Sash windows build advice on compliance..

[JC800]

Hi all,

I want to build my own sash windows for an Edwardian semi and not quite sure what the requirements for compliance are given my circumstances. When I bought the house upvc double glazed windows were and still are in place. I’ve salvaged a set of original sash windows from a neighbouring property which require some repairs so first question is can I get away with installing these with the necessary repairs made? If so I’d be wanting to upgrade the glass to double glazing so my second question is what would be the maximum thickness I could use given the sashes are 44mm thick?

That would be one set of circumstances, but in the event the rules won’t allow for the above option then it’s on with making my own. I am under the assumption I would not get away with like for like construction methods? So if that is the case then is there any available resource online I can seek guidance from?… I’ve done many a search but only window companies come up. Say if I wanted to use 10mm double glazed units would I need to alter the spec of the sash and casement thickness? Again, does anyone know of any available resource that stipulate the requirements for frame thickness to glazing thickness?

Thanks in advance.

 

[Ollie78]

You should be fine using a slim DGU with 8mm sightline and krypton or xenon ( I forget which is the best now ) use Hodgesons heritage putty for glazing, never use linseed oil on double glazed units, and silicone is a nightmare.
You will need to make new sashes to accommodate the additional glass thickness.
Old ones can be adapted sometimes but by the time you have messed about with them it's quicker and easier to do new ones.

16mm (4/8/4) maybe 18mm ( 4/10/4 )units should go in a 44mm thick sash if you make them right this will allow a 6mm putty line.
Glazing bar thickness is going to have to be the sight line of 8mm twice plus whatever you can get away with 5mm being the minimum I would allow before it gets too skinny
So 16mm plus 5mm is 21mm which is still pretty slim.

You may need custom knives if they are going force you to copy the mouldings of existing ones exactly but often you can just use a small flat ovolo and adjust the rebate to allow the glazing.

You will not be complying with modern part L, you are "restoring and upgrading existing as best you can"
This is "conservation "work not new build so this is the angle you need to use.

Have fun

Ollie

 

[deema]

If it’s not in a conservation area, locally or nationally listed, rip the hell out of it. Modernise it as much as possible. Sod heritage, the lefty idiots on the council can just for the fun of it slap a local listing on your ‘castle’ and then your royally ‘flocked’ at being able to upgrade it to make it habitable for the 21 century. Triple glazed modern units all the way. The less ‘heritage’ there is the less likely you are to get a local order. This is talking from bitter experience.

 

[niall Y]

Pilkington Spacia? ................ but God knows how much it costs!
Ooops... just found out £250 per sq. metre

 

[Ollie78]

If it’s not in a conservation area, locally or nationally listed, rip the hell out of it. Modernise it as much as possible. Sod heritage, the lefty idiots on the council can just for the fun of it slap a local listing on your ‘castle’ and then your royally ‘flocked’ at being able to upgrade it to make it habitable for the 21 century. Triple glazed modern units all the way. The less ‘heritage’ there is the less likely you are to get a local order. This is talking from bitter experience.

I agree in some ways I would love some nice Internorm aluminium and wood composite windows with internal blinds. They are great windows. Then I finally managed to get a price for one (small ish one fixed one opening side) it was nearly 3 grand.. for one !!!

Ollie

 

[Jacob]

If you want replica period sashes then forget double glazing, it's totally incompatible with trad design. Instead look at having internal shutters or secondary glazing, or even just thermal blinds.

 

[Jacob]

If it’s not in a conservation area, locally or nationally listed, rip the hell out of it. Modernise it as much as possible. Sod heritage, the lefty idiots on the council

Nothing lefty about conservation. There's a clue in the name - think "conservative".

 

[deema]

Labour council. Hardly describe them as right wing conservatives? They also slapped a Tree Preservation Order on the entire front garden…….which hasn’t any tress in it. In the village another of their imaginative decisions was to slap a local listing on a house that was in the process of combining a cattle shed into it……the shed had and now has to have an asbestos corrugated roof on it. The house roof is now half modern and half corrugated lung disease: you simply can’t make this stuff up.

 

[JC800]

You should be fine using a slim DGU with 8mm sightline and krypton or xenon ( I forget which is the best now ) use Hodgesons heritage putty for glazing, never use linseed oil on double glazed units, and silicone is a nightmare.
You will need to make new sashes to accommodate the additional glass thickness.
Old ones can be adapted sometimes but by the time you have messed about with them it's quicker and easier to do new ones.

16mm (4/8/4) maybe 18mm ( 4/10/4 )units should go in a 44mm thick sash if you make them right this will allow a 6mm putty line.
Glazing bar thickness is going to have to be the sight line of 8mm twice plus whatever you can get away with 5mm being the minimum I would allow before it gets too skinny
So 16mm plus 5mm is 21mm which is still pretty slim.

You may need custom knives if they are going force you to copy the mouldings of existing ones exactly but often you can just use a small flat ovolo and adjust the rebate to allow the glazing.

You will not be complying with modern part L, you are "restoring and upgrading existing as best you can"
This is "conservation "work not new build so this is the angle you need to use.

Have fun

Ollie

Thanks for this Ollie. Good to know I’m not obliged to go supersized thickness to cater for 10mm dgu’s. I’m planning on boarding the outer walls with the insulated stuff so if I make new sashes I don’t mind going a bit wider, but not so much as to look odd. I’m not in a conservation area… So I’m wondering if becoming Fensa certified myself is the get out clause from having to deal with council inspectors

 

[Jacob]

Labour council. Hardly describe them as right wing conservatives? They also slapped a Tree Preservation Order on the entire front garden…….which hasn’t any tress in it. In the village another of their imaginative decisions was to slap a local listing on a house that was in the process of combining a cattle shed into it……the shed had and now has to have an asbestos corrugated roof on it. The house roof is now half modern and half corrugated lung disease: you simply can’t make this stuff up.

They are only trying to stop the place going to the dogs! Sometimes they get things wrong.

 

[deema]

Just ‘repair’ the windows. I had a really interesting conversation on what is repair and what is replace with a building inspector. In the end, as long as any part of the original exists, or remains from what was there before you started to repair, it’s a repair. So, taking it to an extreme, if you reuse a screw, it’s a repair. I know, madness, but that’s the literal interpretation as I understand it of the rules.

 

[JC800]

If it’s not in a conservation area, locally or nationally listed, rip the hell out of it. Modernise it as much as possible. Sod heritage, the lefty idiots on the council can just for the fun of it slap a local listing on your ‘castle’ and then your royally ‘flocked’ at being able to upgrade it to make it habitable for the 21 century. Triple glazed modern units all the way. The less ‘heritage’ there is the less likely you are to get a local order. This is talking from bitter experience.

It’s not a conservation area, but imo worthy of being conserved. Modding out is the no brainer for all the obvious reasons. I’ve just got the itch to restore, I’m on a 50/50 street ratio of conserved to modified. It’s a nice street in an average area. If most of it was modern I’d stick with my existing set up. Possibly I’m guilty of purist snobbery but I see worth in keeping things original… It’s one of them where charm trumps practicality.. but at least I ain’t a leftie

 

[JC800]

Just ‘repair’ the windows. I had a really interesting conversation on what is repair and what is replace with a building inspector. In the end, as long as any part of the original exists, or remains from what was there before you started to repair, it’s a repair. So, taking it to an extreme, if you reuse a screw, it’s a repair. I know, madness, but that’s the literal interpretation as I understand it of the rules.

If I get an inspector who approves repairs then great. Just concerned as they’re salvaged they won’t qualify as the original, that coupled with no sashes having been in for at least 30 years..

 

[Fitzroy]

I’ve been messing around with the sashes on my place and put a thin 14mm (4-6-4) krypton DGU in one of the sashes. I’m not impressed with the performance. It steams up whilst cooking, whereas the 24mm DGU in the door doesnot.

 

[Bristol_Rob]

never use linseed oil on double glazed units.

What makes you say this?

 

[Seascaper]

Hi all,

I want to build my own sash windows for an Edwardian semi and not quite sure what the requirements for compliance are given my circumstances. When I bought the house upvc double glazed windows were and still are in place. I’ve salvaged a set of original sash windows from a neighbouring property which require some repairs so first question is can I get away with installing these with the necessary repairs made? If so I’d be wanting to upgrade the glass to double glazing so my second question is what would be the maximum thickness I could use given the sashes are 44mm thick?

That would be one set of circumstances, but in the event the rules won’t allow for the above option then it’s on with making my own. I am under the assumption I would not get away with like for like construction methods? So if that is the case then is there any available resource online I can seek guidance from?… I’ve done many a search but only window companies come up. Say if I wanted to use 10mm double glazed units would I need to alter the spec of the sash and casement thickness? Again, does anyone know of any available resource that stipulate the requirements for frame thickness to glazing thickness?

Thanks in advance.

Hello,
I repaired my window frames which were single glazed. The frames had come apart through age so I removed them one by one, took out the glass and nails, stripped, repaired and refastened with a good resin glue and dowels. The glazing units can be made up to a variety of thicknesses but building regs does specify a recommended width and depending on sill height you will have to have toughened glass, from 20 to 28mm. Once I had removed all the old putty, glazing nails etc it was then a question of routing out the frame for the addition depth needed for the glazing units. Quite simple to do with a half inch router and a sharp straight cutter finishing the corners with a chisel. The frames were then reassembled with new hinges and then the new glazing units, in this case 24mm put in with silicon and some wood beading that I had specially cut. No putty was used as from previous experience the small birds just ate it!
It was undoubtedly a lengthy process but rewarding when you saw the completed job. These were large windows which suited the house and matched all the others. And yes a labour of love and a good upgrade from single glazing.
Regards

 

[Doug71]

I generally avoid making windows these days because of all the regs, I find it's a hassle making one offs and proving they meet part L and part Q of the regs ( don't think part Q will apply in your situation). Some inspectors aren't bothered but others want all the details.

I don't use the slim double glazing very often, it used to have a bad reputation for breaking down, I don't know if they have improved the design or if it was just bad installation. You shouldn't use linseed oil putty with DG as it sets hard and DG need to be able to move a bit, it probably also affects the edge sealant.

If you create a log in on the Mumford and Wood site you can view all their drawings and sections they use which can be helpful

https://www.mumfordwood.com/

 

[Fitzroy]

I generally avoid making windows these days because of all the regs, I find it's a hassle making one offs and proving they meet part L and part Q of the regs ( don't think part Q will apply in your situation). Some inspectors aren't bothered but others want all the details.

I don't use the slim double glazing very often, it used to have a bad reputation for breaking down, I don't know if they have improved the design or if it was just bad installation. You shouldn't use linseed oil putty with DG as it sets hard and DG need to be able to move a bit, it probably also affects the edge sealant.

If you create a log in on the Mumford and Wood site you can view all their drawings and sections they use which can be helpful

https://www.mumfordwood.com/

Fab, I’d seen these guys before and looked at the sections and then lost the website name in my head. Great to have it back, and favourited now!

 

[Ollie78]

Thanks for this Ollie. Good to know I’m not obliged to go supersized thickness to cater for 10mm dgu’s. I’m planning on boarding the outer walls with the insulated stuff so if I make new sashes I don’t mind going a bit wider, but not so much as to look odd. I’m not in a conservation area… So I’m wondering if becoming Fensa certified myself is the get out clause from having to deal with council inspectors

Fensa is a scam and not relevant for restoration work anyway. Don't give them your money.

Ollie

 

[Ollie78]

What makes you say this?

Experience, I worked for a company who used putty for a while and it caused no end of problems.
Birds eat it, it can't be painted straight away even when dusted properly, it shrinks, and it dries too hard and is prone to crack.

The DGU manufacturers state not to use linseed oil putty and won't warrenty them. And if you really must they say first you must completely encapsulate all the edges with silicone. However, paint hates silicone so I refuse to use it.
The solution is hybrid polymers like Dryseal, Timbaglaze or Hodgesons heritage putty.
Solves all the problems, looks like putty rather than beads which have their own problems.

Ollie