Kerterre (small hand-sculpted hemp-lime building)

Passive · New build only

One of 10 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.

What your site needs

The lime, hemp and sand are brought in, so little depends on the site's own soil; what matters is a build season that ends at least two months before the first frost, and heating and ventilation through the first one to two years while the walls dry.

A small round building sculpted by hand from hemp strands soaked in lime, built up on a stone foundation into a self-supporting fibred wall that closes over into the roof, with no frame and no formwork. Developed in Brittany by Évelyne Adam. A kerterre can be an addition to a house, such as a garden shed, or one of several small buildings that together make a household. A basic kerterre is about 3 m across and takes about €500 of materials; the Twiza network puts a 9 m² one at three weeks for one person without machinery, and the largest built is about 5 m across. It has lasted in a wet climate: the oldest, in Brittany, is over twenty years old and reported free of leaks and cracks. The conditions matter. The walls stay damp for one to two years while the lime cures, so the build has to finish at least two months before the first frost, and the first winters need heating and ventilation. The render decides how the wall handles rain: research on hemp-concrete walls left outdoors found the outer coating must let vapour out while keeping rain from soaking in, or the wall stays wet.

Build it

No build tutorial recorded yet.

Cost: Low
Upkeep: Occasional
Skill to build: Intermediate
Lifespan: The oldest kerterre, in Brittany, is over 20 years old and is reported free of leaks and cracks although it is neither lived in nor maintained (kerterre.org FAQ; 18h39, 2020).
Embodied carbon: Low
Space / material use: High
Output timing: None
Skill to repair: Basic
Regulation (FR example): Size decides the formality. A construction of 5 m² or less of footprint and floor area needs none (Code de l'urbanisme, art. R421-2); one over 5 m² and up to 20 m² needs a déclaration préalable (art. R421-9); anything larger needs a permis de construire (art. R*421-1). The commune's PLU zoning still applies: outside a constructible zone, a new dwelling is generally refused.

Inputs

none

Outputs

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How does this solution compare to others for the same need?

Compare building and maintaining complexity, as well as efficiency where possible.

Solution	Skill to build	Upkeep score	Efficiency rank
Light timber frame construction	Basic	2	N/A
Post-and-beam heavy timber frame	Basic	2	N/A
Cob / monolithic earthen wall construction	Intermediate	2	N/A
Compressed earth block (CEB) walls	Intermediate	1	N/A
Rammed earth (pise) wall construction	Intermediate	2	N/A
Adobe / mudbrick walls	Intermediate	2	N/A
Superadobe (earthbag construction)	Intermediate	2	N/A
GREB straw wall technique	Intermediate	1	N/A
Vault or dome shell (walls and roof in one)	Intermediate	2	N/A
Kerterre (small hand-sculpted hemp-lime building)	Intermediate	2	N/A

Build skill and upkeep burden are proxies (lower burden = simpler to maintain); the efficiency column is this sub-function’s ranking, 1 = best. “N/A” where an axis isn’t rated here.

Sources

What this page does not tell you

No sizing or quantities: how much a technique yields, and how much a household needs, both depend on the build and the people, so the catalogue compares options rather than dimensioning them. It carries no bill of materials and no build sequence, and it is written for an oceanic, clay-soil climate (Normandy, France). Regulatory notes are indicative and need confirming locally.