Triple glazing and weight

[Kelvin]

We have specced 3G for our build. There is one large slider that the timber kit company has said is a problem due to the size of it, so much so they suggested not to triple glaze it. However, I’ve insisted and they’ve agreed albeit they had to seek approval from the factory (Nordan) They’ve not been specific about the issues triple glazing this window will cause other than difficulty fitting it on-site. 
 

On Friday I had a call with the MD of the kit company about several other issues I have. In passing he mentioned the 3G weight problem suggesting it might need the glass installing on-site and it creates a challenge for the frame so might need extra strengthening. I think I am being prepared for a massive cost increase which I’ll find out tomorrow. 
 

Fitting the glazing unit on-site doesn’t sound ideal to me. Is this common for very heavy windows? After watching Grand Designs for years with their enormous 3G windows being craned over rooftops I am surprised it’s such an issue. 
 

The window (W02) is 5mx2.1m although I believe the small window at the right side of the slider is separate. 
 

 

 

[markc]

At that size I would fit the frame, get it all true, fixed and ready then lift the glass

[ProDave]

Well certainly lift the sliding part out, then you halve the weight to lift frame plus fixed pane.  I know ours is smaller (3M wide total) but we lifted that with 4 blokes and 4 sets of suckers. Then lifted the sliding part in.

[Radian]

Our 6m slider frame came with the sliding sections pre-hung but with the 2G glazing units separate. Just three other guys and me walked the frame into position, and I only really got in the way 😄 I wouldn't have thought the metal frame would take the necessary handling loads if it was all pre-fitted with doors and glazing? 

Edited October 9, 2022 by Radian

[Kelvin]

Ok so it’s not unusual for the IGU to be separate and fitted on site. I’ll make a note to scrutinise it for edge damage before fitting 😂 

[MJNewton]

I expect the additional rigidity of ‘pre-glazing’ helps minimise stresses and strains on the corners of the frames whilst being transported and lifted into place.
 

 If 3G makes the entire unit too heavy to do this then perhaps they’re worried about the open frame by itself. If this is the case though there must surely be ways they can brace it - even just temporarily with timber.

[MJNewton]

Just now, Kelvin said:

Ok so it’s not unusual for the IGU to be separate and fitted on site. I’ll make a note to scrutinise it for edge damage before fitting

Completely normal. Remember they’ll have come from a completely different factory and so all you’re doing is marrying them up later in the cycle by doing it on site.

[Kelvin]

The big slider features in half their designs and we can’t be the first people to spec triple glazing so they must have dealt with it before. 

[JohnMo]

We don't have big sliders, but nearly all our windows had the frame installed first then the glazing.  Because of acces and weight.

[craig]

Standard practice, certain size require the sliders to be built on site and fixed sections glazed, others built but not glazed.

 

It’s generally a decision left to the suppliers and installers but likely that kit is being supplied with Nordan here.

 

Not an issue tbh and there shouldn’t be a cost to kit unless is has been spec’d minimally and not designed with a greater than weight requirement. The actual difference in weight  won’t be that much. Per m2 and per mm thickness glass will be 2.5Kg x 1, 2 or 3 sheets of glass (i.e single, double or triple).

 

4mm per m2 10Kg

6mm per m2 15Kg

8mm per m2 20Kg

Edited October 10, 2022 by craig

[Kelvin]

Thanks all. Very helpful. 

[Ralph]

We have two Rationel triple glazed sliders both 480cm wide and 208cm tall . Each came in two parts comprising of a two panel slider and a static window all glazed.

 

The two panel slider was 281Kg  and the static window was 145KG 

 

I may be misremembering but I don't think we took the sliding door out. Just man handled it plus a Manitou for the first floor one. 

 

 

 

[craig]

For anyone that needs it, here is a quick excel calculator you can use to calculate glass weights for double / triple. Most I would assume won't know this and therefor use your unit size, it will give you the approx. overall unit weight if you use it that way (give or take a couple of KG).

 

Some example data entered and I have purposely left out laminated as the difference is negligible imho.

 

 

glass weight calculator.xlsx

Edited October 11, 2022 by craig

[Kelvin]

Super. Thank you. 

[Kelvin]

Meeting with timber kit company today. Still not confirmed 3G is 100% possible. 🙄 How hard is it to get this confirmed. So frustrating. Said the window will need craned in. 

[craig]

Are they doing the install? What’s the site layout like? Won’t necessarily need craned in but they’ll be doing a risk assessment based install and need to submit RAMS etc.

 

9 out of 10 times a tele-handler and vacuum suckers are more than enough.

[Kelvin]

Yes they are doing the install, well their affiliated builder is. There’s a 3m level offset around the whole perimeter with good access onto the plot. However, the plot is on a slope so I can see getting it in a bit of a challenge. But that will also be the case if it’s double glazed. 
 

 

[Kelvin]

Thought I’d update this. After a lot of back and forth and goal post changing about why the kit company won’t install a 4m 3G slider, unless I take all the risk of it going wrong, we have reached a solution. The max weight of slider that they’ll install as one component is 350kg. Anything heavier and the IGU has to be installed separately which the kit company won’t do. Therefore, we’ve agreed to fit a 3.6m 3G slider (347kg) and change the coupling window from a 1m tilt and turn to a set of 1.4m French doors.