Outsourcing for electricity

Kyle and I are both having to learn a lot of new things to pursue this project. We quite enjoy that part, but there comes a point where we simply don't have time to learn everything we need to. One of the most significant areas was electrical wiring and solar panels. This is a big, sometimes complicated area that we knew very little about to start with (by very little I mean high school science level of understanding, enough to figure out where the cables need to go but not which parts to buy). The learning curve is not insurmountable, but the time it would take would mean there are other things we can't learn that we need to. Just like money, and building materials, and space, time is a resource we have to budget for.

So we're outsourcing for the electrical wiring. Not necessarily to a professional electrician (though we know we legally have to have one to do any 240V wiring), but to my Dad who has kindly offered to help. Dad had to learn all about solar panels and wiring when he built a motorhome a few years ago, which he and my Mum drove from Malaysia to Scotland and back (for real - go check it out). So he has a fair bit of experience with solar systems (though a bit smaller than the system we'll have), and how to repair them when something goes bung and you can't just drop down to the store for parts.

At some point we'll get Dad to do a guest post about it all, because we don't know very much about it yet (we're getting Dad to do it so we don't have to spend time learning just yet).

The arrival of the bags

We ordered our woven polypropelene tubing from the Bundaberg Bag Company, who were the only supplier we could find in Australia that would confidently sell us tubes instead of bags. A quick look through their facebook page shows someone from their end has been involved in a few international build projects - I'm not entirely sure, but the water tank they built in Vanuatu back in April looks a lot like the one featured in a "how to build an earthbag water tank" instructable I found a while back.

The tubing comes in two sizes, 460mm and 350mm. Rolls are 1000m long. I ran the maths as best I could, and I came up with 4x 30kL water tanks at just a smidge less than 1000m. That was cutting it a bit fine for my rough calculations, so we decided to get two rolls of the 460mm as it's best to do water tank walls tick. This way, we'll easily get 4 water tanks and have some left over for experimental practice and the lower levels of the house. We'll probably end up getting another roll of the narrower stuff for the house build, as the upper levels of the dome can be narrow and the lower levels wider, but that's later on.

All up, including delivery from Bundaberg to Canberra, it cost us around $1400. We messed around with the idea of having it all delivered to my parents place in Brisbane and getting them to bring it when they come, but it turned out not to be a huge difference in shipping costs.

Composting toilet block

One of the first things we want on the property (after our symbolic veggie patch) is a toilet. Seems a no brainer to have a composting toilet, as we'll need to plant lots of trees in a few year's time. This is distinct from the smaller loveable-loo model we hope to have in our house - this structure has not been recognised by the council, though so far as I can tell it's in a legal grey area, and it's for the lead up to and during the build rather than while we're living there (though no doubt it will continue to come in handy into the future).

We've drawn great inspiration from Milkwood Permaculture's 'most loveable loo in the west' with bin specifics, amongst other various people who've done what looks to be about the same thing. We love Milkwood - whenever we decide we need to work out how to do something (build an outdoor composting toilet block, for instance), we set forth onto the Great Interwebs and seem to end up on their blog looking at exactly what we wanted. Essentially, two wheelie bins sitting under a corrugated iron shed of varying fanciness.

My initial (very rough) concept drawings give you a bit of an idea:

The patch of ground where we want to put the toilets is sloped down to the north, so we thought we'd take advantage of the slope to take some height off the building. The bins will be on the northern downhill side, so the chimney for the vents has lots of sun to heat it up and encourage air flow and the ground is naturally lower anyway. Entry will be from the south, up the hill a bit. There will be a retaining wall along the middle of the block, that the bins will butt up against when under the building. That way we don't have to create flooring that supports people's weight, we'll just use pavers from the tip to make a solid, level floor at two different levels (one for the bins to sit on, one for the people to walk on).

Since we have the space, and we're building a structure anyway, we figured we'd make each 'cubicle' big enough that someone could comfortably get changed in them, and have a bit of space for storage of things like extra toilet rolls.

We prepared the bins late one night, just before the shipping container was due to arrive as we knew we'd need them pretty soon.

...

We've got taps on the sides rather than at the back, as the taps protrude a long way and I was worried they'd get knocked on the ground as the bin is being wheeled around if they were on the back. Vents are on the opposite side as that works well with what the chimney for the vents will be doing. We did two bins this first time around, one left hand sides one right hand sides. The bins cost us about $130 each to make up, most of that being the bin itself at $95 from the local big-chain hardware store. We made some expensive choices on things like tap fittings as we want them to last, and we went out of our way to get black coloured bins, but the rest came from the tip.

Out at the property the next day we took the bins along and laid out where we wanted them to go. We'd measured them of course, and had a rough idea of the size of the building, but wanted to mark it out on the slope itself as we didn't have a measurement for that.

We put the bins in place, then sunk star pickets along where the wall above them will go and where the retaining wall will go. Then we cleared the grass from that spot. You can see my pitiful little section on the left being rapidly overrun by Kyle's on the right - he's a lot faster at this bit than I am. In my defence, though, it's not quite as pitiful as it looks in this picture as post of it's hidden by grass in the bottom left of the photograph.

Accuracy didn't matter too much at this stage, as it's just to have grass-free space to sink the retaining wall and the posts that will form the structure onto which everything else will cling. The posts are the point at which proper measurements and making sure things are really square starts to matter. The grass doesn't care if it's square or not, and the star pickets are just our guide for where we needed to clear.

Clearing grass is hard work, but satisfying. Took us about an hour and a half for this bit, with frequent brief stops to check the rain that was looking a bit threatening on the horizon and the nearby cows that were becoming accustomed to our presence and getting a bit curious.

A few days later we returned to lay the retaining wall. We reluctantly bought two new sleepers after failing to find anything suitable at the tip a few weeks in a row. We dug out the downhill section of our little bare square, and settled the sleepers in place.

Then, we dug three post holes. Kyle had already cut the notches for lap joints in the posts. After much discussion we decided to piece the beam together into the lap joints and fix them in place (square) with brackets before we set the concrete to hold the posts upright. This worked quite well, as there were only two of us and we didn't have enough hands to hold everything in place otherwise and make sure it was all square.

 

We lay drainage tubing on the earthen side of the retaining wall for good measure, then started sinking the downhill posts as well. These were a bit easier, and we ended up doing them one at a time but held in place by a few star pickets sunk into the grass and tied with rope. We hadn't wanted to do this for the middle ones, as it would have meant disturbing our nice firm ground with star pickets just after we'd dug holes for posts.

We ended up with these a bit off square anyway, though not an insurmountable problem. We learned from this and fixed our methods a bit on the other side. Of course, being interrupted by a hail storm doesn't help much - all of this took place over several days.

Once all the posts were concreted in, Kyle got a bit hammer-happy and put up bracing on all the walls. This will be what we screw the corrugated iron wall cladding to later.

At this stage we have 8 out of the 9 posts in (we would have had all of them, except for our hail storm interruption) and all of the structural cross beams are in. The next step is getting the roof beams on, then attaching the corrugated iron walls and roof ($50 at the tip for a big stack of it, what a find). After that it's things like seats, probably some shelves inside, and finding a source of sawdust.

Waterless Composting Toilet approval

I've mentioned previously that Kyle and I are pretty keen to go with a waterless composting toilet. We've done a lot of research and concluded that building our own is the easiest/cheapest/most reliable path for us to take to get there. We know that for an owner-built model NSW Health does not need to approve our system (this used to be required, but as of 2006 ammendment to the rules, and a later complete regulatory update, NSW Health delegates authority to the local council to approve so long as you aren't manufacturing them). We also know that most people in Australia who have built something similar haven't sought council approval. This isn't an option for us, as details of waste management are required as part of the development application for the house so if we don't succeed with this we'll have to put in a septic system and flushing loo's, which would be a shame. But it means we don't have much to go on about how to actually get it approved.

The Council hadn't had an application for an owner-built WCT before and weren't sure what kind of paperwork to ask for, so we politely suggested we might use the guidelines from the original regulation (from back in 1997) and see how that went.

Given the Council's unsure-but-game attitude we figure there's then a little bit of pressure on us to dot our i's and cross our t's so we don't muck it up for anyone else who wants to do this in the future. If Council has a good experience this time around, and are confident of our ability to avoid risk to the public health, they'll be more likely to look favourably on such applications in future. To that end, I've prepared what I hope is a very thorough application for a Waterless Composting Toilet.

Firstly, what is even required in such an application? According to the old rules:

1. Plans and Specifications for the proposed WCT (details of which are specified further)
2. Householder's Reference Manual outlining installation/operation/maintenance/trouble-shooting (the contents of this are specified further)
3. Placard with basic instructions to be hung on the wall next to the WCT
4. "Any further information required by the Council" (they haven't yet asked for anything in particular)

After initial approval, there's a process of inspections every few years as well (more forms and money to be paid).

What we wanted to do in the beginning was simply get approval to use a Jenkins-style loveable loo. However, the regulations specifically state that owner-built models must be the owner's own design, and that the health department is aware there are plans available on the internet. So really, if you want someone else to design it for you you have to buy an officially registered model. Since the only officially registered model that even approaches the functional simplicity and published evidentiary basis of Jenkins version is over $900 (which is more than double what it will cost for us to apply for approval and build the thing anyway), and then you have to order specially designed extra buckets on top, we decided to push ahead with a more 'original' version. I've done a lot of research, and have spent a lot of time trying to walk a delicate borderline between existing models that are evidenced to work well (being totally original strikes me as a fundamentally bad idea for this kind of thing) and designing for our particular circumstances and environment as the regulations require.

So, this is what we're sending:

For anyone reading this into the future, I will point out that you cannot use this document in Australia as the basis to put forward your own application (so far as I'm aware - specific local councils might have set up their own regulatory frameworks). The regulations are very specific that owner-built models must be of the owners own design, not simply plans downloaded off the internet (it states this in pretty much those words). This document is intended as an example, because that's exactly what would have been helpful to us to look at before we had to write our own.

At this point various people from the Council have already seen drafts of this document and offered advice, however this has not yet been approved. I've emphasised to everyone we've spoken to that we want to get this right, and whilst we've done our homework and are committed to this pathway we understand there are good reasons why regulations exist and aren't seeking to sit outside of them, just trying to find our way through them. Whilst it's often taken a long time to get answers from them (quite understandable as the questions we're asking aren't exactly run-of-the-mill) they've been reasonably helpful about it all.

I'll post a follow-up when we find out one way or another letting everyone know what the official Council response is.

Reclaiming Timber

We've spent almost every weekend for the past 2 years or so at the local tip - there's a shop attached, where they sell on anything that looks vaguely reusable for dirt cheap. This weeks tip finds included two large rolls of barbed wire, an assortment of tools/hinges/other odds and ends, and a collection of hardwood beams that all matched. $40 for the lot was pretty good.

The wood had a lot of nails still in it, but as they were all sort of sticking out a bit we figured we'd just spend an afternoon pulling them out before we do anything with them.

It's a bit tough at first, but once you get the hang of it it's sort of meditative. There's a big sense of triumph when you finally pull out a really tough one. And then you get to play silly games, like who pulls the nail that's bent the most (awarded today to the below offender who was the source of at least 20 minutes frustration), and guessing "what was this all used for originally anyway?" (we suspect someone's deck).

And then there are some nails that are buried deep, and surprise you when they finally get hammered out by being screws after all.

Express delivery of fresh manure

We discovered yesterday, after the shipping container had arrived and we went to check on our veggie patch, that the surprise cows had politely done a cow pat in the middle.

That's a pretty top-notch express delivery service, I reckon. We're going to try and track down who owns said cows and see if they'll just leave them there for a bit, as it's really quite handy.

Shipping containers

Yesterday our long-awaited shipping container arrived. This was quite exciting, as now we can store tools and building materials on site out of the weather rather than having to cart everything back and forth and unload the car a gazillion times.

We arrived a little while before the truck, and were a bit surprised to find about 30 cows and a handful of very small calves on the property.

We suspect they're the same cows that were in the next paddock over a few days ago that looked at us suspiciously when we were digging our veggie patch. We don't mind at all that they're there - in fact we'd been having discussions on and off for weeks about who we would need to talk to to arrange to borrow some cows or sheep. You see, the grass is getting quite long, and whilst my dad very kindly offered to lend us his ride-on lawn mower that seems like such a waste! We could certainly use it to cut down paths or rough driveways, but mow an entire 25 acre block? It'd take a week and way too much fuel to bother with.

Unfortunately, the cows were comfortably settled right on top of the spot we'd left our concrete blocks the other day, which we needed to go under the shipping container. So Kyle had to chase them off down the hill, poor dears.

The truck with our shipping container arrived right on time - apparently there aren't any problems with the 5km or so of unsealed road, though we had extensive phone conversations with the driver beforehand giving directions and making sure he was well aware of the road conditions and the layout of the property.

We talked through where the truck could reasonably get to without sliding or hitting rocks (not very far, it turns out, as the ground gets a little soft as you get further into the property).

I'd had a very amusing (for me at least) conversation with the person in the office that does the ordering for the containers - she kept insisting I had to think carefully about which way they had to load the container onto the truck. We had to, apparently, make sure we'd measured the space we wanted it to go and ensure the doors had space to open. If they didn't, we had to rethink. I said I thought we'd be ok either way, but she was very insistent that it trips up a lot of people. Nice of her to check I guess.

While the container was dangling a little on the crane we rushed around to the corners and put a concrete block under each one. We got these from the tip a few days ago for about $2 (for 10 of them - love the tip!).

Top tip - check that the doors open and close properly before the truck leaves. Our spot isn't entirely level (just a little bit off) and we didn't want it to cause the container to twist and make the doors impossible to open. This would be hard to fix later without the crane.

Of course the first thing we did after the truck left was do a little happy dance and put stuff inside.

It's very dark, though, so we'll need to get some lights with magnets to clip to the walls we think.

The container itself is a 40-foot high-cube - we figured if we were going to the trouble of getting one we may as well get the biggest we could find, as if we went smaller and regretted it it's hard to change. Cost a bit less than $4500 AUD all up, including delivery (about $1400). We went with the mid-level model - they have brand new ones, which were expensive, 'cargo worthy' ones which are old and rusty, then the mid level is basically the cargo worthy ones cleaned up a bit and given a fresh coat of paint. The one bit that wasn't really painted was the wooden flooring, so Kyle will go over that with some very basic paint before we really start to fill it to make sure it lasts for a few years.

I got quotes from every shipping container supplier I could find on the internet (about 10 different companies could deliver to our area). We ended up going through Port Container Services. For price these guys ended up around about the middle of the various quotes we got, but were extremely pleasant to deal with.

A few colleagues of mine have had very negative experiences with getting shipping containers delivered, from various other companies - issues with delivery time confusion, miscommunications, etc. We were very keen for this to go smoothly, as our window for when delivery could occur was very narrow (we wanted it right at the start of our two weeks off work, so we'd be there when it came but could make the most of it while we're on leave). Port were very lovely, everything went exactly as they said it would, and they were very clear about every step of the way. The only thing that was a little different was it showed up with no lock box, but looking back over my quote requests with them I requested a lock box on every other quote I got but theirs, so totally my fault not theirs and it's not really a big deal.

In the spirit of a happy relationship with the council we did check we are allowed a shipping container, and they did confirm this was fine so long as it was 10m from a boundary .

Work begins!

This weekend was the beginning of two weeks off work for both Kyle and I. Two weeks of what we hope will lead to basic infrastructure on the property.

Most of Saturday was spent shopping (heavy duty pants, welding visors, lots of stuff from the tip), during which we resist the feeling that we are haemorrhaging money and try to remind ourselves that this is what we spent so long saving up for anyway.

Sunday was a trip to the site. We knew we weren't going to get very much done on this trip (the first when we actually own the place - we took a brief trip out a day before settlement and did some blackberry clearing, but we figure that doesn't really count). The purpose was really to talk over what happens next and get a better feel for the place. Early on we realised you can't really skimp on the time you spend talking it over before you start - a constant process of revisiting and reclarifying and making sure you both have the same vision in your heads and the same idea of what steps happen when.

So, we explored a bit first...

There are several areas we have started calling wombat villages:

But also lots of smaller holes here and there that are probably echidna's, or various other burrowing crawlies:

There's also one particular tree on the far side of the creek that had three birds nests:

Last time we were at the property the creek had obviously flooded a little while before, up perhaps a metre or two. I've checked the weather data and it looks like it floods that much quite regularly but the catchment area isn't big enough for it ever to go higher.

The water is quite clear, though, and trickles pleasently:

We went further up the hill on the other side of the creek than we have before - technically the property boundary is the creek itself, but when the property was subdivided from the very large cattle station surrounding it the creek was too hard to fence so they put it on the top of the ridge. This means we have an extra 20m or so all along the creek of very steep south facing slope with lots of scrubby trees. So we went all the way up to the ridge to take a look along the fence line.

We found evidence of past bushfires, though obviously from quite a while ago:

There's a quite lovely spot with a bit mossy rock in the shade:

And the inevitable two or three spots with a large thicket of blackberries - this one is clinging around some large rocks, and it looks like some of the wombats have made tunnels through it to get to burrows underneath. Kyle tentatively leaned over the edge to take a look from the top:

At the top of the ridge we looked out over the neighbours property, a little greener than ours as it had obviously been grazed whereas ours has had the grass dry out over winter then regrow so it looks a bit brown from a distance.

Then we stood in the middle of the ridge and looked back up at our place. You can see a bunch of trees at the top, but only 3 of them are actually on our property.

After exploring we had an extensive discussion about what we want to achieve over the next two weeks. We've talked a fair bit about this before, but it's different when you're standing there and can see the scale of it and where things will go.

We bought some stakes with flags on from the tip shop ages ago, thinking they'd be useful one day, so we staked out where our outdoor kitchen will go (this is where we'll build the barrel oven). It will have a roof over the top, but otherwise be quite basic, at least to start with. You can just see the brightly coloured flags in the picture below. We've put it beside one of the trees right at the top of the hill, as we think that's a nice spot for entertaining - you can see pretty much everything from there.

A somewhat less definitely permanent composting toilet block will go a little way over on the other side of the tree.

Then we really got to work. We wanted the first thing we build on the property to be a little veggie patch. Nothing big enough to distract us from the build for the moment, but just something to say "we've started" and to begin as we mean to go on.

We staked it out pretty basic, with a few bits of wood we had lying around from ages ago that weren't going to be used for anything else much. We cleared the grass, and turned over the soil:

The neighbouring cows were fairly suspicious of us at first - they had lots of calves among the herd, and all gathered together staring at us. But eventually they got used to us, dismissing us as just odd humans I suspect.

So, first days work and we have a veggie patch!

A long way to go, but we definitely feel like we've started now!

Settlement Day

We are now officially the new owners of 25 acres of grassy hillside, and a rather sensibly sized mortgage. We're pretty chuffed about this!

And, as a bonus, we found out on Saturday when we went for our pre-settlement inspection that we have several resident echidna's in the immediate area. Here's a close-up of one we passed trundling up the road about 500m from our driveway:

He wasn't feeling very photogenic at the time. We saw another one a little later down by the creek. So now we have confirmed echidna's, wombats, kangaroos, blue-tongued lizards, native bees, and possibly a platypus!

Grey water plans

Reusing our grey water on the garden is a no brainer in our situation. However, for the purposes of being thorough and establishing what assumptions/constraints lead us to that conclusion let's unpack that a bit. For any new dwelling Council's require details of how 'waste' is to be managed on the property. What they usually mean by this is "pay us several hundred $ to connect to the sewers". Since we have no intention of connecting to sewers (they're miles away for a start, but also we'll have composting toilets so why bother?) we are left with the issue of how to manage greywater. Given the effort we'll go to to catch and store water for drinking, it makes sense to be just as strategic about where it goes to next.

We are aware that by and large most grey water systems do not 'save water' overall. That's ok with us, as our goal for the system is the strategic use of what would otherwise be waste in a situation where we have little alternative. Anywhere we go from just letting our waste water trickle down the hillside is a positive.

So, how? Our requirements for any system are generally that it's cheap, complies with regulations (usually the hard part), and can be made and maintained by us with minimal help.

In our initial meeting with the council it was obvious that their opinion of grey water reuse systems was less than positive. Extremely reluctant, I would say, certainly not enthusiastic. Grey water was the one aspect of this build that has been met with the most reluctance, on every other aspect of our project the people we've spoken to in the Council have been hesitantly open-minded. But with grey water, the boom gates really came down. It wasn't an outright 'no', but they were very clear that we'd have to have our documents very much in order to get this through. It does make us wonder what has happened to make this Council so reluctant to deal with grey water systems. We'll probably never know, but we can hope that we'll be part of turning that attitude around.

Firstly, the regulations. In NSW greywater diversion systems can be installed without needing council approval provided they comply with certain conditions which we won't meet. Local council approval is needed for a diversion system from bathroom/laundry - so far as I can tell the same SepticSafe form we'll need for our composting toilet applies to any proposed waste water system, with the section below listing the expected supporting documentation:

And they say Australia is an over-regulated society...

For kitchen waste water the story is a little different. We'll need a treatment system that is accredited. This was where the plot went from thickening to curdling for me. The Australian Standards make it very clear that local governments are not permitted to approve grey water treatment systems that are not accredited by the Health Department. However, I keep finding accounts of people who have managed to get various systems approved by council even when they aren't accredited, either just by that particular State's department or at all. It does seem, though, that for this first house project a DIY grey water treatment system may be one battle too far.

On my search for an accredited system I had a few requirements. Early searches found many systems with pumps and vent fans and all sorts of other contraptions that required electricity to run, this seemed like a completely unnecessary strain on our electrical system. I also found any number of systems that retailed for upwards of $10,000. Since this is almost half of what we hope our entire house will cost to build it, again, seemed an entirely unnecessary waste. Any system we choose will be simple and cheap. The third requirement is for limited maintenance. The various systems on offer that require a registered plumber to service them every 3 months are, to me, completely foolish and to be avoided at all costs. If we can't maintain it ourselves we're not really interested.

After quite a bit of searching I found a useful table that confirmed a lot of what I'd read already - that two particular models (EcoDesign's Greywater Reuse System, and EcoFlow's Nature Clear GWS10) fit the brief in being on the cheaper side, needing no electricity and limited maintenance, and had the added bonus of producing compost periodically. Seemed perfect, except they're both only accredited in Qld and 'parts of NSW'. We'll try our luck, I think.

One final note: We are aware we are designing a system that will not be able to handle substantial contamination with human waste. We also know we want kids somewhere in our future. This will inevitably lead us to a choice, down the track, about nappies that has a bit more weight to it than the convenience vs environment dichotomy that plagues most of our friends. Though a quick search found these, which would appear to solve the problem.

Water tank plans

We decided some time ago that it would be a good idea to build water tanks out of earthbags. Plastic or steel are expensive, concrete is just too much work. Plus, it gives us a chance to practice. The plan is to build water tanks over weekends, get water delivered to the site, then we can use that water during the main build (it won't rain enough between then and now).

For houses not connected to mains water the minimum on-site storage capacity that the council will approve in connection with a dwelling is 110,000L (90,000L for domestic use, 20,000L dedicated fire-fighting supply). As in, they will not approve a dwelling that includes a smaller water storage capacity. We asked, but apparently the lower demand for water resulting from use of waterless toilets doesn't count towards the mandatory capacity, so we still need to put in massive tanks. Realistically we know this is only a good thing, and we'd want to do it anyway, it's just a bummer to have to do it now.

First we had to work out how big they should be. It makes logical sense to want smaller tanks instead of one big one. Materials and so on come out a bit more expensive, but it means you can do maintenance on one while still having water storage in the other. I triple-checked with the Council and apparently on land zoned RU1 (which we are) above-ground tanks of any size count as exempt development, meaning you do not need to apply for council approval for them (in most other zones you need approval if it's bigger than 10kL). This stumped me a bit initially, as it didn't make sense that we needed extensive engineering consultations for the house, but the water tank (bigger, heavier, severe consequences if something goes wrong and multiple kL of water go rolling down the hill) is good to go regardless.

So we went through a process of working out whether to worry about that. We are aware of quite a number of 15-20kL tanks made from earthbags in various parts of the world. This proves the concept works, but what about a bigger tank? Will an increase in the diameter of the tank increase the outward pressure of the water on the walls? At first, logically, it seems like it should. More water = more pressure, surely? In a water tank we're primarily concerned with hydrostatic pressure (because the water isn't moving, so the only force we need to worry about is gravity). Pressure is related to the depth of the water, not simply the volume. The parts of the tank wall closer to the bottom will receive more pressure than the parts of the wall closer to the top, but the wall at the same depth doesn't receive different pressure if the volume of water is greater. So if we have a 2m tall tank that is 3m diameter, and a 2m tall tank that is 6m diameter, the pressure on the tank walls is the same even though the volume of water is greater.

Greater water depth = greater pressure, regardless of volume

(this is why people put water tanks on stilts, to get higher water pressure)

The next part to think about is the hoop stress on the walls. Hoop stress is the pressure perpendicular to the axis of a cylinder (so the walls of our tanks), and is related to both the radius and the thickness of the walls. Physics textbooks usually use the example of the pressure on the hoops of a wine barrel (I'm pretty sure that's where hoop stress gets its name). This is where it got hard for us, no one we found had done studies on the maximum hoop stress earthbags walls can withstand. After some very extensive internetting (including some excellent spreadsheets for materials calculation covering all potential water tank materials except earthbags) we realised that this was simply unknowable for us. Someone, someday, might conduct the stress tolerance testing to figure this out, but it won't be us. Given that, it follows logically that the safest approach is to ensure we use the widest possible bags (as hoop stress is related to both radius and thickness of the walls - to be safe within the unknown, maximise wall thickness).

Finally we wanted to thought experiment with what would happen if we were wrong and it all fell apart. There is potential for cracks to form in the tank wall over time, which would be a problem if we were sealing it with concrete and painted sealant. So we're going down the path of a tank liner instead. We think it is a reasonable assumption, though, that if the tank walls did start to fail this would be a very slow process over time and we would be able to monitor it as the tanks age. It seems likely that points where pipes fit into the walls of the tank are the weak points, rather than the structure of the wall itself, and any failure is likely to come from the fittings first. If we do notice the wall beginning to bulge outwards with time we can look into ratchets and strapping and see how we go, but again this is likely to be a process taking years rather than giving way overnight. As a bit of additional structural support, during construction we will use a trick I've seen in a few accounts of earthbag building, particularly in earthquake zones, where metre-long lengths of rebar are hammered down through the wall at regular intervals.

So, we have a bit of leeway with tank size from a structural perspective. Therefore, it comes down to convenience and cost. Given we need 90kL drinking water all up, we end up with the option of 2x 45kL tank or 3x30kL tanks. We also need at least a 20kL tank for fire-fighting water.

Kyle, who by virtue of having a more happy-go-lucky approach to life than ever-practical me, is in charge of ensuring we don't go too fast with this whole project and forget to have fun. In an effort to make his contribution to the water tanks he's suggested we should put crenelations on top and paint the sides to look like stonework. He reasons that since we have to have a bunch of big, round, tower-like structures anyway we might as well make them look cool. We met at the local historical re-enactment society, so this isn't an entirely left-of-field suggestion.

With this in mind, plus practical considerations such as the time it takes to build each tank, we think we'll go with a total of 4x 30kL tanks. My rough maths (aided greatly by Google's cylinder calculator - just google 'volume of a cylinder') tells me that a tank that is 2m tall will need an internal diameter of 4.4m to hold 30kL. Note that the height here is not the total height of the tank but the height to the overflow, as the roof (and any crenelations, if Kyle convinces me this is a good idea) will be a little higher by necessity.

Overall, dealing with the water tanks first is a good move. It will allow us to try out the whole earthbag concept in terms of materials calculations and get the hang of how it will work on site with groups of people doing stuff before we get to the complicated part (cylinders are pretty straight forward). That way, when we get to the house, we're familiar with the process. At least, that's the theory - we'll see over the next few months how that turns out in practice.

My budget hesitantly puts material costs for the build of each tank at around $1500 (including earthbags, tank liner, and fittings), but I'll go into further detail on that once it's a more precise estimate. I suspect our strategy will be to build one or two, then build the house, then do the rest at the ever indefinite 'later'.

The Property

Today we exchanged contracts on the property, after many delays caused by excessive paperwork in the system. We're now officially committed to this crazy idea. No backing out, no changing our minds - we'll just have to make a go of it!

The property itself is 25 acres of grassy slope, facing almost due north (very slightly to the east), in a (relatively) high rainfall rainfall area just outside of the town of Braidwood in NSW, Australia. The commute to work in Canberra will be just over an hour each way (an hour was what we considered our upper limit when looking for a block, though over time we hope to shift to working more from home/part time).

There's somewhere between 5 and 15km of unsealed road before the gate, depending which direction you come in from. The driveway itself is unsealed, and had quite a few weeds sticking up the first time we went there.

It's one thing to see '25 acres' written down on paper and quite another to walk it. We knew this was a problem for us going in to a property search, having been city kids we really had little concept of the scale, but thought it would be quickly solved once we were actually there. It wasn't with this one, as the property is almost completely treeless (nothing to give a sense of scale) and the hills are such that there's no one place you can stand and see all 4 corners (or even just opposite fences).

The view is very nice though - we think it looks better from a bit further down the hill. I've always been quite critical of people who buy a nice block then build a house right at the top of the hill, thinking "you're going to die in a fire" (I'm not being malicious with this thought, just commenting on the fact that so many people seem to prioritise scenery over bushfire safety in a country that's rather prone to fires). We like that our view looks nicer from further down, which is where we'd choose to build the main house anyway. Plus we intend to plant lots of trees so things will look different over time anyway.

At the bottom of the hill it flattens out again for a bit, before a small but apparently permanent creek.

The creek is just a little too wide to comfortably jump across. At some stage we'll build a little bridge, I guess. Perhaps a flying fox? It's easy to dream big when the work to get it done is so far ahead of us.

There are a few small patches of what looks like blackberries by the creek - they've clearly been sprayed before and are only just growing back, so we'll progressively rip them out.

When we went back to visit a few weeks after this first time, to confirm we still actually liked the place before committing to purchase, we saw something poke it's nose out of a small burrow at the edge of the creek. It could have been anything really, but we think it was furry rather than scaled and prefer to hope it's a platypus rather than admit it's probably a rat. We've also seen a very respectably sized lizard, probably a blue tongue, sunning itself by the creek.

We've seen a fox every time we've been there, so one of our first tasks will probably be to remove said fox. As sweet as it looks it is destined to become an ex-fox long before it has the chance to threaten our chickens/ducks or, more importantly, possible platypus.

There are, however, wombats.

There's probably twenty or so burrows in the hillside, all down by the creek and none at all further up. We know that wombats can be destructive to anything put in the way of their habitual pathways, so we figure we'll have to find out if these burrows are still active then build our pathways around the wombats habits. We'll see how we go.

The far side of the creek is a much steeper hill. Technically the property boundary is the creek itself, but it's difficult to fence a creek so when the property was created by subdivision the fence was put at the top of the hill opposite. In terms of agricultural land, this little section of no-mans land that we've incidentally acquired by virtue of the fence is not particularly useful as it faces almost entirely south. We won't be able to build any structures on it, but I thought that planted with a few things that will thrive in the shade it may be a good sheltered spot for bee hives or some such. Kyle's terribly phobic of wasps (for what I consider fairly good reasons on the basis of a very unfortunate prior experience involving a large angry swarm and a slow-moving cherry-picker) and finds bees a bit too similar for comfort, so the hives themselves will need to be out of the way a bit.

Not including the no-mans-land across the creek there are a grand total of 3 trees on the whole block. Looking back up the hill at them gives a little sense of the scale of the place.

Perhaps close-up helps a little more, for comparison?

We've got a good spot for the little house near the driveway up the top. Easy to get materials in, don't need the added expense of putting in extra driveway until later on, but a slight disadvantage regarding a head for water pressure from tanks. The big house will go in a nice hollow in the hill about a third of the way down the slope. There's no building envelope (set location where you have to build a house within the property) so we have free reign on where to build.

This property ticked off all of our requirements, plus a few of our 'not necessary, but nice' list:

• big enough for veggies + livestock of some sort + workshop + house(s) + whatever else we think of down the track
• building entitlement, prefer lack of established building envelope
• zoned appropriately for pigs if we want them later on
• gentle slope (for control of water flow across the site), preferably north/north-east facing (for good sunshine)
• few established trees (council's are fussy about cutting down trees, we prefer to be able to choose the type of vegetation on the property which we hope will grow to be extensive, so grassy was best)
• internet available by 3G/4G or fixed line (because we're tech-heads)
• max 1 hour commute to work (over time we'll lessen our commitment to work in the city)
• established dam, or potential dam sites
• (bonus) reasonable annual rainfall
• (bonus) electrical mains in the vicinity (just in case)
• (bonus) potentially abundant wildlife
• (deal-breaker) "feels right" (such an indefinable quality, but so necessary)

Initially we were looking for blocks under $200,000 - this one came in at just a bit over, but we like it so much we think it's worth it.

Settlement is officially the 14th of September. This is the day we will make the shift from the 'planning' stage to the 'doing' stage, and we expect the pace to speed up quite a lot from there.