Double glazed sash windows - Part L

[jetset]

Hi all

I'm new to this forum so...hello!

Does anyone know the sizes of the sections for sash windows that are to be double glazed to comply with the 'new' Part L? I need to know the size of the rebates for the d/g units.

I have the router cutters from Wealden that are used for 38mm sash material, producing the smallest flat ovolo profile. I'm thinking of using this same profile on 50mm material so that the larger rebates are possible.

Jim

[jfc]

Hi Jim and welcome .
I normally use 65mm x 50 mm sections if i can giving a chamfer of 15mm x 15mm and a rebate of 35mm x 15mm . I use a chamfer on the outside to look like putty and bead from the inside . If i dont have room on the sash then i go for 65 x 45 and try and go for a smaller bead to hold the glass in . It all gets a little tight .

[jetset]

Thanks jfc.

Do you mean 65mm side to side and 50mm between parting and staff beads?

Regards

Jim

[jfc]

Yup , you got it .

[dirtydeeds]

watch out if you are installing them in existing openings

in some cases you will need to put in a false internal wall otherwise the increased width if the sashes (meaning a wider box) will stick backwards into the room

[jonnyd]

HI you could go for 4/8/4 16mm Argon filled units to get a bit extra on the rebates.

Jon

[thatsnotafestool]

Is this a replacement or part of a 'new' build?

I like to see out of my windows as opposed to seeing 4metres thick of window frame (OK - I exagerate) so I got my BCO to waive the pointless regulations and agreed on 4-6-4 k glass.

[jfc]

Smaller units cost more money so you need to see how that cost off sets against thicker timber and packing out architraves . Roger is lucky as he agreed with the BCO that 4 6 4 would be fine but his property is one of a kind i think . Well it was untill he got hold of it ;D ;D ;D

[jetset]

Jun 2, 2008 18:24:17 GMT dirtydeeds said:

in some cases you will need to put in a false internal wall otherwise the increased width if the sashes (meaning a wider box) will stick backwards into the room

Excellent point.

I'm building an extension and the window is a new bedroom one as the extension will cover the old opening. There were two small casements before.

I found out today that the BCO won't bother about the double glazing in this old part of the house (but obviously will for the extension windows) so I'll go with single and make a box that will be the same as the one in the room below. The sashes in this property are from a nominal 38mm thickness. I've seen three nominal thicknesses of components on sale (in London): 38, 44 and 50. Does anyone know why there are three sizes and how they affect the brickwork, or rather, how the brickwork determines the sizes?

Regards

Jim

[thatsnotafestool]

Do you also have to make the windows fireman-friendly on an extension? I know that you do for a new build.

[jetset]

The extension is only a kitchen and bathroom so I don't think they have to be 'fireman friendly'.

Can anyone answer my question, above, about the sash section sizes of 38/44/50 and whey are these sizes? Is it the brickwork?

[jfc]

Yes , it's the depth of the rebate in the brick work . I have just made some windows for a loft conversion and both of those had to have the min fire escape opening ...550mm clear opening if i remember but check with regs on that one . Also the windows in the old part of the house do have to comply with regs its just you are allowed an extra 0.2 on the u value .

[jetset]

I see. What I don't get is for solid walls two brick skins deep, the rebate will be just one brick skin deep but you see three different sizes of sash for what appears to be the same thing.

[jfc]

Different build methods ? Clinker block , sand stone , brick , timber frame etc .

[jetset]

Sure, but I've seen all three sash sizes on double-skin solid walls in London Stock and wondered how that's possible. Do you think it's just the thinkness of the plaster finish or maybe the walls have a slight cavity with snapped headers?

Thanks for the responses btw!

[jfc]

I am also in London and have seen all three sizes . Not sure about 50mm i think it's 33mm 40mm and 45mm they stock or something around those sizes .
This is the first time i have really thought about it but it may have something to do with no cavity in some properties and then the older horse hair and lime plaster being thicker in others . I do know that they dont stock anything to take DG units that have been in the regs for five years

[mrgrimsdale]

33mm 40mm and 45mm would be ex 1 1/2, 1 3/4, 2, inch sawn. Almost everything I've done was 44ish. Sometimes down to 33. Rarely bigger e.g. ex 2 1/2 giving about 55.
9" walls may give a 5" or more rebate (brick actually more like 4 1/4 +plaster) so 1 1/2 would fit easily.
In any case if window fatter than the rebate you can build up a bit behind the architrave and you'd hardly notice.

cheers
Jacob

[jetset]

Yes they are the same sizes as I was quoting, only nominal/sawn ones, as opposed to finished/planed. The house I'm working on has the 1 1/2" material which is small and I hadn't seen it before.

Regards
Jim

[jfc]

I've been thinking about it some more and it seems to me that the thinner windows where used in the cheaper houses . I:E servents quaters and housing that is not so cheap nowadays . I know of a whole row of houses in Richmond that has the thinner sashes where built for manual workers .

[jetset]

Ah yes. Now that makes perfect sense. Many timber merchants (at least in London) sell these compenents for the sashes but they only sell the box sections pre-grooved for the 2" sashes.

I want to make the boxes for the smallest 1-1/2" sashes. Does anyone know the correct sizes for these and also the reveal from the brickwork outside? I'm thinking about 1" at the sides and top (assuming a straight -- not arched -- lintel.

[jfc]

What timber yards are selling pre grooved box section ? I make my own .

[jetset]

In South London, Merton Timber and Fulham Timber are two that I know of.

[jfc]

I think you are talking about sash stile section rather than the box frame section . I have a Merton timber in Twickenham and the said they stock the stile section . Matt has a supplier of the frame section , i must get the number from him .

[jetset]

Merton definitely sell the box section. Pulley sides back and front. I bought some from them last week.

[jfc]

Hmmmmm , there are some right tw*ts hired by timber yards now adays ! I will call again and see if i can speak to someone that knows what they stock