I just received official notice from Council that I can go ahead and change the external cladding, without submitting any modification applications and having to pay fees.
I only have to provide a certificate of installation to make sure the new BAL Flame Zone cladding system is applied to manufacturer’s specs.
So it’s time to get quotes and look into some sexy Colorbond cladding to go over the firefly blanket system. As long as sexy is also cheap of course, the new matte finish steel won’t be in the budget.
I like the way they wrapped the steel around the corners in the photo of the build above, that’s a mighty fine way to deal with an edge. If I go with this cladding solution I’ll be using corrugations vertically as well to show off my 7m high mini-monolith of a house.
If you’re not sure what this has to do with the Tardis then check out the previous post. Time does not behave normally at Council, but at least they’ve delivered in the end and I’m not facing any more application delays to warp my mind.
The wheels have not fallen off, not by a long shot, but they did get a bit wobbly this week. Before you read on, this is a technical post about wall structure and cladding, so if you have something better to do with your weekend like a good book, a movie, or maybe watching grass grow then carry on with that. If you are interested in the nitty gritty then read on, but be warned, you might need to sit down with a gin and tonic at the end of this lot like I did.
I have put a moody mountains picture up the top of this blog post because it calms me, and reminds me why I am doing this. The project is progressing but I’d really like to get my DA in SOON.
Optimist that I am, I have been carrying on thinking that I have at least two options for my wall structure to meet BAL Flame Zone compliance. This week they both became a lot less certain, and probably more expensive. Darn you Flame Zone, darn you.
Option 1 bites the dust; well that’s a bit melodramatic, Option 1 bent down and tasted the dust and stood back up again, thinking about whether or not it would like to spend more time with the dust. After getting the NASH standard wall structure info (see previous post) I sent that to the company I am hoping will do my container build, and they said no worries we can build anything you want if you provide the specs, and something like that should only add about $2K to the cost of your build. Yes, $2K! So I thought right, we’re on.
The company has been amazingly helpful so far with such an out of the box build and a hundred emails and calls from me, and they are pretty busy developing a lot of cool new off-grid container homes. I’m fairly sure in this case they didn’t actually take a look at the NASH wall extract I sent before replying to my email in such an encouraging way, because when I then sent them the full house design and asked for a quote using that NASH wall structure, the first wheel went wobbly.
They recommended that I stay with the polyurethane spray foam insulation that they use as standard, because not only is it really effective, it also reduces the risk of condensation happening. Condensation can be an issue with the corrugated container steel if the corrugation gaps aren’t all filled by insulation. Normal flat batts are not so good. There might also be an issue with the type of internal framing they would have to add in to support the NASH wall structure in a container.
I can see their point but from what I have found so far, polyurethane foam is organic and therefore considered potentially combustible, so will not meet BAL FZ requirements. I am yet to see a BAL FZ approved wall system that doesn’t use mineral or glasswool insulation.
The condensation is also a risk but I reckon (being the builder architect that I am, NOT) that risk would be greatly reduced because of the thermal barrier in the NASH wall. Condensation happens due to the difference between the inside air temperature and the outside temperature – like if you sit in a vehicle with the heater on in winter and the windows up, and it fogs up the glass and drips moisture (not so much in these modern days with the aircon on though as that removes condensation).
So if, from the inside of the house to the outside, you had just plasterboard then normal flat insulation batts then corrugated steel then the risk of condensation, and therefore corrosion of the steel, is high in extreme temperatures. Like the temperatures you get in winter in the upper Blue Mountains; warm heated house inside, minus 2 outside. However, the NASH wall system has from the inside to the outside; plasterboard, insulation, plasterboard, 20mm air gap (air is a good insulator), then the steel. So I am guessing/hoping the condensation risk would be far less as the temperature difference by the time you get to the steel would be minimal.
Maybe you could also drill tiny, less than 2mm holes in the bottom of the steel wall to allow more air mixing – but small enough not to allow ember attack because as we know from BAL FZ, embers grow up to be bigger than 2mm.
So this wall system is not written off yet, it’s just a matter of whether the container builders can adapt it to a container wall system, and how much it will cost. The walls would also end up being about 130mm thick, which is a bit of extra space to lose in an already tight space.
Option 2, INEX cladding. The magic silver bullet that, in my starry eyed optimistic state, looked like it was a standalone BAL FZ cladding solution. A silver-bullet-proof werewolf caught this bullet in it’s teeth and spat it back out. Being a tough little bullet it’s only partly damaged by the wolf’s teeth so maybe I can still use it, but it lost a lot of its sparkle.
Reading the INEX specs for use in bushfire zones it says “No fireproof plasterboard required” and that it gives FRL 60/60/60, double that required for BAL FZ. I really wanted that to mean that all you needed was the INEX cladding to meet BAL FZ requirements, without any other wall layers.
My bad. As with everything in BAL FZ, the INEX weatherboard was tested as a system, and that system included R 2.5 rockwool or glasswool insulation underneath it. So adding the INEX cladding onto a steel wall with polyurethane foam insulation under that will not match the approved BAL FZ specs.
An option here is looking at how much it will cost to add the insulation to the outside of the steel under the INEX, instead of having the poylurethane foam on the inside. And looking at the relative cost of this compared to other solutions. If it’s affordable, that would make for thinner walls inside the container and a bit more space.
So, I am back to getting some more quotes and information on feasibility from the experts, and we’ll see what the best and most affordable option is. A tent with a heater is looking pretty good at this stage. I miss my block of land, the view I don’t get to sit and look at yet, and the cool fresh mountain air.
Patience, persistence…and a bit more persistence…and some stubbornness for spice ; the essential recipe for building a container home in a Flame Zone. Mix thoroughly and roast slowly over the flames.
With a footprint of around 60 square meters, my container house concept is pretty close to meeting the criteria for the “Tiny House Movement”. The values behind the design are definitely shared – realising that we don’t need as much space as we think, and using space in a more efficient way. Then there are the advantages of not having to heat and cool a large space, consuming less energy and less “stuff” in general (having nowhere to put it helps), and, critically, not having to clean a crazy number of bathrooms.
Seriously, how many toilets does a person need? And how much time do we spend in there each day? If your health and diet are OK, it’s likely that for most of the time the bathroom is just dead space.
Reducing debt around home ownership is also a major factor, avoiding a mortgage trap and being able to maintain freedom. I have to admit I am addicted to freedom. In my case the BAL Flame Zone issue is blowing the budget out a little, but hopefully not much and certainly not anywhere near as much as it would for a traditional home.
Small does not necessarily mean plain though and given the lovely private block of land that I am very fortunate to have, this design process is all about letting the outside in. Letting in the light and the view, but not the bushfires.
So here is a draft design, consisting of 3 forty foot containers, two on the bottom and one on the top. I am new to SketchUp so please forgive errors, lack of details, yada yada. My floor plan is looking much neater than this 3D effort. I have left in the default SketchUp dude for scale, in his bomber jacket with clipboard.
Imagine a classy finish inside, timber feature wall, wood stove with corrugated iron backing, and nicer furniture (no offence SketchUp). Plus a railing around the deck of course.
In this design the living space works out to be about 5m x 4.7m which is not a bad amount of space. I now carry my tape measure with me everywhere I go and my friends and family are getting used to me randomly measuring bits of their houses.
I have offset the bottom containers a bit so that the design is not just a plain box, but also so that I can put in a dining nook and tuck the dining table out of the way. I don’t use my dining table much, and the nook will also function as a cosy book reading spot, or an alternative office space where I can put my feet up and work on my laptop. Under the seat will be storage space.
To open up the space a bit more, the floor of the 2nd story container is cut away over the living/dining area below, so there is a double height ceiling in that section. That still allows for a good sized room in the rest of the top floor container, which then opens up onto a rooftop deck via glass doors. These will be high cube containers so with insulated ceilings should still give about 2.5m in ceiling height. That’s a crazy 5m high ceiling section, pretty cool no? While I’m not into dead space from extra toilets, dead space from high ceilings and extra light I love. There has to be somewhere for artworks and a feature wall too, and this space has lots of potential.
The stairs leading up to the 2nd story loft are in the kitchen, and are looking very dodgy in the drawing (sorry about that, no time to draw each stair and no idea how!). The stairs will have a pantry cupboard housed underneath and maybe a pull out bench for extra work space in the kitchen. Sorry Harry Potter no room for you.
The 2nd story container is pending DA approval of course, but hopefully the roof top deck will stay put either way. It would be a tragedy not to be able to sit on top of the house, drink in the view and do a bit of twitching arm-chair style (that’s bird watching for anyone who thinks that twitching sounds unhealthy).
I am meeting a surveyor on site this week to get my landscape plan underway. Once that is done, along with concept drawings of the house and steel-based wall structure etc, it will be time to chat to the RFS about whether the overall design concept is OK for BAL Flame Zone, and also chat to Council about the design in general and clearing of the block. At least it’s a very small footprint to have to clear.
I haven’t found the pot of gold at the end of the rainbow yet, but I have at least found the start of the rainbow. External steel clad walls can exist in a Flame Zone. You may well ask, how can steel cladding and pretty rainbows be related? If you are not sure then you need to read my previous post first.
I heard back from NASH today (National Association of Steel-Framed Housing Inc) and they have new NASH Bushfire Standards coming out at the end of this month. There is a solution for using metal clad walls in BAL Flame Zone in it!
Little dance of joy.
Little. NSW Rural Fire Service don’t accept the NASH Standards for Flame Zone as a standalone, but might as part of a total solution – which according to NASH seems to mean that if you have water tanks dedicated for fire fighting, have AS 3959 rated windows and satisfy other aspects of the AS 3939 conditions, then the wall solution should be OK.
One key issue with steel in a BAL FZ is that steel is a conductor (although not as much as some other metals) so it would conduct some of the the radiant heat expected in the Flame Zone. There is potentially a LOT of radiant heat in a Flame Zone. The NASH solution therefore has a “thermal shield” in it, which going by the diagram looks like steel battens that create a small air gap between the steel and then an extra internal layer of plasterboard, creating a plasterboard sandwich on the inside of the steel (with insulation in the middle). A pic taken from the new NASH standards is below:
To me this looks a lot better than having to put plasterboard, membrane then fibre cement over the outside of the steel, and would have a smaller carbon footprint than all those extra layers. I am yet to cost it out.
I also don’t know how tricky or expensive this is to apply to a container build yet, as it has implications for insulation (normally spray foam) and also structure (achieving the gap between steel and floor frame for example). The full NASH document might include some other solutions, who knows. It’s a good start!
Thank you NASH. I had no idea you even existed until this week, but you are my favourite acronym now.
Sometimes it’s great when you are the first to do something, sometimes it is not. I am really hoping someone else has used steel walls in a BAL Flame Zone, in NSW.
I have spent many hours interrogating Lord Google and writing to steel production companies, design forums that promote steel cladding, and a few builders and architects. It seems that these days according to AS 3959, Superman should have been the man of fibre cement, or 90mm thick brick.
However, there is a bit of potentially, slightly good news at the end of this week’s investigations.
I was very excited to find this steel and shipping container building in what looks a lot like a BAL Flame Zone (pictured above). But, that was not the good news. My tail stopped wagging when I found out from the architect that it is a temporary structure so it didn’t have to have a DA. I have since found mention of another steel building in a BAL FZ in NSW, although it mentions fibre cement as well, so I am hoping to hear back from the builder or architect from that project.
Then I boldly ventured further into the world of bushfire industry acronyms and bureaucracy. The best news so far has come from the CSIRO. I came across a study that tested a steel building against the flame zone standards (AS 1530.8.2.) – the roof and floor did well, the walls needed a bit more work (doh!). Then I found a more recent conference paper that ran some more tests on steel walls, and I contacted the lead author at CSIRO who was really helpful. He said that “there are a number of new provisions relating to steel construction specified by the NASH building standard which have been recently adopted into the BCA”. This translates to the National Association of Steel-framed Housing, whose building standards have been taken up by the Building Code of Australia.
In short, with the right insulation and internal wall construction, he reckons it should be possible to achieve BAL FZ with steel walls.
That is where the real fun started – the BCA is not meant to be read by normal people. I got to page thirteen thousand and something only to find I did not have the right amendment version. There appear to be lots of amendment documents and they all come up on Google as “BCA 1996”, rather than the year of the actual amendment. I am assuming that the 13th Amendment didn’t happen in 1996, if so someone did a really bad job on the original BCA.
I think the new provisions happened in 2013 or more recently, so have been trying to find the correct bit of the BCA. Well, I’m not now, I’ve written to NASH instead, the BCA can go jump in the lake because I don’t have 200 hours a week to spend on this. I would rather be picking out nice colours for the interior…assuming there will be an exterior at some stage to keep them in.
The other potential cost blow-out is the BAL FZ windows, which may require extremely expensive kryptonite-resistant glass and shutters. However, I found a helpful forum which seems to suggest that in NSW there is an exclusion on Clauses (e) and (f) of 3.7 in AS 3959. “Yipeeee” I thought, not knowing what the heck that meant but liking the sound of exclusions. What it means is that using BAL 40 twice (windows and shutters) might equal BAL FZ. More on that later. I am meeting a bushfire assessment consultant on site later this week and have a growing list of questions that I hope he can answer…
I realised I haven’t given many details yet – so before someone sensible points out that you can’t just dump a container on a block and live in it “because it will get hot” – I thought I should say that this is a proper build in the making. It will be fully insulated to normal housing standards, lined with plasterboard, plumbed and wired to Australian Building Standards etc.
If you’d like to see an example of a seriously stylish container build, check out this link, the photo above is from a design by Benjamin Garcia Saxe. This is one design that I am considering as a base, along with a couple of others.
Right now I am on a learning curve and in discussions with container home builders for the structural part of the build, structural engineers for foundations, and crane drivers for feasibility of delivering containers to the part of the block I want the house on. But that is all side issue stuff for now, the real meat in the sandwich is the bushfire assessment. The site is at the very top of a steep forested gully, which makes it a ring in for Bushfire Attack Level Flame Zone (BAL FZ) – the nastiest classification you can have. Well done me. I guess that comes with a lovely block in the middle of the bush with a bit of a view.
So the important conversations are with Bushfire Assessment consultants. There is a lot to consider to comply with AS 3959 – it’s pretty scary that I can already write that Australian Standard down without having to look up the number, along with AS 1530.8.2 (and if you’re after general FZ information it starts on page 74 of AS 3959).
One of the most challenging issues so far is the corten steel walls that come with shipping containers. This is strong stuff, built for being at sea for 25 years or so and taking a battering. Container builders say it’s fire proof, which is logical being steel and all, but for BAL FZ that’s not enough; materials either have to be non-combustible and 90mm thick, or have a Flame Resistance Level (FRL) of 30/30/30, or comply with AS 1530.8.2 – which involves someone spending a huge amount of money for CSIRO laboratory testing of the material when exposed to incredibly high temperatures and flames. No-one has tested corten steel. Blue Scope steel says that no steel is ever fire tested and it’s all about having steel as part of a wall system, but they only have a tested “system” for roofs, not walls.
Blue Mountains City Council have been very helpful so far, and I have a copy of an approved DA for another container home in the area that has not been built yet. That one is clad in a fibre cement system, in fact it has three layers outside of the corten steel – special 16mm fire resistant plasterboard, membrane then 6mm fibre cement sheets.
Understandably Council says that someone needs to put their money where their mouth is and prove that corten meets some sort of building standard. Steels are not all alike, and many a shed has buckled under a bushfire – integrity after a fire as well as flame resistance is part of the rating system. So I am trying to find any information that will support using steel panels, corten alone or even with weathered steel cladding over it, as the outer part of an external wall in BAL FZ.