Strawbale Building: The Home That Hugs You

kitchen
The kitchen features red cedar slab bench tops. Photo by Robyn Rosenfeldt

Shamus O’Reilly believes that strawbale is the best natural building material of them all. He recently finished building his own strawbale home for himself and his family. He also builds strawbale homes for other people through his construction company, SO’R Construction. He has repeatedly seen firsthand the benefits of building with strawbale alongside passive solar design.

Shamus and Jayde and their two young children recently moved into their strawbale home, located on a rural two-acre block in Inverleigh, Victoria. It was important to the couple to bring up their children in an environment free from chemicals and pollutants. So every material used in the build was selected for performance and low toxicity, and is renewable or recyclable. They love that every time they walk into their new home, it feels like they’re getting a great big hug.

‘My brother first pointed out strawbale as a building material. I did my building apprenticeship in Melbourne on high-end Toorak homes, but that was a lot different from how I grew up. We were the family that recycled. Mum and dad were into sustainability. Not that we called it that then. I grew up learning about how to select quality materials that were natural and re-usable,’ says Shamus.

‘Working for myself, I was conscious of waste. The more I worked, the less I liked working with chemicals and toxic materials. My evolution to natural building materials was through wanting to build energy-efficient homes. I still build conventional homes, but I am conscious of sustainability. My focus was on passive solar design of homes. Then strawbale came along and it aligned with my ethics.’

The Natural Feel

‘I like natural finishes. In a strawbale home, there are rounded corners and soft edges. It feels like a natural place to be and a welcoming space. I am a huge fan of rolled window reveals and wide windowsills too. In our home we decided to have a pine-lined ceiling. No paints, no thinners, not even natural oils – just timber. It allows the timbers to be what they are.’

Reducing Electricity Use

‘We have a wood fire in our home, but it’s just a supplementary heat source; it’s not really necessary. When the fire gets lit, it’s because you want to cook a roast, or for the ambience. With a well-insulated, well-designed home you don’t need to spend money heating or cooling it. The home will hold stable temperature for days. If you have cloudy weather for a week, you might need to light a fire. But a strawbale home is not a push-button home. There is no ducted heating, no turn-on heating and cooling. On a really hot day you might put the ceiling fans on.’

Straw Insulation

‘I believe that cob, mudbrick and other heavy mass homes, although natural and beautiful, have their downside. They will stay cool for two-to-three hot days, then they heat up and stay hot for a week. Once these homes are hot, they stay hot. That’s not the case with strawbale. Straw is an insulator; it stops the heat transfer. Our strawbale homes use cob, mudbricks or recycled red bricks on the inside as thermal mass,’ says Shamus.

Clockwise from above left: Baby Franky, Jayde, Shamus and Olive enjoying their new home; Shamus at his kicthen bench; The bathroom; Rounded wall entrance way. Photos by Robyn Rosenfeldt

Passive Solar Design

Passive solar design principles are an important part of all the sustainable homes he builds. The concept is to let the sun in during winter to heat the house, and hold the heat in with thermal mass. In his house the thermal mass is in the concrete floor and the brick wall that runs through the middle of the house.

In summer the heat is kept out to keep the house cool. ‘We design shade on the north side of the house and we plant deciduous vines – grapes or kiwifruit. So you have passive shade in summer and, in winter when the leaves drop, you will have full sun from the north. This works well with the high insulation value of strawbale and the renders on the inside of the house for thermal mass.’

Time And Cost

Building a strawbale home takes about the same length of time as a conventional build of the same size, so generally 9–12 months. However, Shamus has found most owner-builders he has worked with will take four-to-six years to build their strawbale home.

As far as cost goes, Shamus has found it is usually about 10 percent more expensive to build a strawbale home compared to a conventional home. ‘The extra costs are labour costs. The render makes it quite a labour-intensive way to build, with three coats inside and out for a 35mm thick render. You can try to employ free labour by running a workshop, where people come in to help install the strawbales and render and learn as they go.

‘For my own house, we didn’t have an open workshop as such, but we did have a few days where we invited family and friends to join us to install the bales and do the render. We had uncles and cousins and other extended family come along and help out. It’s something that people of all skill levels can do. We even had a 12-year-old family member join us; she worked for half a day and really enjoyed it.’

Site Selection

‘We purchased our block knowing that we would be building in strawbale. We chose it because it had a north facing orientation and it wasn’t going to be shaded by big trees. Plus the backyard was north facing. Also it was fairly flat so we didn’t have any large site costs, such as building retaining walls.

‘Most sites are suitable for strawbale building. Orientation to the north is important and a north-facing slope is ideal to achieve a good passive solar design. If you’re on a smaller site or subdivision, a north-facing rear yard or long block running east-west is great. It’s about having more of the home facing north.’

Design

‘Our home has a footprint of 20 m by 10 m. It’s an easy, rectangular shape that works for bale size and economical wall lengths. All the window sizes work to the heights and widths of the bales – this makes installation easier, as we didn’t have to do any cutting of bales.

‘The strawbales are like big Lego blocks. Sometimes people want a specific height in some rooms, but once you start chopping the bales your labour costs will go up. You don’t necessarily need to use an architect or draftsman, although employing someone that has experience working with strawbale does make the building process a lot smoother.’

Shamus has found getting approval to build a strawbale home with council is not a problem. Building with straw does require some specific engineering and additional documentation – check with your local council officers.

Foundation

‘We used a concrete slab for our foundation which provides thermal mass and is also quite economical. Our floors are concrete, finished with linseed oil and turpentine. There is really no limit on the foundation. You can use a concrete slab, a stem wall with footings and an earthen floor, or whatever you would normally use when building in conventional materials.’

Sourcing Bales

‘Our bales were sourced very locally – the farmer who cut our bales lives 10 minutes down the road. Being so close, we could go and look at the crop before harvest, then look at the bales again before we bought them. We also have a business relationship with this farmer and we source bales for our strawbale builds from him.

‘Most types of strawbale can be used, but generally wheat or rice is preferred. The most important thing is low moisture content and tightly packed bales with little or no seed head. The average home uses 250–300 bales of the conventional size of 900 mm long by 450 mm high by 360 mm deep. Depending on the season, each bale costs around $7.

‘It’s best to get bales straight from the paddock and into the build, so aiming for around December or January is best. Ordering bales early is also a good idea. If you’re a first-time builder, I would recommend using a strawbale supplier. You might end up paying $10 per bale instead of $7, but in the end that’s not a lot of extra money to be sure you’re getting what you need.’

house
The north-facing side of the house allowing for passive solar heating. Photo by Robyn Rosenfeldt

Framing And Strawbale Installation

There are two main systems for framing and installing the strawbales:

  • Load-bearing – The foundation is laid, the strawbales are stacked and the roof is assembled on top of the strawbales, which take the load of the timber roof. ‘Using this system, you need to get the timing right for delivery and installation of the bales, which can be a real challenge with our climate,’ says Shamus.
  • In-fill system (post-and-beam) – First build a loadbearing timber frame, get the roof on, then fill in the walls with the strawbales. ‘SO’R Construction has our own, modified, in-fill construction method that we use and recommend on all our strawbale builds,’ Shamus says.

‘We used an in-fill system in our home. We had the framing and roof up for nine months before we managed to get the bales installed. Once we got the roof on, our house was protected from the elements and we could wait till we had the free time to get the bales in.

‘Without the roof on, we had nowhere to store the bales and we would have been watching our home deteriorating in front of us. I’ve seen it before with owner-builders – if they use the load-bearing method and the weather comes in, or they have no good weather to get the bales in, it can go wrong.

‘For our house, we used all pine framing and tried to reduce any manufactured beams or treated timber. As much as possible we avoided any unnecessary glues and toxins during the building process.’

Render

‘The outside of our house is rendered using lime and sand and internally, we used clay and sand. Most of the walls were made with site clay – clay that we dug up from our building site. For the final coat we purchased bagged white clay, so the final coat was finished and we didn’t need to paint it. So there were no paints nor finishes used internally or externally; the wall surfaces are all rendered.

‘In Victoria there is abundant clay. Just about every building site we work on has beautiful clay for the render. Or there is usually someone close-by who you can get clay from. Someone might be digging a pool nearby. Or you could go to a quarry. It’s usually relatively cheap to buy; maybe the cost of a carton of beer.’

Insulation Options

‘The non-strawbale walls and the ceiling are insulated with Earthwool. It’s fibreglass but has no formaldehyde and uses a large percentage of recycled material; so it’s better than standard fibreglass insulation. Some people use natural recycled wool which is a composite product that’s made up of 90% recycled wool carpet offcuts and 10% polyester – the stuff that holds it together. There is no formaldehyde and no toxins. It’s naturally fire resistant. It’s just twice the price, so for our build we couldn’t justify the cost of the wool insulation and chose Earthwool.

‘We used timber-framed double-glazed windows and we super-insulated the ceiling. A normal home made of weatherboard will have external walls of R2 rating. Strawbale walls are R8. So it’s four times as insulated as conventional materials.

So that hug the house gives you when you walk in – the warming or cooling embrace – is more than just a feeling. It’s real and it’s measurable.’

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