Week 5 – Cob camp hits the road to learn eco-building in the Pyrenees
Posted on 24 June 2011
The beginning of week 5 was all about mixing and building cob since the roof was up and stable. There is so much to learn about cob that you can only truly understand through tactile experience. You need to feel the critical proportion of clay to sand to ensure a plastic, cohesive, workable mix that won’t shrink and crack too much. Depending on the coarseness of the sand and quality of the clay (and other components in the soil) the final mix should be between 5% and 25% clay. By observing the soil composition from a soil test (seeing it settle in a jar with water) you can estimate proportions.
But, it is the snowball test and crunch test that helped us refine the mix. For the snowball test we created a sphere from our mix, held it 1m above soft ground and let it fall. If it shattered, it was too dry or sandy. If it flattened it had too much clay or water. Ideally it would hold its shape on impact. The crunch test is where we would squeeze some cob near our ear. If it had enough sand we would hear the sharp grating sound of sand grains rubbing against each other like sandpaper. The reason this is important is because we ultimately want to build a wall of sand grains mortared together with clay. The sand grains should be touching one another so that the mix can’t shrink much as it dries.
Visually we could also rectify the mix. If the mix was sticking to our feet or tarp we added more sand. If the mix was crumbling or not holding together, we would add clay and/or water. If we could pull the mix apart too easily we’d add more straw… and so on.
Whilst building, we would apply the cob, perforate the surface with a cobber’s sick (or our fingers) to marry the cob to the mass of the wall, help the next layer to bond, help the wall dry evenly and accelerate drying. It is important not to overwork the cob, pat it or slap it. This can cause it to slump or a smooth surface slows down evaporation preventing the inner parts from drying quickly. For parts that mushroomed out we sliced them off when they were drier. Whenever we started cobbing again we moistened the surface so it was damp and soft for optimum adhesion.
I felt satisfied with what I’d learnt at cob camp, but it was time for change. When D and Samantha got invited via the helpx website (helpx.com) to an eco-build project in the Pyrenees, it seemed like a perfect opportunity for Wayne and myself to tag along. So, on Wednesday I said goodbye to Jean who returned to Paris to study and D, Samantha, Wayne and myself squeezed ourselves and all our gear in to Wayne’s van for a 6 hour drive south.
Arriving in the Pyrenees
We immediately felt inspired and motivated on entering this beautiful region and meeting Anne and Pierre. This Anglo-French couple met on travels in India in the 80s which definitely shaped their thinking and rich, modest lifestyle. Pierre mostly lives on-site at the moment where they are building their house and barn. Since Pierre is doing the building all by hand and by himself while Anne home school’s their children, they welcome people interested in eco-building to help in exchange for experience, food and accommodation.
To introduce you to the area, here are some photos from my early morning walks around the nearby town…
… the nearby grape vineyards and fields of wheat… alongside are fruit laden, largely unharvested corridors of cherries, walnuts, almonds, plums, figs and more… and the gardens contain a mouth watering assortment of fruit and vegetables! One of the couples on site eats around 60% of their food straight from their garden.
…and the site itself, with its garden allotments, our outdoor kitchen and bender (a communal cooking/eating/hanging out space Pierre made from bending branches in to a frame)…
Our first day was spent getting oriented, chatting and receiving our first lesson before attending an exhibition where Pierre’s art was being displayed. Already a rewarding day!
Natural Roof Insulation
Our first lesson was how to insulate the barn ceiling with local raw sheep wool. Pierre explained that this unprocessed wool sold for 10cents/kg 2 years ago but is now more like 1Euro/kg because of the rise in popularity of eco-building (who mostly don’t use it raw). Since the barn needs 450kg of it, Pierre has developed relationships with locals to get it for a good bottle of wine J. A book I have been reading, ‘The hand-sculpted house’ by Ianto Evans, Michael G. Smith and Linda Smiley, confirms this availability of wool: In New Zealand insulating with bats of woollen insulation is standard practice. Elsewhere, the world’s wool market has been sluggish for around a decade, so in places like the U.S. and France it can be obtained quite cheaply directly from the farmer. Sometimes low quality fleeces will even be donated by farmers interested in the project.
Pierre explained that wool is also a good insulating material because it can hold 33% of its own weight in water and when it dries out it doesn’t lose any of its insulation property, unlike other materials. ‘The hand-sculpted house’ informed me that sheep’s wool has a thermal resistance slightly better than fibreglass, it continues to insulate when wet, is relatively flame resistant and of course, natural, lightweight and non-toxic!
Pierre also showed us how to install the timber, then a layer of cardboard (to prevent dust falling through), then the wool sprinkled with lavender or cedar chips to repel moths. According to the aforementioned book, leaving the lanolin on the wool also protects it against moths (so make sure you don’t wash it with soap!). If you wash and card (tease and fluff up) 2kg of wool, you can make 0.03 m³ to 0.08 m³ of insulation. However, this is an arduous process and using the whole fleeces in the condition they come off the sheep (as we are doing here) is much easier. Apparently some people put the fleeces in plastic garbage bags to layer in the ceiling and this has the added benefits of containing odours, discouraging moths and is a built in vapour barrier. The method of moveable timber panels also means easy ceiling access if needed later. These photographs show the panels we put the wool behind (sometimes we had to trim them to fit them too):
From what I have read, the amount of insulation depends on your climate so you could actually check your local building codes to use as a guide. Above the insulation, it is recommended to have at least 5cm of uninterrupted vent space so that air convection can continuously take away any condensation from the space between the insulation and the roof covering. The vent will also help keep temperatures down when the sun is high.
The barn where we were doing the insulation is a mixture of rammed tyres as pillars, earth bags at the base and straw bales to the ceiling covered in a cow dung, straw, mud mixture. To date, Pierre has used 213 straw bales for the barn walls and mixing in the plaster.
As for the house, it has had its foundations built from 700 car tyres rammed with 70m3 of gravel. On top of these are layers of earth bags with barbed wire between each layer. Pierre has used over 1000 earth bags on the house. The flooring of the house consists of a geotechnical steel membrane followed by gravel and earth and left to naturally compact by the weather. These layers amount to a thickness of 30cm which once naturally compacted should be more like 20-25cm. This depth is required to protect against moisture as capillary action from below can occur up to approximately 6cm whilst condensation from above can seep down to around 5cm.
On Friday Pierre taught us how to set up the 6m teepee he made around 4 years ago. As someone who loves art, architecture and prefers to use tensions rather than cutting and reconnecting materials, I can see why this structure is so appealing to him. But what’s even more impressive than his natural, methodical elegance in constructing this huge, heavy structure (with our help this time) is that he made it all himself! He cut down the 7m timber for the poles; carried them down the mountain and shaped them; he designed and sewed the canvas and internal layer; he made the cow dung base for it to sit on. Every aspect of the teepee has Pierre’s attention to detail in it and I was thrilled to listen to his detailed explanations and knowledge!
Activity rather than work
The remainder of the week was spent undertaking ceiling insulation and attending the occasional event such as an evening with a Jazz singer at the site as part of a festival, eating lunch with the other members of the community and visiting a nearby market. Personally, I also continued meditating and growing my awareness and state of presence. This was greatly helped by Pierre’s approach where he views himself as doing ACTIVITY rather than WORK. Activity relates to the condition in which things are happening or being done whereas work is the mental or physical effort done in order to achieve a purpose or result, often as a means of earning income, a job, or a task a person has to do for some reason. I enjoy this concept as it means you can naturally achieve what needs to be done, whilst respecting your own limits, body and emotions.
I’m enjoying the changes this week has brought – change of scenery, project, building techniques and pace – so I’m also looking forward to what next week will bring.