Invented twenty years ago in Brittany, the Kerterre, a house of hemp and lime, can be counted today in the dozen in France. A habitat that is easy to build, inexpensive and respects the environment.
In the hamlet of Lanvénaël, at the tip of Finistère, it is difficult to find the Kerterre. These small round houses are hidden in the vegetation. Tall grasses, prominent bushes, fruit trees, dense forest … A Breton jungle conceals these dwellings which are reminiscent of the houses of Hobbits. Round, smooth and white, the Kerterre blends into the landscape, like a large rock. They have been developed and perfected by Evelyne Adam over the years: “The same Kerterre is 20 years old, presents the one who is at the origin of the ashes of formation. One day, someone gave me hemp, directly taken out of the field. I soaked the whole plant in lime mixed with sand [giving a kind of sticky vine] and I built a first igloo using this technique, like with plasticine, without the need for structure “. As it dries, the mixture of lime and sand turns hard and becomes stone again.
Evelyne Adam did not invent the alloy of hemp and lime, but she innovated by using the whole plant, not defibrated (read the box). This material makes it possible to sculpt houses without the need for framework: “I also tried to make a Kerterre in clay, remembers Evelyne Adam, but if it took water, without reinforcement, it would collapse. in hemp and lime is more solid. “
Strong and inexpensive
Indeed, the “granny” Kerterre has nothing to envy the youngest … No wrinkle cracks its smooth surface. Its skydome – the half-spherical pane that provides a skylight in the house – is always well hung. It is made of polycarbonate, a plastic little known for its ecological virtues, but which Evelyne Adam preferred to glass for its thermal qualities and durability. Particular attention is paid to the origin of the raw materials: hemp, sand and lime are French; windows and doors are made to measure by local craftsmen. It takes around € 2,500 for the complete structure (including walls and openings) of a Kerterre 5m in diameter.
In order to learn these construction techniques, trainees come to the training site several times a year: “We put the hemp fibers, soaked, on top of each other and we wring out the plant,” explains Fabienne. This intern, who came from Belgium, works to integrate a colored glass sphere into a wall. “The hemp fibers must intertwine and the air, useful for insulation, must not come out. In three weeks of practice, without needing a lot of material, we can make a small ecological house”, she rejoices, massaging the hemp until the mixture of sand and lime begins to solidify. The Kerterre is actually built by hand, no need for a concrete mixer or large tools. “I had the idea of creating an easy-to-make home for women, explains Évelyne Adam. It is always the men who built the houses. Thanks to Kerterre, women reclaim their home.”
Femininity is also part of the very essence of Kerterre or more particularly a concept that Evelyne Adam calls “Touslessens”: “A feminine principle that characterizes the capacity of women to see everything as a whole and to do several things. things at the same time. We have to assume that sometimes our mind is going all over the place. Men often think it is rubbish, because for them it is straightness that matters. that everything be straight, square, well measured, with plans … While the Kerterre is not 100% predictable, even if there is a part of rectitude in the fact that the doors and the windows are made tailored. “
Building with hemp fiber, a marginal technique
If Évelyne Adam uses the entire hemp plant, this is not the option used and recommended by the professionals of the Construire en hemp association “hemp fiber, like all plants, contains a lot of sugar, specifies Quentin Pichon, technical consultant of the association. This sugar disrupts the setting of lime. It is possible to use the Building with hemp fiber, a marginal technical fiber on walls of 5 to 10cm, but with a greater thickness, the inside of the wall risks not solidifying and remaining in the form of sand. ”Hence the use of chènevote, defibrated hemp. Its first use dates back to 1986, by the mason Charles Rasetti. After more than ten years of experimentation, the Construire en hemp association was created in 1998 to regulate these new construction techniques and approve pairs of binders and aggregates; if hemp is used to create hemp concrete, the types of lime differ depending on the intended use. Evelyne Adam, for example, uses hydraulic lime 3.5, suitable for exterior constructions or damp rooms. But the use of undefibred hemp is not part of the professional rules of hemp construction.
Sculpture or masonry?
Indeed, seeing the trainees apply to construction, we understand that it is more sculpture than masonry. The walls are intertwining of unprocessed hemp plants, glued together with lime. The rounded shape asserts itself because the slimy lianas can hardly form a right angle. A real elongated modeling clay that allows you to create curved walls. “The mixture of sand, lime and water also varies according to the air temperature and the advancement of the Kerterre, completes a trainer. The hemp wicks move, it is not brick.” The theory is verified as soon as the trainees install the base of the door: hemp concrete with gravel for the water flow, interspersed with slates to prevent humidity from rising on the walls. A technique used throughout the base of the Kerterre, but that must be enhanced at the level of the main opening. Men get annoyed that women don’t use a level, don’t necessarily want to measure. Trainers are used to these reactions. The construction of the Kerterre is certainly not millimeter, but so far, none of them has collapsed.
Round like the earth
The flexibility of hemp is also its strength when it comes to building in the round: “It is the most logical shape in terms of construction, believes Evelyne Adam. The round is more resistant because the forces are better distributed. “. Like the planet, the Kerterre wants to be round to be connected to the living. Ker, in Breton, means “house; Kerterre can therefore be translated as” house linked to the Earth “. On the ground, no concrete slab but a thick hemp mattress about twenty centimeters thick:” C ‘ It is important to be in direct connection with the energy of the earth, explains Évelyne Adam, especially at a time when humanity is living more and more above ground. ”In the evening, the inhabitants enjoy observing the stars through the skydome, listening to the sound of the fire cracking in the fireplace. A rainwater collection basin allows you to wash thanks to a phyto-purification system. The air circulates freely, through ventilation holes and windows let in abundant light. Trees and plants grow naturally in the house. “Living in La Kerterre allows you to discover other relationships with natural elements, says Evelyne Adam. I warm myself in the dead wood of my forest. I use the ashes to wash my clothes, and a lot of plants in my garden, like the cleavers which acts as a sponge. It is not sobriety, on the contrary; living in Kerterre for about seventeen years, I found an abundance of time and links with nature, while maintaining a certain modern comfort thanks to the electricity of the solar panel. I spend less time cleaning, but I continue to be able to watch films … Going towards nature is not going towards decline. On the contrary, it is walking towards abundance and living in Kerterre allows me to have a beneficial impact on the environment. “
But the Kerterre is still far from filling our housing estates because it is considered not as a dwelling but as a sculpture. It is therefore not possible to obtain a building permit for a Kerterre. The people who currently inhabit them benefit from the legal vacuum according to which it is not forbidden to inhabit a work of art. “I know that two people have obtained written agreements, signed by the municipalities to build Kerterre”, specifies Evelyne Adam, full of optimism and who continues to carry out actions to obtain the authorization of these constructions in the rules. The Kerterre of the future? She sees them as “beautiful, like minicathedrals, all sculpted. We would make Kerterre with several domes, Kerterre-cinema, Kerterre-sauna … Kerterre where we will enjoy everything that we have invented that is magnificent, but no longer connected to earth “.
Text by Marion Paquet