Hard wood double glazing + glazed units

3 Apr 2004
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United Kingdom
Hello, I am in the process of having hard wood replacement windows and have noticed that the glazed units are not kite marked and do not have a British Standard mark, the company are telling me that the units only need it if its saftey glass, is this correct?

Also I have a large set of French doors that have glass panels of 2' 6" by 5 ' 10 " each and these glazed units are 4 6 4 mm because the company say its that size because its a wood door and because of the weight, but I do not see what difference in weight a 4 16 4 glazed unit is going to make which is what the other windows are. The door units have a kite mark but no British standard markings and does not appear to be K glass.

Any advice please. Next time I will go for good old UPVC do not look as good but less hassle.
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window glass does not need to be toughened (safety) so kitemark/bs not ness unless over a specific size.

K glass is by special order only and you have to specify it at time of ordering, I think it's about 20% dearer. If you dont know, K glass has nothing to do with strength, just heat loss.

It is quite common I believe for for patio door glazed units to still be 464 on wooden doors.. The weight does have a factor, but more importantly, if they make the unit wider the rebate has to be huge, which then compromises the strength of the doors. With the size of glas it is a LOT of weight, and can easily cause the doors to drop. Some companies (such as magnets) do use 4/12/4 though.
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It's not so much the size but the position. According to the Building Regs. if the bottom of the window is less than 800mm above the floor or if it is next to a door or if it is in a door then it needs to be safety glass. This could be toughened or laminated or very thick annealed.

Your windows are unlikely to meet Part-L of the Regs. without using a low-e glass such as Pilkington K and argon fill.

The weight of a 4-6-4 unit and a 4-16-4 unit is the same (the space is not very heavy even when filled with argon!). Your French doors should also meet the insulation standard since more than half their area is glazed. And they must be either laminated or toughened glass. 4mm of annealed glass would certainly not be strong enough to meet the Building Regs. If the weight is too much for the door it really is not a well made door. Oak is stronger than PVC so please don't blame the material. A two inch thick door can accomadate a 24mm unit.

Pilkington K glass is often supplied with a little orange sticker telling you which side should be facing indoors - but your supplier may have removed this. You can just about see the difference. Under direct sunlight there is a very feint bluish tint to the glass surface. (Soft coat low-e glass does not have this.)

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