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UK glass regs

karlpallister

OK, so I'm a NooB - shoot me for that bit first...

Not sure how many on this site are based in the UK, but if there are some UK based people, is anyone having trouble with the ban on combustibles on high buildings, including the laminate in glass? As if a tiny layer of laminate inside the glass panels could contribute to fire-loading...

For a glass-sided balcony, how are you getting around this? Monolithic glass (despite the fact it isn't as safe)? Alternative materials?

Something about glass - it's cheap as chips, but looks reasonably classy in my view - win win apart from the fire issue

 
Nov 27, 20 12:04 pm
Non Sequitur

"As if a tiny layer of laminate inside the glass panels could contribute to fire-loading"

Apparently, it does.

Nov 27, 20 12:17 pm  · 
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Koww

afaik the ban has exceptions... e.g. office buildings not included

Nov 27, 20 3:46 pm  · 
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apscoradiales

karlpallister ,

I'm not sure how a 1 metre high glass railing along the edge of the balcony could or would stop flames from leaping over it and around it and prevent the upper levels of floors from catching fire.

So what difference does it make whether that glass is simply tempered/laminated or just simply tempered? The flames, particularly if wind driven, would ignite the upper floor without any problems no matter what kind of glass you have.

Now, if the balcony is cantilevered, as they usually are, and the flames move vertically across, and above the glass railing, what's going to burn on the balcony as many of them are constructed out of reinforced concrete, ie., non-combustible construction? Chairs, BBQ's...?

If the balcony is made from combustible construction (wood, for example), then it'll catch fire no matter what the railing is made from; tempered glass, tempered/laminated glass, steel, aluminium, wood...).

Assuming all along that you already have a 2 hour (or whatever) fire separation between different levels at the floor line.

Over here in Canada, we did (or still do?) a fire separation between floors. If the exterior walls are curtain walls, then we do a spandrel panel at the floor line - maybe 800mm high above the above floor, and maybe 800 mm also below that floor. That spandrel panel (glass and insulated metal pan) would then also have a fire rated gwb wall assembly (usually shaft wall construction) behind it so that fire could not easily leap around from one floor to another. Glass and the metal pan do not contribute to the fire resistance rating at all - it's all up to the gwb wall. Naturally, there is fire and smoke rating at the floor line between the edge of slab and the metal panel.

Does all this make sense or have I confused you?

Nov 28, 20 1:11 pm  · 
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apscoradiales

An Addendum...we would also do the spandrel panel/rated wall in "unprotected opening" scenario when a building is close to the property line or close to another building. This would stop fire from spreading from your building to another. Not much to do with glass and balcony issue, but it's good to know anyways.

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Non Sequitur

Aps, we don’t do the rated spandrel anymore unless you are dealing with spatial separation issues. The failure point of the AL frame is much less than the floor so there is little use of a rated spandrel. It think t laminate layer referenced above is not from a fire separation POV. I believe it is a combustible content issue similar to phenolic cores in laminate cladding.

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apscoradiales

I understand the issue the poster is addressing. It makes a reference to the Grenfell Tower fire.

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karlpallister

Thanks - some great points here. Yes, the ban spawned out of the Grenfell Tower fire, and there is a blanket ban on combustibles. This includes the laminate in glass, although it makes balcony guarding much safer than monolithic glass. I think the effective ban on laminate glass is an unintended consequence, but my question is really about how architects are getting around this in practice. What do architects use instead?

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apscoradiales

I don't know what's being done about it now in Canada. When I worked (retired now), we didn't have to worry about using tempered/laminated glazing on the balconies. Was never an issue at that time. I guess we can thank St. Gobain for screwing things up and making combustible sandwich panels, and the local architects/authorities/builders for negligence.

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Non Sequitur

Aps, laminated glass is a big issue in Ontario. Too many broken panes due to water freezing in the glazing shoes and clamps cause shards to rain down with previous types. I think even tempered, when used in interior applications, needs protective caps to prevent accidental breaking.

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apscoradiales

Non Sequitur,

I can't believe the code would restrict one in the use of laminated glass at balconies because it thinks the glue would melt and set the whole building on fire. That's ridiculous - political correctness of the code gone crazy, imo.

Why don't they then say, you must use steel frames, and break up the whole railing into pieces smaller than 1054 square inches (or whatever the hell it is for a 1.5/2 hr rated glass wall)? The glass railing sits on non-combustible  reinforced concrete balcony, and the flames are leaping around it and over it from the lower floor - how much will the adhesive contribute to the destruction of the building?

Where is Eric Esselink when you need him?!

Nov 28, 20 4:53 pm  · 
1  · 
karlpallister

Haha, my point in a nutshell. Of course, in the UK, metal balconies are much more widespread. You guys in NA haven't seen it much yet, still wedded to concrete, but I think the Energy Step Code and the movement to better thermal facade performance will change that

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apscoradiales

You have a code consultant? See Jensen Hughes code guys ...Ask them what the situation is with this. Are we all going to have to use steel or concrete railings?

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karlpallister

Yes, I have a contact at Jensen Hughes - thanks for the tip.

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apscoradiales

karlpallister,

Germans already have rebar that connects the concrete balcony slab to the floor structure and it provides for a thermal break of as much as 100mm. So, you jam some mineral fibre between the balcony and the floor slab, and that is much, much better than having the slab extend all the way out which would then cause condensation and icing to occur to underside of the floor slab.

Very clever those Germans.

Anyway, no need for steel balconies if you use this stuff.

Dec 1, 20 11:23 am  · 
1  · 
karlpallister

Yes - the Schoek thermal breaks are very good actually. Very widespread in Europe, not known anywhere near enough in NA.

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t a z

Facade design organizations in the UK are tracking changes to the relevant standards so industry groups are good place to start researching.

This free CWCT guidance document has regulation interpretations and a design flowchart which would be relevant to balcony guardrails (as a component of the facade design).

Have a look:

https://www.cwct.co.uk/pages/c...

Dec 1, 20 1:54 pm  · 
1  · 
karlpallister

This is a very good doc, and highlights exactly what I am posting about - didn't know it existed, so thanks for that.

The interpretation above highlights several inconsistencies in existing guidance regarding the use of laminated glass as part of the building envelope (external wall and specified attachments).
There are particular concerns regarding restrictions on the use of laminated glass in balustrades to balconies.
Glazing used in balustrades should not injure anyone who collides with it and should prevent anyone from falling. This generally means that it should be a safety glass and provide adequate containment.
One of the primary benefits associated with laminated glass is its post breakage behaviour. Monolithic glass offers little or no post breakage robustness, and when it breaks it can crack or shatter
into small or large pieces (depending on the temper state). The post breakage behaviour of glass is an important design consideration, especially where glass is used overhead or where it is providing a barrier which prevents persons from falling from height, and the relevant requirements K2 and K4 of the Building Regulations must be satisfied in addition to achieving fire safety.
Approved Document K in England refers to BS6180 for further guidance. BS6180 allows monolithic toughened glass to be used as a balustrade. This is an area where much of the industry has
significant concerns and have for many years recommended the use of laminated glass on safety grounds, therefore going beyond the minimum requirements set out in the Approved Document.
A glazed balustrade incorporating toughened monolithic glass provides no post breakage robustness. Once broken (for example due to inclusions even if heat soaked, or due to impact) the entire glass pane will shatter into small dice and may fall from its fixings depending on the method of retention and lateral loading. This presents two separate safety risks; firstly, the glass dice may fall in substantial clumps and can fall onto people below, and secondly the missing element of the balustrade presents an opening through which somebody could fall.
Glazed balustrades combining laminated glass with a robust fixing system provide a good level of post breakage robustness. Broken laminated glass will tend to remain in-situ as the broken layer (or
layers) of glass are held together by the interlayer and retained by the fixing system. The risk of falling glass is mitigated and no opening is created in the balustrade through which somebody could fall. The glass can be identified as being broken and can remain in place until such time as the replacement glass is installed.
Therefore, the only glazing that the industry considers as satisfying the requirements of Part K of the Building Regulations in a practical way in a balustrade is laminated glass. The current uncertainty about whether it is permitted under the changes to Regulation 7 effectively prevents the use of glazed balustrades in any residential building which is higher than 18m from ground level.
There is an urgent need for research to properly establish the fire safety of laminated glazing in balcony balustrades and to provide clear formal guidance on this topic.

So back to the original point now, I'm wondering what other architects are doing on current projects and whereas they may have used glass previously, they are now having to look at alternatives. 

Great shout on the CWCT guidance - thanks

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t a z

No problem!

The answer to your design question is much easier than code interpretation.

Check regional design and real estate (development) blogs to see what's been proposed for resi lately.  Any renders published recently would presumably attempt to be compliant under the latest regs.

dezeen is pretty UK centric but off-hand that's the only site that springs to mind.

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t a z

Not sure if this is a free download:

https://nla.london/insights/lo...

1  · 
apscoradiales

The answer?

Concrete and steel. Won't burn, though steel could melt under intense heat.

Stupid!!!

Dec 2, 20 9:26 am  · 
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Non Sequitur

^steel fails under heat... then it melts. 8-) The concrete cover thickness is what gives it protection. Pedandics aside, I don't think we have the same combustible material restrictions up here in regards to laminated glass. We certainly do in Ontario for composite panels (in buildings above 3 storeys) but laminated glass is the only acceptable glass for balconies. Anything else is too weak given our freeze-thaw cycles.

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apscoradiales

steel railings/balustrades...not rebar.

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