Friday, 28 October 2011

Becoming an Owner Builder

When lodging the DA Council want to know either the builders name or if you are an owner builder and ask for the licence number, but to apply through Fair Trading for an owner builder licence the form wants to know your DA number.

Fortunately back in May 2011 while I was still working through the design options I completed my Occupational Health and Safety White Card, a one day course through The Training Course Professionals. This was a prerequisite for completing the Owner Builder Course which is a requirement in NSW to get an Owner Builder licence. I completed my Owner Builder Course on line through Abacus Training. Once you pay the $197 you just download all the reading material, including a surprisingly helpful study guide that summarises many of the important parts, do your exams on line and then get your certificate e-mailed.

Having collected up all the required pieces of paper I applied at the Department of Fair Trading on Monday and my owner builder permit arrived in the post on Thursday.

Plans to Council

Once hemp masonry became my first choice of wall material I contacted Shoalhaven Council to find out what information they needed. On the basis that the hemp masonry was non structural and the timber frame met the NSW Timber Framing Code the Council officers did not seem too concerned about my wall choice. None the less when I lodged my plans I included copies of the technical drawings and technical information parts from both “Build a House of Hemp” and “Hemp Lime Construction”. It has been almost two weeks since I lodged my plans and checking on the electronic DA tracking my DA seems to be progressing normally.

I applied for my DA and Construction Certificate in the one application. As I had nominated Council to be me certifier I paid for my Occupation Certificate at the same time as my application, the application fee at $1,800 was higher than expected. Plus I still had to make my contribution toward the Long Service Levy, although I was applying for a partial exemption.

 As I was at my block supervising the removal of some trees I lodged my DA at Council in person, something that had been recommended in my owner builder course, so as not to delay things if your documentation. This was a good choice as, although my documents were all in order, I was required to fill in an extra Jervis Bay Environmental Plan form that referred to a number of maps, located on the wall adjacent to the lodgement counter, but not available on the internet or elsewhere.

In addition I paid my $110 and picked up my beautiful blue wooden peg to put in the ground where I wanted my water metre to go in.

Unfortunately, I had to have three trees removed to get the electricity on. But the boys from CT Tree Services arrived at 8am with a 60ft cherry picker, and after a period of assessment moved into a smooth deconstruction of the trees branch by branch. By the end of the day the trees were gone and by lunch the following day so were the stumps.

Billen Cliffs House

After the weekend workshop we had the opportunity to visit Graeme and Patricia’s hemp house at Billen Cliffs, see their home and talk to them about their hemp building experience. Graeme and Patricia truly were pioneers. Over the build they used hemp fibre from three different crops. At the beginning of the build some of the hemp fibre was different lengths, but they found shorter was better and this was what they continued to use later. Some earlier patches also showed a little bit of ‘balling’ in the mix. Patricia emphasised, as Klara had, the importance of getting the right mix and to monitor the quality of each mix. They also pointed out that using wet or dry sand would alter the moistness of the mix.

These lessons were clearly learnt as the second storey was much more consistent. The hemp masonry for the second storey of their house, consisting of an open plan kitchen, a bathroom and a bedroom, was done in 6 days with a crew of 6 to 8 people, this involved about 4 days of mixing and pouring and 2 days of formwork. It was good to see how they had put the water pipes and conduit and boxes in for electricity before the hemp masonry was poured, avoiding the need to chase it in later.

On the lower section they had exposed the timber studs on both sides, making a feature of them, however there were some gaps under the noggings. With the second storey they discovered that covering the studs, at least on one side, was more successful and solved the problem of gaps and shrinkage. It was good to see the firm well done walls.

Their resourcefulness was shown in their cut down 10 litre plastic containers to make just the right sized scoop for putting the hemp in the forms. Their willingness to experiment has continued with their hemp walled composting toilet. They also tried a number of different render colours and making patterns of the render.

Many thanks to Patricia and Graeme for allowing us to visit and photograph their house, for sharing their experiences and for the tasty pumpkin they gave us.

Wednesday, 26 October 2011

Hemp Workshop

Plans were drawn and ready for Council, but first I had to make sure that Hemp Lime Masonry construction was manageable, affordable and aesthetically pleasing. My opportunity to do this came with a workshop conducted by Klara Marosszeky, from the Australian Hemp Masonry Company, held at Mountain Top 45 mins north of Lismore in early October 2011. 

The workshop took place at Auntie Liz Johnson’s property where workshop participants had the opportunity to build the floor and walls of the post and beam Aboriginal Cultural Field Study Centre. The setting was beautiful we were surrounded by tall trees, birds, goannas, and wallabies as well as ticks and leeches. The workshop participants came from Sydney to Brisbane and points in between, from farmers to professionals, all with a common interest in the use of hemp as a building material. Some were keen to grow hemp and others to build and the weekend was a great opportunity to forge links between producers and consumers of hemp fibre.

When we first saw a sample of the hemp masonry many were surprised at how hard the material had set. The hemp fibres were completely in the lime based binder but air gaps were evident that would contribute to the materials insulating properties. Klara showed the group the hemp stalks and various processed fibres. The hemp fibre used for building was more the texture of playground mulch, than what you think of when you hear the word fibre. 

The floor of the Aboriginal Cultural Centre was also to be made of hemp masonry. Prior to the workshop drainage had been installed under the floor and a layer of crushed rock placed between the concrete strip footings. The pole framing of the building and roof rafters were also in place.

Once we placed the geotextile layer, and after putting on our safety masks and gloves, lime is not good for the lungs or skin, the group launched into mixing batches of hemp masonry, pouring and tamping it in place, under Klara’s instruction. We mixed the material in a loud diesel pan mixer, it mixed large loads at a time but it was disappointing to learn that such mixers are not readily available in Australia – Klara’s being the only one for hire and specifically modified for hemp building. The hemp and binder had been conveniently bagged into batch sizes, so the mix was made up of one bag of hemp fibre, water, one bag of lime based binder, and sand. 

Klara reinforced the need to get the mix “just right”, which was the texture of damp muesli. When the binder was first added the mix looked too dry, but when mixed it combined surprisingly well. Throughout the weekend there were lots of comparisons of hemp building  to cooking and food preparation and by the end of the weekend workshop participants could tell if a mix was too wet or dry - having made lots of mixes over the weekend. We also learnt to watch out for “balling”, when the binder clings to the sand rather than the hemp fibre and forms hard balls. 

After mixing the other job was to tamp the hemp down, using specially made tampers - a handle on a block of wood. Unlike rammed earth just a light tamping was needed and the mix was slightly springy preventing it from being jarring on your arms.

At the end of a day of floor placing the sky opened up and the rain poured down as tarps were tied down to keep our hard work dry. After dinner, cooked on the fire, the group chatted about the days experienced and Klara spoke to the group about growing hemp, answering all the diverse questions the group put to her. We then retired to our tents for a night on the Mountain Top.

A warm sunny morning full of birdsong, a hearty breakfast and it was off to work again - this time starting on the walls. The building was a natural pole frame house and the walls were to be 300mm thick to take account of the varying thickness of the poles. Klara also tried a new method of formwork using threaded rod to join the formwork together. This took a little bit of tinkering to get right, but once the first section of formwork was in place the team got mixing.

The hemp was bucketed into the formwork and spread out to form 5 cm layers. Each layer was then tamped, using both large and small tampers. The small tampers were used first to tamp the edges and around any protrusions like the posts or a stud, then the larger tampers, that had been specifically designed to fit just inside the width of the wall, were used to tamp across the whole width of the wall.


I had a good, but tiring, weekend and definitely learnt a lot, including the hard to describe “just right” texture of a good mix. The weekend also helped me confirm that I would make my house out of hemp. The only disappointment was that the formwork would have to stay on until the following day and we could not see the product of our hard work. This was overcome with some promptly e-mailed photos. Tara Jones is making a film about hemp farming at Ashford and has further photos of the workshop on her blog

Many thanks for Klara for the weekend, to Auntie Liz for hosting us on her property and to the cooks for feeding the hungry builders and keeping the fire going.

Saturday, 22 October 2011

Materials Choice

In February 2011 I saw an article in Owner Builder Magazine about hemp construction, but dismissed it as too new and untested. At that time I wanted an exposed post and beam timber frame and was looking at natural infill materials. I researched Light Straw Clay, but had concerns about the straw rotting before the walls dried and the time required for the walls to dry. Hemp lime masonry and light stray clay use different materials but in a similar way, combining a fibre together with a binding substance.

I began to research hemp lime masonry construction and found that while it is relatively new in Australia it has been used in the UK for over 10 years and in France for 20 years. First stop I read “Build a House of Hemp”. I found UK book “Hemp Lime Construction” by Rachel Bevan and Tom Woolley a great resource, scientifically looking at the pros and cons and data in relation to hemp lime building. Also useful was an early study in the UK on the Haverhill Project done by the Suffolk building society, comparing the construction and performance of a hemp masonry building as compared to standard UK masonry construction.  "The Green Self Build Book" a UK book by Jon Broome also has a section on the hemp masonry renovation and extension carried out by architect Ralph Carpenter.

If I was going to build with hemp masonry the exposed timber frame had to go, and this was probably good from a maintenance point of view. One of the benefits of hemp lime construction is that it completely covers the timber frame protecting it from termites and rot, the hemp lime being termite proof and the lime and breathability of the walls assisting in the rot resistance.

Weighing up all the factors hemp lime masonry came up as my first choice for walling, it combines insulating and thermal mass properties, it reduces gaps by being poured monolithically in place, reduces the double handling of mud bricks, it is lighter and would be easier to work with than mudbrick or rammed earth, the lime sets as it mineralises avoiding the problems of clay rewetting, it has a comparatively low embodied energy and primarily uses natural materials.

Friday, 21 October 2011

The Design

From the time we made the first offer on the block we started thinking of designs, but did not want to get too attached until the block was ours, in case things did not work out.   We had previously been to Japan and I was strongly influenced by their architecture. I read numerous books on Japanese house design, both modern and traditional. I did not want to build a mock Japanese house but was more influenced by their concepts and philosophies behind their buildings. Their love of asymmetry influenced me add some breaks from the symmetrical. I was also influenced by their appreciation and expression of the natural characteristics of materials and appreciating the changes that occur as they age.  The traditional Japanese approach of designing the garden at the same time as the house and the consideration of the view from each window and part of the house, led me to the conceptualise several small gardens and courtyards only visible from certain rooms, as well as being able to look back at the house from inside the house.

I had also read Christopher Alexander’s “A Pattern Language” and “A Timeless Way of Building “ two years prior and kept many of the concepts in the back of my mind rather than directly referring to the books. We did not want an extravagant house, but had to keep in mind the dreaded “resale value” in case we needed to sell and recoup our money. I read Sarah Susanka’s the “The Not so Big House” and several other similar books from our local library. I also borrowed every book on ecological design, house building and the like that the library had. I wanted to keep the footprint to 100m2 but ended up at 120m2. The three bedrooms are called bedrooms but were deliberately sized so that they could be used as family rooms, tv rooms, play rooms, studios, studies etc, and even to allow these functions as well as providing for sleeping,  to allow for flexibility in the house as our needs change without the need for useless or rarely used rooms.

The pavilion concept slowly developed over many sketch drawings. It allows for good solar access and natural ventilation however, it does however mean that there are lots of external walls and lots of windows. It also shows the influence of Japanese design on the building. I wanted the design to be passive solar and referred back to my 10 year old copy of Nick Hollo’s “Warm House, Cool House” which I still find relevant and probably one of the most accessible and easy to understand books on passive solar design (I understand there is a new edition out soon). I even read the “Sunlight and shade in NSW” which was perhaps more technical than I needed, but fascinating for those who really want to understand the position and movement of the sun.

A Permaculture Design Course I had done previously meant that I was keenly aware of observing my site; the path of the sun at different times of the year and the differing shadows cast and the direction of the winds to both invite and exclude. 

And so the design evolved through many sketches, from two storeys to one, to prevent overlooking, angled to the block to catch the northern light and not have windows looking directly into neighbours yards. It developed further with helpful input over dinner from Ken, who is studying Architectural Technology, moving closer the the finished design and after many months of work in a form ready to obtain preliminary quotes.

Thursday, 20 October 2011

Buying the block

In January 2011, Ben and I, purchased a suburban block of land at Culburra Beach a 15 minute walk from the beach. We had long held the desire to design and build a house and had been looking for suitable blocks of land, then at the end of summer 2010 realised we had been looking in the wrong places and decided to look for something close to the beach.

We looked at maps and took exploratory trips down the NSW south coast. By winter 2010 we had decided that Culburra Beach was out first choice. It was about three hours from Sydney, had two beaches, a calm beach good for swimming as well as a surf beach, as well as a lake and a river. It also had some shops and good services, including an ambulance station, but we hope we will never need it.

Culburra Beach is a coastal town with housing of various ages and condition but little vacant land, particularly within our budget. We looked at doing a knock-down rebuild on a little old fibro shack, but this had double costs – you paid for a building you did not want then had to pay to remove it. Instead, we managed to find a battle axe block that was within our budget. The actual purchase took quite some time from the initial offer, but we were able to keep saving in the meantime.