilst you have good access (pulley stile is cut away).

Assuming rot in the outer lining, cut it away but always at least 6” below the cut you made in the pulley stile. This staggers the repairs and is much stronger. The cut needs to be angled downward regardless of whether straight scarf or step-joint.
Obviously, replacing the whole length is preferable but not practical in most instances.

Before making any cuts in the inner lining (and as long as your happy with its position) use it as a reference to locate the new pulley stile, which you cut earlier with the relevant tongues on each side, parting groove etc

Sometimes the cill can be slid in from the front, other times it needs to be placed from above before the new pulley stiles go in.

Move the cill side-to-side until the pulley stiles are square with rest of frame. Pin the inner lining to the pulley stile to hold everything in place. Don’t tap pins home if replacing inner lining.

Replace outer lining. Blah blah.

Now change inner lining as appropriate. Blah blah.

Now take everything out, sand everything, prime the bits that need priming, realise you just took out all your references, realise it doesn’t matter cos you’ve done this a thousand times before and you made quick and experienced notes and pencil marks on the masonry, frame, phone and photos, knife marks in places where pencil marks would get sanded off and/or primed over, made mental notes where you thought that cos you’ve done this a thousand times before that you don’t need written references, then forget, then remember as it’s going back together just in the nick of time.

I could drag this post out to ten thousand words just on this one type of repair and that actually, this represents a fraction of potential scenarios, window designs, location in the wall, potential problems and a million other things to look out for. I also realise that it’s incredibly difficult to know what I’m talking about unless ‘you know’.

Welcome to the world of sash window repair.

Oh and one more thing. Dryseal for the splice joints. Glue will never do. I don’t care how good you think your splices are.

Oh yeah, pack the cill up on slate and make sure the pulley stile and outer/inner linings are cut shy of the stone cill. This means you need to make the replacement cill slightly thinner or simply use it as a good excuse to trim the sashes which means you need to take out the sashes and errrr……’it’s just a window right?’ ‘Why does it take so long?’ ‘Can’t you just?…..’. No. No I can’t. Or rather, I won’t. I don’t want to. I do it properly or nuffink.

Yeah.

Strewth!
Beyond normal servicing and adjusting, I gave up repair in situ after the first few goes as usually much easier to remove the whole thing and do it in the workshop.
Usually cheaper to just copy and make a new one but sometimes a restoration/rebuild called for.
Usually very easy to remove, very easy to refit.

 

[Clarke]

Strewth!
Beyond normal servicing and adjusting, I gave up repair in situ after the first few goes as usually much easier to remove the whole thing and do it in the workshop.
Usually cheaper to just copy and make a new one but sometimes a restoration/rebuild called for.
Usually very easy to remove, very easy to refit.

Most of the sashes I work on are covered in panelling, mouldings, folding shutters etc.
Easier to repair on the bench but you add a fair few days of making good so, at least for me, it’s not economical.