Earth building is cheaper than conventional building – but only if you do it yourself, says Sam Southward. He built four light-earth constructions at the delightfully named Absurdistan Community near Kaiwaka. Sam was happy to chat and share what it takes to build in light-earth.
Sam (74) and his partner, Prasado Straub, have lived at Absurdistan as founding members since 2001. The community is made up of thirteen like-minded friends who shared ideals and were keen on the idea of living in a community. The name Absurdistan is a light-hearted riff on the ‘stan’ countries of Central Asia, says Sam – a reminder not to take themselves too seriously.
In 2001 they purchased 40 acres on a headland jutting into the Otamatea River, a particularly beautiful part of the Kaipara Harbour. All members contribute to the well-being of the community. Together, they gather food from the communal gardens, which provide the main community occupation for green-fingered Prasado, and prepare and share evening meals in the communal kitchen and dining room.
The communal hall
The group agreed they would be better connected with one another if they first constructed a communal building. It fell to Sam, as an experienced licensed builder, to design and construct the hall, affectionately referred to as the Buddha Hall. It took two years and approximately $200,000 to build.
The result is a spacious 120-square-metre octagonal building with a skylight at its apex. The building is ‘chemical free’ – made entirely of natural materials.
Light earth with pumice
Light earth is made of clay and other natural components, most commonly straw. However Bean had been using pumice, because breaking up straw with pitchforks and coating it well with clay was too slow and labour intensive to be commercially efficient. He mixed clay and water in a second-hand baker’s dough mixer until it was milkshake consistency, then added ground pumice from the Bay of Plenty.
Because he was finding it increasingly difficult to earn a living from light-earth construction, Bean sold the dough-mixer to Sam.
The walls of the communal hall are an 80% pumice and 20% clay light-earth mix, packed by hand between sheets of ply placed on either side of the double framing. They were left for a couple of days to dry before the ply was shifted along to the next section.
The exterior was sealed with sand and lime plaster, then finished with a coat of lime-wash. “I experimented with a homemade mix of lime and casein on the interior,” Sam said, “but it kept ‘dusting’, so we painted it with Golden Fields’ BioPin wall paint (natural paint)”.
Double framing and roof beams for the hall were constructed from Lawson’s cypress, and cut by St Lukes Timber to the unusual dimensions required (300 x 100 mm and 7.5 metres long). Each roof support beam is bolted to a steel I-beam around the peak and, to keep them from splaying at the bottom, a steel cable runs through each beam where it meets the wall, around the circumference of the octagon. All the joinery is made from macrocarpa.
The hall has a 600 mm soffit, but today a minimum two-metre overhang would be required – essentially a verandah. The Earth Building Code (NZS 4298) requires a 1:1 ratio of wall height to overhang, to protect the walls from the weather.
“The south-facing wall gets strong wind and rain,” said Sam, “so we painted it with Keim paint which repels water and is weatherproof. After a few years some of the final plaster coat washed away on this wall due to insufficient initial wetting. Walls need to be sufficiently wet that plaster properly adheres, otherwise it sucks the moisture out and ruins the bond.”
Fixable with the materials it was made from, the wall was repaired and finished with two coats of lime-wash, and has been perfect ever since. Sam says if the weather is extreme on any wall it’s probably wise to add a cladding over battens.
Light-earth homes with straw
Once the hall was complete, Sam built an 80-square-metre footprint home for his next-door neighbour. She decided on light earth, but Sam didn’t use pumice this time, because when the mix achieved the correct dough-like consistency, it became extraordinarily heavy and difficult to extract from the mixer, requiring a really strong person to empty the machine.
He chose instead to use barley straw with the clay, and sourced some from a Dairy Flat stock feed company. It proved easier and more pleasant to work with than the pumice. Barley straw is a recommended medium; it’s softer and less brittle than wheat straw and therefore stronger. It is also more brightly coloured and far less prone to rot.
“You need as much straw as if you were building a straw-bale house,” he says. “So you work out how many bales you need for wall height and the area you want to encompass and that’s the correct amount for a build.”
Mixing up milkshake and salad
Clay on the property proved unsuitable so it was trucked in at $200 a load from a Mangawhai quarry.
Two people broke the straw up then poured the milkshake-consistency clay slurry over the top of it onto a sheet of ply. Two others tossed it like salad with pitchforks until the straw was completely coated. The mix was then packed into the 300 ml gap between the double framing, with ply cladding either side to hold the mixture in.
After the first load of well-coated straw had been tightly packed, the ply was removed within an hour (much quicker than the two days for the pumice–clay mix) and shifted higher up to continue packing until full wall height was achieved. Careful and determined stuffing at the top is needed, because the top plate is already in place, and the gap into which material can be pushed becomes smaller and smaller until it is non-existent.
There’s no need to be precious with the consistency of the mix, says Sam. Once they got down to the job it was obvious how much moisture content was optimal. “You could feel it in the way it held together as you packed it.”
It’s important that every piece of straw is coated with clay to avoid the potential for it to compost within the walls. Clay absorbs and releases water, ensuring stable humidity in a light-earth house built with straw. Because cement retains water, it should never be mixed with clay.
To stabilise the earth in-fill within the studs even further, Sam laid lengths of bamboo horizontally every 600 mm up the wall.
He used the same light-earth system in his own house. The walls are only 150 mm thick – which he says works because the house is relatively small and easy to heat. Sam’s house and his neighbour’s house both have an 80-square-metre footprint with a 40-sqare-metre mezzanine level.
The requirement for earth buildings to have a 1:1 ratio of wall height to overhang makes it difficult to build a second storey with light-earth walls, so the upper level of most two-storey earth buildings is made of timber.
All the woodwork in Sam’s home is Lawson’s cypress or New Zealand-grown cedar, and the floors are eucalyptus in all four light-earth buildings he has built at Absurdistan.
Sam also built a two-storey 200-square-metre home for another neighbour, Hermann, using mainly light earth on the lower floor. This house has weatherproof timber cladding on exposed exterior walls where there is no soffit. Both the neighbours’ houses are roofed with clay tiles, which are durable, although they’ve attracted mould and need cleaning to maintain their look. Sam and Prasado’s house is roofed with recycled tiles from the old Kerikeri Post Office.
Hermann’s house has a Biolytix flush toilet system, which incorporates a tank with worms and filters and, when filled to a certain point, pumps through irrigation hoses into the bush. The nextdoor neighbour opted for a Natural Flow toilet system, which separates the grey water from the black, and worms are also used to process the sewage.
Sam has chosen a dry composting wheelie bin system. Four bins serve this two-person household for a year, after which nothing is left but rich compost, which Prasado feeds to fruit trees in the communal orchards. Their grey water is released through a grease trap and flows downhill to feed their banana trees.
The other two homes have solar water heating systems, but Sam and Prasado have an old Rayburn stove which heats the water, provides a cooking facility, and keeps their home warm.
If he had to build his own place again, Sam would increase the wall thickness to 300 mm. Hermann’s north-facing house with 300-mm-thick walls barely needs heating, although it does also incorporate large windows that allow the sun to reach an internal light-earth wall, which acts as a heat sink.
All three houses are finished in natural plasters, which absorb and release moisture as do the walls themselves.
These naturally breathing light-earth homes are cosy and well insulated, creating a sense of sanctuary for Sam, Prasado and their neighbours in this idyllic spot.
- Location: Parekura Road, Kaiwaka
- Five light-earth buildings: community hall and four residences
- Other buildings: three houses, community kitchen and dining building, public composting toilet, various small outbuildings and sheds
Need light-earth information?
Sam likes to help others with building projects, in particular earth-building projects to which he can contribute his considerable experience and information that he’s accumulated over the years.
Contact Sam Southward: [email protected]
© Copyright Theresa Sjoquist 2021
First Published in Organic NZ Magazine – November/December 2021 – Vol. 80 No.6