How do I install a sash window?

[dpmstevens]

Hello. I'm about to make a new sash window frame to replace the piece of junk UPVC thing we've been suffering with since we bought the house. I've got an original frame from the neighbour's house to copy, so it will be an exact replica.

Not sure how to fit it though. I'm guessing the traditional folding wedges, but the problem is, there's no way to get them between the top of the box and the underside of the timber lintel. I'd have to remove the plaster to do so, which I'd rather not. I can get them between the sill and the stone below, but I imagine it's going to need more than that to hold it in.

In the close up picture of one of the other window reveals, you can see a piece of timber which has been nailed to the upper noggin, and there's a corresponding piece on the noggin below. I think this is part of the back of the box, so perhaps it was nailed through as well?

Am I missing something here? (And no, it's not expanding foam as I'm not using it in this house.) Or is there another way that doesn't involve damaging the plaster?

Cheers
Dan

 

[Jacob]

......

Am I missing something here? (And no, it's not expanding foam as I'm not using it in this house.) Or is there another way that doesn't involve damaging the plaster?

Cheers
Dan

If there were sashes originally (looks like there was) you've just got to reverse engineer until you can fit the new one and then make good afterwards. Probably impossible to do without damaging the plaster and a few other things too. Your plaster looks damaged already!
To fit leave off the inside linings, fit the rest first with folding wedges, linings last - scribed to fit the masonry if necessary. Then window board, then plaster.

 

[Doug71]

Is the window going in from the inside or the outside?

 

[rogxwhit]

Don't fully understand your context. There are 2 basic scenarios - window installed from inside, or from outside. What's this one?

Wedges in my experience are used laterally at head and sill. The block above the head seems weird but I can't see how it relates to the outside. Is it a plastic window bodge? I wouldn't wedge under a sill, ever.

Obviously you can't wedge the unsupported backs, except where the head and sill reinforce them.

 

[Jacob]

Is the window going in from the inside or the outside?

Sash windows nearly always go in from the inside.

 

[rogxwhit]

No, Jacob, sorry. Your experience has missed a trick. In some areas and wall constructions at least, installation from outside is the more prevalent. the sashes will, admittedly ...

 

[Jacob]

No, Jacob, sorry. Your experience has missed a trick. In some areas and wall constructions at least, installation from outside is the more prevalent.

I know earlier types can be done but its still easier from the inside, not least because half of them are likely to be on the upper floor. And there's far more of the later type which fit neatly into a masonry rebate from the inside - impossible from outside.
Even if you can do them from the outside you're going to have to get in there to hang the sashes themselves and make good all round.

 

[Housey210]

Box sashes put in at build. The great fire of london caused a major rethink so hence the box is behind outer wall with little wood showing. The inner brick leaf may hold the box in place but usually the lining tongued into box and fixed to propellor wedges driven into inner leaf joints. Spiral spring balances save on making a box and the overal size.

 

[rogxwhit]

There's a technique that may be 'rustic' but involves positioning wedges, without any masonry stop in or out - and the sash box is then plastered up to inside and the outer mortared up to (overlapping slightly) outside. In which case the easiest replacement tends to be from outside, butting up to the existing window board and plaster.

 

[niall Y]

Not sure I get the complete gist of what you are saying, but windows are normally screwed in position. either directly through the frame, or with galvanized straps to the sides, they are then fixed to the brickwork and plastered over. There is no picture of the outside so I'm assuming you can fit them from the outside i.e. they are not set behind a rebate formed by the outer skin of brickwork

If we are talking about a box-sash, then in most buildings in metropolitan areas, these are installed from the inside and are flush with internal wall, and fit inside a rebate formed by the outside brickwork. These can be secured with wedges, but straps would also be advisable.

If it is a box-sash, and fitted flush with the outside, then you will have to fasten it with straps, and chisel out slots in the plaster to accommodate them

In the past window frames ( and it looks like this is an old property) were set into the brickwork using their horns ( small extensions to the top of the frame and sill)
Its a lot easier not to bother with these for replacement work

 

[Jacob]

Box sashes put in at build.

Not very likely. Too fragile too vulnerable to weather and always an easy fit in a finished opening

The great fire of london caused a major rethink so hence the box is behind outer wall with little wood showing.

It's also a much easier fit, more weathproof and architecturally neater with just an inch or so of outside lining showing

The inner brick leaf may hold the box in place but usually the lining tongued into box

Usually wedged at each end of top rail and bottom cill

and fixed to propellor wedges driven into inner leaf joints.

Not necessary. Nearly always just wedged and then held by plaster. Also makes them very easy to remove and renovate on the bench instead of in situ.

Spiral spring balances save on making a box and the overall size.

No point in a renovated/replaced sash but may have their uses in new work. I've never used them myself

 

[Jacob]

There's a technique that may be 'rustic' but involves positioning wedges, without any masonry stop in or out - and the sash box is then plastered up to inside and the outer mortared up to (overlapping slightly) outside. In which case the easiest replacement tends to be from outside, butting up to the existing window board and plaster.

Except you still have to go inside to hang the sashes themselves and make good around. Even more PITA if on a higher floor.
I turned down several biggish jobs where they wanted them done from outside - have to increase the estimate by 50% or more for the scaffolding and the sheer difficulty.

 

[Jacob]

.....

In the past window frames ( and it looks like this is an old property) were set into the brickwork using their horns .....

Not sashes - always wedged.

 

[Ollie78]

Wedged as most are saying.
Make proper pairs of wedges long enough to contact outer and inner cheek. You should be putting a back on the box as well.
Foam around for airtightness then sort out the reveals.

Spiral balances are one of the worst things ever invented, so avoid them at all costs.

Ollie

 

[dpmstevens]

The window is going in from the inside.

The plaster is a little damaged where the old sash was removed 20 years ago. I'd rather not have to cut back the lath and the stud and remove the beading. I wonder about using wedges on the sill, then using screws to fix the header to the lintel. I could add a back to the header U section to make a box. Two small pockets cut into the underside of the header box would give access to the back so I could fit two screws into the lintel, then replace the pockets as per the weight pockets.

The block above the frame is a plastic window bodge. Disregard anything you see in the pictures that isn't made of wood, as the UPVC fitment is a mess.

 

[dpmstevens]

Wedged as most are saying.
Make proper pairs of wedges long enough to contact outer and inner cheek. You should be putting a back on the box as well.
Foam around for airtightness then sort out the reveals.

Spiral balances are one of the worst things ever invented, so avoid them at all costs.

Ollie

Boxes will have backs as per the original. Definitely no spiral balances. Some of the windows in the downstairs extensions have them. They're rubbish.

 

[Housey210]

Not very likely. Too fragile too vulnerable to weather and always an easy fit in a finished opening

It's also a much easier fit, more weathproof and architecturally neater with just an inch or so of outside lining showing

Usually wedged at each end of top rail and bottom cill


Not necessary. Nearly always just wedged and then held by plaster. Also makes them very easy to remove and renovate on the bench instead of in situ.

No point in a renovated/replaced sash but may have their uses in new work. I've never used them myself

"As a precautionary measure against the spread of fire, the 1709 Building Act stipulated that the corners of a Box sash frame must be hidden behind the face of the brick or stone and that "no door or window frame of wood shall be set nearer to the outside face of the wall than four inches". In 1774 this distance was increased to nine inches, and nearly the entire frame had to be hidden behind the face of the wall. While this legislation was only applicable to the cities of London and Westminster, the styles they produced became fashionable and sliding sash window installations spread throughout England within about twenty years."

The sash box in the day is NO different to window profiles being put in at build stage today, replaced by plastic when roofed in. The sashes are seperate and as dg units in plastic today easily retro fitted. FRAGILE! A box, behave.

 

[Jacob]

"As a precautionary measure against the spread of fire, the 1709 Building Act stipulated that the corners of a Box sash frame must be hidden behind the face of the brick or stone and that "no door or window frame of wood shall be set nearer to the outside face of the wall than four inches". In 1774 this distance was increased to nine inches, and nearly the entire frame had to be hidden behind the face of the wall. While this legislation was only applicable to the cities of London and Westminster, the styles they produced became fashionable and sliding sash window installations spread throughout England within about twenty years."

The sash box in the day is NO different to window profiles being put in at build stage today, replaced by plastic when roofed in. The sashes are seperate and as dg units in plastic today easily retro fitted. FRAGILE! A box, behave.

I've taken out 100s of old sashes and non of them looked like they'd been built in. Too fragile - they are a bit bendy and could easily be put out of square.

 

[rogxwhit]

Foam around for airtightness then sort out the reveals.

Whoa! Foam can pressure & distort the often thin backs, even to the point of trapping the weights. Be cautious.

 

[rogxwhit]

Not for the present circumstance, just for interest, Jacob in particular, but when the reveal has no returns (stops), at first build the box can be installed from in or out. I doubt that replacement was considered at that stage, but when the time came 100+y later it was less disruptive to plaster & decor to install the replacement from o/s. I've done many off a ladder at ground & first floor. It's only the box you have to shoulder up. That's windows of modest domestic scale.