Vault or dome shell (walls and roof in one)

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

Suitable earth on site, and a plan for keeping the shell dry: in a wet climate its protective render has to be renewed every few years, or a roof built over it.

Walls that curve over into the roof as one self-supporting earth shell, so the roof needs no timber and no metal sheeting. Documented ways to build one: the Nubian vault, sun-dried earth bricks laid at about 45°, which lets the vault rise without any temporary support; compressed earth blocks laid free-spanning, which the Auroville Earth Institute has taken to a 10.35 m span; and earthbag domes, coiled course by course (see superadobe). Because the roof itself is earth, keeping it dry decides how long it lasts. A lime-stabilised earth plaster kept Auroville's vaults dry through 402 mm of rain in five days, but its additives broke down in sunlight and it let water through after about five years. Earth left bare erodes slowly: twenty years of a wet continental climate took about 6.4 mm off unstabilised rammed-earth walls and about 2 mm off walls with 5% lime. In a wet climate, plan to renew the render, or to keep the shell under a roof.

Build it

wiki.lowtechlab.org/wiki/Superadobe FR

Cost: Low
Upkeep: Occasional
Skill to build: Intermediate
Lifespan: About 50 years expected for a Nubian vault, against under 10 for the metal-roofed earth houses it replaces (Wikipédia); unstabilised earth walls in a wet continental climate have an extrapolated lifetime of more than 60 years (Bui et al. 2009), provided the shell's render is kept up.
Embodied carbon: Low
Space / material use: High
Output timing: None
Skill to repair: Basic
Regulation (FR example): Part of the structure or footprint: covered by the building permit (permis de construire) for a new dwelling. Rural sites are additionally constrained by the commune's PLU zoning, outside a constructible zone, a new dwelling is generally refused.

Inputs

none

Outputs

none

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.