Vertical separation of openings in external walls

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Type A buildings require protection for vertically separated openings in external walls. This video steps through NCC requirements found in C2.6.

Transcript

C2.6. WTF. Where's the fire resistance? C2.6 is a part of the BCA which requires an FRL and sometimes buildings are going up without it. Now I didn't see this particular building under construction so I'm not saying that this building doesn't comply. In fact there's clues that tell me that this building likely does comply with C2.6.

The reason I've shown a photo of this building is that it nicely shows some things about C2.6. Some might be thinking, "What's C2.6 again?" C2.6 is vertical separation of openings in external walls. Part of Volume One. It applies to all Type A buildings, like the unit building I showed you just now, and it's the reason why we have spandrels and other construction to prevent fire from spreading from storey to storey, which is directly related to Performance Requirement CP2. I'll step you through each part of the provision right now.

This is sub-clause (a). The first paragraph, the lead in, tells us we need to worry about separating openings when our window, or other opening, in the external wall is above another opening in the storey below, if its vertical projection falls within 450 millimetres of the lower opening. What does that look like? Here's a simple example, we have a three storey building, we'll make it Type A for this exercise. The openings are shown by the blue boxes; A, B and C. B is directly above C, so we have to worry about protecting those openings from one another, because if a fire broke out of opening C, we don't want that fire spreading to opening B. A is not directly above B.

But we have to consider the vertical projection of A, which is shown by the dotted line. If the distance of that vertical projection is more than 450 millimetres from opening B, then it’s okay, no protection is required. However, if that distance is 450 millimetres or less, then we need to provide protection between B and A. So if we have to provide vertical separation, the various options are given in sub-clauses Roman 1 to Roman 4. In short, it's going to look like an FRL of 60/60/60 either vertically, that's options one to three, or, horizontally, that's option four.

The Guide is quite helpful on this topic, and steps through these options. On the left we have the spandrel approach, Roman one, where the total height of the spandrel has to be at least 900 millimetres, and at least 600 millimetres of that has to be above the floor. You can have all 900 above the floor if you want, only you can't have less than 600 above floor level. Or you could use the horizontal projection, where the 60/60/60 FRL extends away from the wall, and at least 450 millimetres either side of the opening. So what does this look like in real life?

Like I said, this building is very helpful, it shows both examples. First, it shows the horizontal projection. We have these balconies, with big sliding doors. The sliding doors are openings in the external wall above one another, so protection is required. And these balconies will provide that protection so long as they extend at least 1100 millimetres out, and at least 450 millimetres either side of the opening. Balconies like this one make great horizontal projections, but something we need to be careful of is all the holes that end up in balconies.

We need to be sure that the holes don't compromise the FRL. These balconies here have light fittings installed, there's probably a conduit in the slab. It's likely that the slab still achieves the FRL despite the conduit, but it is something to something to check. Balconies often get holes in them for drainage or even downpipes. If possible, these holes should be located away from the area that provides protection, else you need to look at protecting those openings say with fire collars.

We also have these windows to the right of the image which need a spandrel because there's no horizontal projection. That looks like fibre-cement cladding to me, which typically doesn't have an FRL. So we need to install a spandrel. That will look like FRL 60/60/60 construction behind the cladding as indicated in red. But here's the thing. Those windows aren't the only openings.

Have a look at sub-clause (c) of C2.6. C2.6 isn't just about windows and balcony doors. As far as this provision is concerned, anything that doesn't have an FRL of 60/60/60 or more is an opening. So this building will have to have an FRL 60/60/60 in a spandrel, 900 millimetres tall, at least as shown here. Most of the walls are rendered, presumably there's blockwork behind, so it is likely that the whole wall easily achieves the 60 minutes.

Where we have to be careful are these feature clad walls, the 60 minute spandrel has to be behind that cladding, it could be the whole wall or just a 900 millimetre tall detail. I didn't see this building under construction, so I don't know what it used. As far as I know this building does comply with the NCC. But often this requirement is overlooked, so that is why I'm bringing it to your attention today. I've shown you C2.6(a), which outlines the different ways of achieving construction, that need protection.

I've also shown you sub-clause (c) which shows us that everything is an opening if it doesn't have an FRL of 60/60/60. What I've skipped over is (b), but I'll show that to you now. These are the exemptions when you don't have to worry about providing a spandrel or horizontal construction. Of course, you don't have to worry about Type B and Type C buildings, this only applies to Type A buildings. And you don't need to protect openings in your open-deck carpark or your open spectator stand. Your sprinkler protected building, though note that the FPAA101D and 101H systems don't enjoy this concession.

You also don't need to protect openings in the same stairway, and you don't need to protect openings where the floor between the storeys doesn't need an integrity or insulation rating in its FRL. Otherwise, this applies to the external walls of all Type A buildings of all classifications. So don't just check the floor plans, check the elevations as well!

Otherwise you might end up with a problem like this one. This building isn't in Australia. It's a residential flat building in London, and this fire happened last year. You can see the damage to the building just the right of the centre of this photograph. There are a number of factors that caused the fire to spread in this building, including the combustible cladding but notice that each balcony has an opening which has been damaged by fire.

Those balconies aren't concrete; they're steel framed. And had they had been constructed to provide horizontal protection in accordance with C2.6 which admittedly doesn't apply in London, I'm sure that there would have been a lot less damage, if this building did have concrete balconies constructed in accordance with C2.6.

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