And your not going to see any of it!!!

Was the mantra that was repeated over and over by my labouring wife over several months of preparing the house site for the pouring of the slab. This is the last expensive thing we need to do before getting on with the relatively cheap mudbrick making. I really can't blame her it has been a bit of a slog but we can now see the end of this stage of the house build.

To ready the site for pouring the concrete slab it is simply a matter of digging the trenches, adding a layer of sand (road base?), boxing up, covering it in plastic and setting out the steel reinforcing. We have done these steps but of course we added an extra level of difficulty.

Firstly we put up the frame and roof before the slab, which is not normally the way it is done. The main reason we did it this way was to get the house build started quickly so that we would be able to extend our planning permit (ie. frame stage finished). It has had an advantage in that we don't have to worry so much about the weather when preparing for and when we eventually pour the concrete. But we have had to dig the trenches by hand (or pick, shovel and wheelbarrow), which added up to moving about 16m³ of dirt. This was done over a period of a month on the weekends. Because the outer edge is curved half the trenches ended up being curved. The total length of trench was about 160lm. The dirt we moved was dumped next to the house and will be used for the mudbricks and render later on.

The next step was covering the bits of land with about 8m³ of sand. This was done by wheelbarrow and shovel. We compressed the sand by hitting it with a bit of 4x2. The sand needs to be slightly wet to do this well, too dry and it won't hold it's shape, but too wet and it is too sticky.

The boxing up was also a bit different and I think a bit easier (and cheaper) than if we had a square slab. The entire outer edge of the slab is curved, so I decided to use 3ply because it is easy to bend instead of 6x2's that you would normally use. I used scraps of 4x2 and 3x2's upto about 500mm long to stake the 3ply. The bits of wood were staked to the ground with 250mm galvanized fencing nails (these will be re-used for fencing once the slab is done) and then the 3ply nailed to it. The slab is 150mm above the ground level so the 3ply was cut into 200mm strips. Because the 3ply is curved this adds strength to it and hopefully it will hold up on the day of the pour.

Laying the plastic we thought would be a bit of a nightmare seeing as how half the trenches are curved and at odd angles to each other and the added difficulty of working around posts. But it wasn't all that difficult and only took a day. We used about 400m² of plastic to cover an area of 200m², I guess it was in the up's and down's of the trench walls, the overlap of the plastic and a little extra in the trenches so when the concrete is poured it doesn't pull the edges in too much.

The last bit of the preparation really highlights one of the reasons most people don't make a round house. Trench mesh is straight and is really, really hard to curve. So we had about 80lm of straight trench which was easy to lay standard 3xL11TM in. The outer edge and inner trench which made up 80lm of curved trench needed to have 3xN12 bar, which is 12mm notched steel bar, which needed to be curved. This ended up being not too hard to do, but did add a lot of extra time over installing standard trench mesh. There also ended up being a lot of extra cutting of the slab mesh (SL82) because it has to follow the edge of the slab. We also had to navigate the 10 central posts and cut more than half the 18 6000mm x 2400mm sheets used to fit around the posts. But myself and the wife got the job done in about 4days with a bit of help from the kids.

So now we are ready bury the whole lot in about 40m³ of concrete, we just need to organise the concrete, concrete pump and helpers for the day.

Framed signed off (possibly), and a roof!

We did get the extra timber to finish off the frame and had it up in September. Some cross bracing was then added and all the bolts had to be tightened.

Once done we called the building inspector to come out and check the frame for sign-off. Because we used the coastal grey box which is rated pretty well instead of what the engineer specified in his documentation for the frame the inspector wanted the documentation changed to reflect what we used was in fact ok. For instance the engineers report specified for the main beams 2 290x35 nail laminated to make a 290x70 beam, We used a single 290x70 beam. The engineer also specified mostly F17 kiln dried hardwood, we used unseasoned coastal grey box which is rated to F22 unseasoned, but when it eventually dries it goes upto F34.

We have submitted the updated engineers report to the inspector but to date and after several attempts to check that the extra information was adequate we still don't know if we have the frame signed off, but taking a positive outlook on it and assuming that no news is good news we have moved onto the next step, the roof.

We got several quotes and finally settled on one from a local roofing company, a bonus is that the owner of the company lives just down the road and is a nice guy. One of the things that we did want is to either put the roof on our selves or at least be involved in putting the roof on. As owner builders we want to do as much as we can, the roof is one of those jobs that the authorities want a certificate for. The roofing company after some negotiation were happy to knock off some of the cost of the roof and let me take part as a general laborer.

In total it took 4 working days to complete the job, and there were three of us. Myself and two qualified roof plumbers. The guys did a great job of the roof even though they constantly made cracks about the wonky frame. We ended up putting on wire mesh, then foil with 50mm fiber insulation (fire proof, and an >R2 rating) and a "Surf mist" colourbond corrugated roof. We also got a round gutter (called smoothline) which looks great. The head roofer was in charge of cutting all the gutter joints and the roll top flashing. He did a fantastic job of lining up the flashing as you can see from the picture.

Now that the roof is on we have to save money up for the next big jobs, lining and insulating the underside of the roof and doing the slab (or maybe strip footings). While we save money we will start making mud bricks which will make up the inside walls, this is a relatively cheap job but pretty labour intensive.

The frame almost finished

The frame is almost finished now, and would have been finished if not for a change of plans. Originally when ordering the timber we were going to leave the two north facing outer segments without purlins since the roof was not going to extend to the fascia, but when we started putting the purlins up I made the mistake of putting them up in the two northern outer segments and upon reflection decided it was good and to leave them. This change though meant that we were 5 x 6m lengths of timber short.

I made the decision to leave the 3.6m and 2.4m lengths out of the last 5 segments (the ones either side of the ring beam). I did this because I should be able to fit those lengths onto the trusty old ute and pick them up myself, saving on delivery charges.

Due to the weather the timber mill has been unable to get extra bits of the Coastal Grey Box for the last few months, but today I got a call to say that it is in and ready to be milled (yippee!). Which means that we should have the timber within the next week.

Little by little

Our little building site has still been fairly quiet.  We managed to get a quarter of the purlins (the timber that will hold the roofing iron on and our ceiling up) up a little while ago, with the help of a friend Garryn. 

quarter of the purlins up (half of the long ones though!)

 The purlins are all different lengths for each segment of the decagon shape of the roof (confused yet??).  They are held up with a custom made bracket and 2 bolts into the pulin and 2 into the main beam.

View of the brackets and the attachment to the main beam

This timber is the smallest (and supposedly the lightest) of the timber we have used in the frame.  Still too heavy for manual lifting, so we have kept using our lifting device for these too.  Its been an invaluable tool on the building site, and made the whole process safe and fairly easy.

Brad, Garryn and the lifter in action!

Hopefully the next post on this blog will be a celebratory one to say that the framing stage is finished!  Then our building surveyor will inspect it and hopefully give it a big tick of approval, which will mean we can get started on the (white) roof, and then the luxury of undercover workspace!  

A little progress - the fascia boards

Its been a bit quiet on the building site lately.  Such is the life of an owner builder!  But some progress has been made.

We had brackets made up to put the purlins up.  140 brackets and they needed to be painted as well!!  We have purchased the bolts to attach the brackets and purlins to the main beams.

We spent a whole day cutting and putting up the fascia boards (literally a full day, as Brad finished up in the light of the full moon!  They went up fairly quickly with our trusty 'lifter' - the lifting device we built to handle the heavy timbers.

All that remains to finish the frame are the purlins (70 beams that go between the main beams).  This will probably be a pretty intensive job as there is a lot of timber to put up.  We hope to get stuck into that soon!

Then we will be gearing up to put the roof on which will make building life a whole lot easier!

The Design

Well, we've been talking mostly about building the Round Strawbale House so far, but since there hasn't been a lot of building happening lately I thought now would be a good opportunity to show the house design and talk a little about it (I hope to write detailed blog posts in the future about each of the design elements mentioned below).

As you can see from the plan that the house roof line from the top view is a regular decagon. The reason we chose this shape is that we wanted a round house but making an actual round house has it's difficulties, so we squared off the edges and chose the decagon because for the size house it gives a beam length of ~6 metres between the outer posts. Any timber above 6 metres starts to become exponentially more expensive and the bigger the span the bigger the timber cross section. There is a balance between the number of posts required and beam length.

An important design aspect of the house is the sunroom located on the north side of the house. This room covers two outer segments of the building. These two segments are different to the rest of the roof in that they only have roof cladding to just past the inner ring of posts (the overhang will be about 1.2m to shade the entrance in the hottest part of the year in January/Feburary for where we live in South Eastern Australia). This room opens into the living room, one of the bedrooms and the bathroom with the idea of using the sunroom in winter to passively heat the house. The sunroom can also be used to cool the house in summer by drawing air through the house from the south side which will have shade trees.

The next thing you will notice that all the outer walls are strawbale which have a wall thickness of 500mm, this provides a good thermal barrier to reduce heat loss in winter and heat gain in summer. The inner walls are mudbrick and will most likely be between 150mm-200mm, the idea of this is to provide internal thermal mass to keep the house internal temperature relatively stable. The outer walls are all quite curved and do not follow the roof line. This was done for aesthetics, to provide interesting nooks and crannies around the house and because I like to give myself a challenge in building. If you're going to build a round house, might as well make round rooms.


The living room and kitchen are combined into one big room (which is round) in the centre of the house. The idea of this is that the main room in the house is insulated from the outside by the other rooms except to the north which opens up into the sunroom. The kitchen will have a combustion stove that will have the capability to heat our hotwater service and to run a hydronic heating system required. If extra heating is needed then we will locate the radiators for the hydronic heating in the outer rooms. The kitchen shares a wall with the bathroom and is close to the toilet to reduce the plumbing required.

We spent a few days last week on putting up the fascia(6m x 300mm x 35mm) and are currently getting ready to put up the purlins (have got bolts, brackets and timber only need time).

Location, Location, Location!

Location is a very important part of building a house, and probably one of the most important when building a sustainable house  Its also one where some important factors are often ignored. It is one of the cheapest ways to improve your house efficiency since where you place it can have a big impact on heating/cooling. I am going to discuss location with regard to building on a piece of land that is already purchased.

The factors that dictate where you build will change depending on your latitude and local climate. Some common location factors here in Victoria that are usually taken into consideration when building a house are:

1. the view - important to some people, I personally don't mind taking the time to walk to a place on the property to admire the view (on a good day we can see Western Port Bay and Wilsons Promontory National Park), it makes it more special.
2. access to the road - it can be cost prohibitive to build a good long track, but the benefit's are privacy and less disturbance from local traffic.
3. distance to services, ie. telephone and electricity - this can have a major impact on the cost of connecting to public services, running power/telephone a long distance increases the cost of earth works and the cost per meter of cable for power, and could require 3-phase connection depending on load and length of cable. For us this wasn't even a factor since we had decided long ago to run of our own power (solar and wind) and are successfully using mobile broadband and voip for phone.

The major factors that WE used when choosing a location to build our house on the property were

1. has good sun access in the winter (when it is needed, our winters are quite mild with some snow every couple of years) - this is important for passive heating, you do not need to face the front of the house north, just have the big windows facing north (with adequate eaves to shade out direct summer sun).
2. protection from strong winds - this can be negated by planting trees and building shelter around the house, but why do that when you can do the same with less cost by good placement. The last thing you want is to be blown away as you step out of the house. The other thing with an exposed house is that the wind will cool it down, a sheltered spot will naturally have less heat loss.
3. use of natural environment - for us the site has a hill to the east which shelters us from the wind. The other side benefit of having the hill next to the house it that it will be the perfect place to put a water tank on top of to supply the house (by gravity, avoiding the need for electric pressure pumps).

There are other factors that you need to be aware of are the local council building regulation that dictate setbacks from boundaries, creeks etc. This is important to know when buying a property as a spot that you think would be ideal to build on can be excluded by these laws, which usually are very strictly enforced (some for good reason). For us, we are located in an erosion overlay in rural Victoria. We have a creek starting in the middle of the property which has a setback of 100m and a 20m setback from the boundary which severely limits the spotsp where a house can be placed. We picked out several possible house sites at the time of purchase based on setbacks and flat spots that would minimise earth works (and hopefully house footings).

After buying the land we then spent the next few years assessing the different house sites based on weather conditions at different times of the year, during the extremes, summer and winter and the change in autumn where we get strong westerly winds. We noticed that when we got the extreme winds that one of the sites was sheltered (a big plus to that particular site). We were not keen on building near the road as privacy was a consideration but one thing that we noticed was that passing traffic on the dirt road during summer causes a large dust cloud that would cover anything near the road in a thick layer of dust (a big minus for any site near the road).

The extra benefit of the sheltered site is that the hill that shelters the site is ideal to put the solar panels and a water tank on top for gravity fed water. This eliminated the need to run a water pump whenever water is need in the house. Water will be pumped up using an electric transfer pump running straight off the 12V DC battery bank.

The other thing to watch for when choosing a location to build your house are pockets of low land which can trap cold air and frost during winter, the stability of the land. We are building in an erosion overlay and the surrounding area has visible signs of land slippage. This can increase the cost of house footings considerably and the last thing you want is for your new house to be split in half by moving foundations.

My personal 'favorite' biggest house location mistakes are facing a house's main windows west (closely followed by south). Which means you have the hot afternoon sun shining directly in, and the only way to avoid the sun is to block it. Also building on top of a hill where you are exposed to the elements. If you do want a nice view then the choice of property is very important because it's very hard to enjoy the view when the sun is streaming in through your nice big windows on a 40°C day or you get blown away by the wind every time you step outside you house in autumn.

Other important topics of location are with regard to location of windows and rooms in the house which will be discussed some time in the future.

To finish off here is a picture of our house and a description of its location.

As seen from the hill next to the house site

This picture was taken in the morning. You can see from the shadow that west is to the top of the photo (you can see the road which is one of our boundaries), north is to the right, south is left and the photo was taken with me standing on top of the hill to the east of the house.

The 'front' of the house is to the north, where we will locate the sun room for passive solar heating in the winter. The west side has the bathroom, toilet and a short hallway(storage area). The bathroom will have west facing windows but we will have a treed outside area to shade the windows in hot summer evenings(we are may make this outside area accessible from the bathroom). The hallway will have a narrow long window facing south west for light and a view of the paddocks to the south and west (this window will most likely be one that is tinted and has high IR blocking).