Ayres Rocks

A big, big milestone was reached today.

Today, we had Daniel from Geo Drill come out to the block and do the soil tests. So the first actual work to be done on the block that has meaning in this whole big adventure has been completed. Daniel drilled core samples for the slab engineering as well as setting percolation test holes for determining what sort of effluent disposal system we will be allowed to use.

Now we just need to wait on the engineers interpretations of the results to see if we need a complicated and expensive slab for the house, or if we’ll be able to get away with something that isn’t going to cause great financial pain.

We’re being billed for this as part of the engineering work so I don’t as yet have the full account. I expect it to be somewhere between $1600 and $1800.

After much debate between ourselves about the pros and cons of each of the methods outlined in Part 2 we have decided we are going with poured earth, for the following reasons.

Simplicity.
I can see Darren our draftsperson having a good ‘ole belly laugh at that one word appearing anywhere someone is talking about building. Poured earth is going to mean we can build the external walls and get the roof on without actually making any walling frames. While it won’t go up in 7-10 days like a shed would, here’s hoping to have a shell with a finished roof inside a month. That time frame is tight and is going to need a substantial window of great weather and material suppliers cooperating to deliver the windows, roof trussing and roofing steel on time as agreed.

Once we have the locked up shell, quality of life on site is going to be remarkably improved and everything will fall into place. Am I just dreaming? We’ll see if any of the project execution and planning skills I developed in a previous career can carry over to this, that is for sure.

Speed of Build.
This is so important. Being self employed (in a truly complicated way that does not tie our incomes directly or in its’ entirety to client interaction) the more time spent on the build is less time spent earning money. We’ve set a goal of 8 hours a day “on site” and 4 hours a night catching up with work. As weather and other unpredictables reduce building time we’ll use that to make up hours we should have been working on our businesses. Until we can borrow a caravan or camp under a roof we’ll have the highest tech tent campsite in the world

Aesthetics and Finish.
We’ve seen a couple of these projects both in the flesh and through the good souls in the owner builder world who were happy to share their projects with us. What can be achieved is exceptional, ranging from a real earthy looking appearance to something so close to sandstone you’d need to look twice to make sure it isn’t.

If we’re going to put in all that sweat equity we sure want something to sit back and admire every time we have the opportunity to do so.

Overall
Poured earth is going to give us the look we want and meet other criteria we had set long before poured earth was even an option we were prepared to consider.

Soil test for the foundations and footings are being organised. There will also be a percolation test done as we are not in an area serviced by main sewer and will need to install a septic system of some description. This same company will be asked to design the foundations and footings for the house and give me some pointers on footings for the shed as well. Once I’m happy with their service you know I’ll be happy to post their details on this blog.

Darren from Wise Drafting has been a great asset to our project. I’ve been firing off questions as we start to nail down details and he’s been firing back nicely detailed answers to help me make up my mind on aspects of the building.

When he sees the opportunity to involve some ideas I’m not aware of he fires off an email that explains the benefits along with links to the products for me to further look into. You have to appreciate someone with his attitude towards delivering us the best package he can and his willingness to set my thinking back on the right course.

I certainly appreciate his efforts and if you need a draftsperson who is a thinker and will give your project the best outcome, you should talk to Darren as well.

Wow, this was money well spent.

Darren met us, on time, at the Tungkillo pub before we finished the final trek out to the block. My wife and I were both impressed from the get go. I like it when people start talking about processes and ticking things off the to do list, then produce the list and start doing just that. To me that means there is thought behind the process that has led to refinement of the way he conducts his business. No BS, no vague references, just facts based on our answers to his questions off of that list. Everything gets covered.

Turns out our design was quite well suited to take advantage of passive solar principles. Standing on the block we were able to line up the orientation of the house. Darren was able to explain just what passive solar is and how the winter sun is able to be used with great advantage, conversely the summer sun is able to be kept at bay with clever use of shadow, even on the wall that will be facing straight into the morning sun. I feel the hours and hours of googling, reading and researching through owner builder magazines was now time very well spent.

We have exactly what we want and Darren can calculate sun angles and so on and tweak slight aspects of the design. This should end up giving us a home that is light, warm and comfortable during the winter and able to cope with the extremes of summer without monstrous cooling systems in place.

If you’re a South Aussie and looking for a clued in architectural draftsmen then I am happy to suggest you head on over to Wise Drafting Pty Ltd and see what Darren can do to help you into your dream.

As each job is individual, depending on complexity within the design, Darren prefers to quote each individual job. By using what we are paying as a guide you might be over or under estimating the cost for your job. Things like size of house, distance for him to travel for a site visit, 2 storey designs and so on all alter the quote. I’m therefore not going to specify his costs, instead you should contact him yourself and get a quote based on your own ideas.

I will however include his costs in some other large item, so rest assured the overall cost of this project will remain open for you to see.

Those that know me will not be surprised I’ve already read through and taken notes on all the relevant information from the back issues of The Owner Builder magazine. One thing has been confirmed in my mind, and that is building with earth makes more sense than anything else.

The question is now which method is going to provide the benefits we want. 
The Methods
At the risk of insulting those who make earth building their lives, there are perhaps 4 methods of earth building, although there is considerable overlap between all of them. Again, without offending those that make this their passion, here is my oversimplified version of how things work.

Mudbrick–  60% of the world lives in mudbrick dwellings. Unfired, sun dried clay bricks is what they are. In Australia they are now typically stabilised with cement, lime or organic emulsions mixed into the clay slurry to improve weathering resistance and improve their strength for load bearing applications.

Mudbricks can be puddled, requiring lots of space, plenty of molds and incredible stamina to mix and pour the bricks into the molds. The brick mix for puddling is extremely wet, allowing for a slow cure that produces a very strong brick.

Pressed bricks use less water but some sort of  pressure to activate the clay and stabilising agents in the brick to produce a brick that could be used immediately, or left to dry just as the puddling bricks are.
Both bricks may have straw incorporated into them to improve insulating efficiency and also to lighten the bricks weight. A traditional mudbrick made in Australia would weigh around 20 kilograms.

Mudbrick is also known as adobe which in my world means bloated software. I believe the word is a derivation of Spanish/Arabic for brick.

Rammed Earth– Large form works are bolted into place and filled about 600mm at a time with a mostly sand mix stabilised with concrete or lime before being compacted inside the form work.

Poured Earth – smaller individual forms more like molds are used and a wet mix, again mostly sand with some clay and cement or lime to stabilise, is poured into the mold. The pour is allowed to set overnight, the mold removed and the next layer of bricks is mixed and poured.

Light Earth– A clay slurry is mixed with straw or wood fibres until all the straw is coated in the clay. This is then pressed into wall frames often made from woven timber strips, or as a newer and less time consuming alternative, over light steel mesh. The clay protects the straw, the straw/fibres acts as both insulation and filler again reducing the weight

Costing each method
I don’t enjoy paying more for something than I see value in. This often leads me down the DIY path, and thankfully for our bank balance and the wife’s sanity I am not one of those “Tool Time Tim Taylor” DIY tragics. Therefore I would consider trying anything, but only after research, thinking, research, planning, research, consulting, research and research. My figures here are accurate for the quantities involved, I even added 10% to cover incidentals. There are ALWAYS incidentals.

Mudbrick – I have no problem with digging a dirty big hole, taking the soil and mixing it with a stabiliser before using an hydraulic press to press a brick.
Cost approximations –
1 x 40kg bag of cement per 40 bricks. 4660 bricks = 116 bags of cement @ $12.50 = $1450
$150 to weld 2 molds, 1 working, 1 spare.
$420 for a 20 ton hydraulic press and a lightweight steel mesh safety shield. 
$9000 for a shed to keep the entire process out of the weather.
So a realistic cost for doing mudbricks, made by ourselves, is $3, 000 without the shed. (I won’t get a shed with any of the other options below either. Realistically any of these methods need somewhere to securely store machinery out of the weather but for comaprisons sake lets ignore the shed).

Interestingly to have the bricks made and delivered would cost around $17,200!

Rammed Earth – Specialist work requiring a LOT of experienced labour and a LOT of expensive machinery. We would also need to import a lot of sharp sand to cut back the heavier clay soil we have on the property. I have not honestly costed this option, I can do rough sums in my head and know that 2x bobcats at $100 an hour for a fortnight and 4-6 labourers on site is more than I am prepared to spend on hired hands.

Poured Earth – This one is tricky. We have plenty of soil that will need cutting back with some sharp sand to produce a better sand to clay mix more suitable for this. The volume of walls we will need to make is 58 cubic metres ( not allowing for any window or door openings), lets do these figure on needing to import the full raw material on to site.
Steel for brick molds – $400
Ply for brick molds – $450
52 cubic metres of sharp sand – $2240 (yes only 52, there will be roughly 6 cubic metres of cement)
Cement, 161 bags @ $12.50 = $2020
Realistic cost for this would be somewhere around $5600.

This would let us form 40 bricks 600x300x300mm per day, or around 24 metres of wall. Hell it wouldn’t take long nor be expensive to build a poured earth shed would it? Edit – No, it wouldn’t, $2000 for walling materials.

Light Earth – I’m still trying to figure out why you would bother with this method. It requires a framed wall, lots of steel mesh and amazing amount of patience as you literally take a handful of clay and straw and force it into the mesh. I don’t like the method nor do I particularly like the finished result. Straw can be expensive, the material needs to be screeded, it takes forever with manual or mechanical labour to turn clay into a smooth slurry and the biggest downside for me is I doubt you’d get a load bearing wall made from this method without extensive frame work behind it.

Speed of build
Time is money is time. I and the wife are self employed, if we are working on the house we are not earning any money. Quite simple really. The quicker we can get our building to lockup the better.

Mudbrick – I’ve seen believable accounts (read that as not on the site of the manufacturer of these presses and molds) from people who were able to make 15 per hour with 2 people mixing, forming and pressing the bricks. So we would also need 310 hours, and I’m guessing an 8 hour shift will be physically demanding enough so around 40 days of really motivated effort (ahem) to produce all the bricks. Lets be real and say 60 days or 2 months.

The longer the bricks are allowed to dry the more dimensionally stable they will become and the less shrinkage and possible cracking will occur in the walls when built, so lets allow 3 months drying time.

The bricks will weigh 20-25kg each making for a lot of really hard labour when it comes to laying the little blighters. Accounts from experienced mudbrickers suggest 100 a day for 2 people, including mixing the earth mortar and laying and pointing the bricks. Add in incidentals like moving scaffolding as you go, hot and/or rainy days, your body telling you to GFY and I’d expect 2-3 months as a realistic time frame.

That adds up to 8 months, 5 of which can be expected to be back breaking labour.

Poured Earth – I own a petrol powered mixer that can comfortably mix .099 cubic metres per load. (The real amount a mixer can mix is not the full bowl capacity, which is what you buy them by. That load works out to 3.5 cubic feet and the mixer is rated as 5.5 cubic feet.)

Some stats based on the verified capacity of that mixer:
It would take 15 loads to fill each set of molds.
It takes 15 minutes to thoroughly mix each load, maybe a minute to shovel each load into the molds.
The perimeter wall of our house is 72 metres, we would need 9 courses in height. I have worked this out to be 20 days @ 5 hours per day of work allowing for window and door openings.

I would need about a day to create the mold system after having all ply and steel parts precision cut so they only need to be bolted and screwed or welded together. This is where eager retired parent and parents-in-law come in handy. Especially when they also have their own welders and know how to weld. I’ll rabbit on about the mold system and the design specs and manufacturing in another post, if and when it becomes a reality.

So we would need 3 weeks to a month to get the poured earth walls built. Here we have the luxury of doubling the mold system for relatively small cost. Either way that will double the capacity or turn our mix and pour days from half to full, halving the days required.

Rammed Earth and Light Earth – I have read rammed earth is still time consuming and I can’t even begin to guess how much walling can be made by a team of labourers in a day. Light earth, well as above why would you want to? Certainly not for me but I’m sure it has its time and place.

Well, originally
If you had asked me this question before we bought the block I was sure of the answer. Ranch design, 3 bedrooms and 2 bathrooms in the main house with 2 guest suites and their own bathrooms under the main roof but not accessible from the house. Overall building would have been a massive 40 metres long, 9 metres deep with 2.4 metre verandah all round.

It would have been a steel portal frame (shed) engineered to comply with BCA codes for Class 1 structures (houses). We would have a mish mash of colorbond panels, blueboard with murals, stone facings and all sorts of other ideas to detract from the overall look of a shed.

The idea was we spend little on the structure, which lets face it is there to keep the good stuff out of the weather, but lavishly fit out the inside with quality fittings and fixtures and skimp on nothing.

But then
We found this block, with all its undulating hills that plan was not workable. We spent some time re thinking our plans before we bought the block to see what we could do that would allow best view of the block from the main living areas of the house.

This switched our design to a 3 stage build.
Stage 1 was the “sleeping” block with 3 bedrooms, 2 baths, an office and a living are that would serve as the kitchen as we built stage 2.
Stage 2 was the “living” block, with large open combination family, dining and kitchen and a generous laundry and store room being the other 2 physical rooms in that building.
Stage 3 was to be the guest suites, complete with their own living areas and bathrooms.

This design was well suited because we could stagger the buildings up and down slopes and link them with decking and well sheltered breezeways. This idea was kyboshed after an informal discussion with the council planners as it was not in fitting with the rural aspect of the surrounding areas.

So then
Well, we had to rethink things yet again. The ranch style design was still the favoured of the 2 we had, so we took some careful measurements on the block and worked out we could fit a 27×9 metre building into a plateau on the block and stay within council prescribed developments by not having to excavate or fill past their stated limits.

While the 40 metre design just would not work, by dropping off the guest suites and removing the under main roof workshop and garaging, we has the best bits of the original ranch design in a size that would be able to be built on the flat area we had indentified.

But now
I’ve always had an interest in being “green” which means I knew the idea of the shed was the devil because the energy consumed in mining the ore right through to the delivery of the  finished product is enormous. This is called “embodied energy”. With that in mind we set out to see what we could build our house from that was more sympathetic to our green views.

Well, we have 58 hectares of Adelaide Hills land. If you know Adelaide you know the soils here are largely reactive clay. Our land is not as heavy in clay, and the soil would in fact be ideal for making mud bricks. Now we’re talking about technology used to build in the time before Jesus. The Great Wall of China is built from mudbricks, and it’s estimated 60% of the worlds population live in mudbrick dwellings.

Typically mudbricks are made in 2 ways –  by mixing the materials to make a very wet mix, or “puddling”  and by using a dryer mix compressed to form the brick. Puddling produces a stronger brick, but requires a lot more water and physical mixing as well as a larger area to allow the bricks to set in the molds. In both manufacturing processes the bricks are air dried rather than kiln fired as traditional clay bricks are.

By manufacturing myself a simple press made from a hydraulic ram and using  a 10-20mm plate steel mold, we can make our own bricks on site by mixing dampened clay soil with some medium such as straw and using a very small amount of lime or cement to stabilise the brick. Compressing the mix under high pressure will activate the bonding properties of the clay and lime (or cement) and form a solid brick. The brick can then be released from the mold and allowed to air dry.

Most of the energy in manufacturing a brick in this fashion is good old fashioned hard labour, making the embodied energy of either method extremely low.

So now
I need to find a draftsperson sympathetic to this old school approach to building and have a design drawn up that will use our mudbricks as load bearing walls. This also means I will need to produce several batches of bricks in different mix ratios and have them certified as being load bearing, which can then be passed on to an engineer who can then give the council the paperwork and computations they need to see to verify the structural integrity of our house.

Why load bearing? Then we don’t need to bother with building any sort of frame and will be able to bolt the roof trusses straight to a top plate built into the walls. Doing this cuts down on the amount of material we need to source and have brought on site, making our house greener by the minute.

The only immediate downfalls to making mudbricks on site are time needed, space needed for storage and the sheer mass of the bricks. At around 90 tons thats a lot to store, and will also mean a huge variation from normal for the slab design.

But then again
I’m not committing to the idea of building with mudbricks. It will take 3 months just to get bricks made, dried and certified then at least 6 months to make and dry the bricks we’d need for the house providing we pass certification.
The largest problem with building green is the time and money required to get things engineered and approved. It is still an infant industry and the technologies are just not widely enough used to make them cheap options. What someone on Tasmania has done can’t be translated to a site in Perth for example without the approval, testing and engineering process being done again to suit the Perth site.