Low-Cost Green Home
close-up of Pumice-Crete material
Photos courtesy of Pumice-Crete

Pumice-Crete

Pumice is an extremely lightweight rock formed when volcanic lava cools so quickly that most of its volume is comprised of tiny bubbles of trapped gases. Pumice-Crete is made of three ingredients: pumice as aggregate and just enough portland cement and water to hold the pieces of pumice together. The insulating value of Pumice-Crete comes from both the tiny bubbles within the sponge-like pumice itself and the larger air spaces between the pumice pieces, once the whole wall is sealed by a plaster coating. Pumice-Crete is poured into forms to cast walls in place, then a solid concrete bond beam is poured atop the walls to hold connectors for the roof system. With minimal wall thicknesses of at least 14 inches, Pumice-Crete is strong enough to need no additional structural support for most one- or two-story buildings.

pouring Pumice-Crete into forms
Advantages of Pumice-Crete:
  • Pumice-Crete walls are much more consistently insulated than conventional, stud-and-batt walls, and they allow far less air infiltration.
  • Pumice-Crete uses relatively little portland cement, and the pumice aggregate is collected from shallow deposits found in volcanic areas around the world. In many areas, all of the needed materials are available locally.
  • Pumice-Crete can be delivered pre-mixed in trucks or mixed on-site.
  • Unlike wood, Pumice-Crete will not burn, rot, or get eaten.
  • The uniformly coarse Pumice-Crete surface allows a stucco finish without the use of stucco netting.
  • The light weight of Pumice-Crete allows the use of lightweight forms, made of half-inch plywood and 2x4s, that can be saved for use on another building project.
  • Thick, poured walls allow for interesting architectural choices that highlight their massive, earthy quality.

For much more information, see Pumice-Crete.

Here is a completed Pumice-Crete house:

finished Pumice-Crete house