Replacing Glazing in Wooden Frames

[DIYWell]

I'm planning to replace the glazing in a window. It's currently single glazed and I want to replace it with a double glazed unit since there's sufficient depth. Internally the glazing is kept in place with a quadrant bead.

Wood to wood dimensions are 1980x610 but I need to order slightly smaller to allow for expansion and fitting, but how much smaller?

The last time I fitted glass was single glazing and linseed putty. I presume glazing technology has moved on so any guidance of how to fit would be welcome.

 

[Doggit]

This is a bit non standard, so using linseed putty may not work properly, but allow 5mm all round the glass for expansion, set it in place with some packing pieces to get the right position, but not to make it too tight, tap some panel pins in to keep it in place, and the seal it in place with linseed oil, or uses some small quadrant, and take the panel pins out as you go, but run a bead of sealant between the glass and the beading to keep out the water.

 

[DIYWell]

Sorry, should have said the original glass was fitted from the inside against the lip and quadrant on the inside.

When the house was built, this would have been an external window, but now it's internal since a porch was built, so I've no worries about rain.

 

[DIYWell]

... run a bead of sealant between the glass and the beading to keep out the water.

What sort of sealant? Surely not a silicon one?

 

[Doggit]

Then there won't be an issue, will there.

 

[Burnerman]

I've used a high modulus silicone on all of my units, and had no problems in 30 years. Definitely use some sort of sealant though as the pane could rattle otherwise. Wickes do a putty in a tube if that's what you want to use.
John

 

[crank39]

Linseed putty is an absolute no no when it comes to double glazed units and it's been known to be for at least 20 years, the linseed oil attacks the seal and the units will fail within a year or so, sometimes sooner, use a silicone suitable for glazing

 

[Burnerman]

Are you considering a double glazed unit for sound or warmth, as its inside?
I used those square rubber pads that come with the units to space the unit up from the bottom of the frame, and finish off with glazing silicone.
John

 

[crank39]

Are you considering a double glazed unit for sound or warmth, as its inside?
I used those square rubber pads that come with the units to space the unit up from the bottom of the frame, and finish off with glazing silicone.
John

Another no no John, both bottom edges need to be be supported equally as when it warms up in summer and the holtmelt/polysulphide seal softens one pane may slide or sink relative to the other one and again break the seal, if youve got away with it so far i would imagine the transport pads have compressed so much near on straight away that both panes are sitting hard on the timber, but then you have the drainage issue associated with DGUs in timber frames but that's for another thread lol!

 

[Burnerman]

Wow I live and learn and really appreciate your comments
I made my own window frames from sapele, and sat each glazing unit unit on four of those pads. The thickness of the unit was enough to be supported by the pads - presumably the units are thicker now?
Anyway - not knowing what I was really doing, some of the units were puttied in, others had glazing beads with brass sprigs and clear glazing silicone. I had no idea (and still don't) the requirements for drainage. The timber finish is dark Sadolin, and regularly reapplied.
Only three units have failed to date and surprisingly these weren't the biggest ones so I guess lady luck was on my side!
As the OP's unit is internal do you think he'll get away with it?
Thanks, crank.
John

 

[crank39]

Internal or external you'd still have to stop water penetration past the putty/gasket or silicone. What I'd do if you really must fit DGUs in timber frames is bed them on clear silicone, ensure about 5mm gap under the dgu, you do not want water touching the dgu at all, any prolonged exposure will fail the unit, it can be as quick as 3 months up to a year but they will fail.

Pvc windows are ideal to drain water away as the sections are hollow so you can direct water away from the unit very efficiently, with timber you have to start notching out slots under the bead to let water escape or drill diagonally down from the glazing packer area outwards eventually exiting just below the bead, some stuff the hole with a bit of fibreglass insulation, allows water to escape but stops bugs getting in, like I say incorporating some sort of drainage in timber can be tricky, it can be done but is rare to find

 

[Notch7]

I'm planning to replace the glazing in a window. It's currently single glazed and I want to replace it with a double glazed unit since there's sufficient depth. Internally the glazing is kept in place with a quadrant bead.

Wood to wood dimensions are 1980x610 but I need to order slightly smaller to allow for expansion and fitting, but how much smaller?

The last time I fitted glass was single glazing and linseed putty. I presume glazing technology has moved on so any guidance of how to fit would be welcome.

Sorry, should have said the original glass was fitted from the inside against the lip and quadrant on the inside.

When the house was built, this would have been an external window, but now it's internal since a porch was built, so I've no worries about rain.

Your situation is a bit unusual as you have no rain penetration issues. You havent said if the porch is fully enclosed or not.

Im guessing the porch is unheated so you want to fit double glazing for warmth.

Unit size:
Normally a double glazed unit would have a 4mm-5mm air gap around it, In which case the unit would height and width less say 8mm.

I would suggest a spec of soft coat low e with warm edge spacer. It needs to be toughened glass if below 800mm or next to a door.

However bear in mind the spacer in a double glazed unit is usually 12mm, so if your existing rebate is small, which it probably is, then the new unit once fitted will have visible spacer showing around the edge.

If necessary make the unit a bit tighter on the width, say 3mm each side. But its best keep a 5mm gap at the bottom, so there is a bit of an air gap to help with condensation.

I would put 5mm packefs on the bottom to keep that space. If you dont use proper glazing shims make sure your improvised shim supports both panes of glass.

I would simply use neutral cure silicone, a thin bead around before the glazing beads go on. Do not fill up the gap, the unit needs that air gap

https://www.screwfix.com/p/no-nonsense-builders-silicone-clear-310ml/83710