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Green Advocate

Rammed Earth: Creating a 500-Year House

A design/build team demonstrates the durability of an ancient material

The rammed-earth construction technique is several thousand years old and is thought to have originated independently in both China, where original rammed-earth sections of the Great Wall are still standing, and the Iberian Peninsula. Other examples include the Fujian Tulou—a series of five-story round apartment buildings in China—and the Alhambra palace in Spain.

The technique has a lot to recommend it. The green-building benefits of rammed-earth homes can include low embodied energy, recyclability, high thermal mass, low energy loads, and nontoxicity. For those reasons, Terrell Wong, principal of Stone’s Throw Design in Ontario, Canada, is a fan of the material and the method. She also appreciates the durability and longevity of rammed-earth houses. When describing rammed earth to her clients, Wong says, “It is the structure, the insulation, the finish, and the thermal mass for a building. It will never need painting, and it will last 500 years, if not more.”

For the past 10 years, Wong has designed three to four rammed-earth houses per year. She says it’s still something of a fringe method in Canada, and notes that there are just a few builders doing rammed-earth construction in all of Ontario. One of them is Sylvia Cook, principal of Aerecura Rammed Earth Builders. Though rammed earth is often said to work best in arid climates, Cook makes this point: “The thermal-mass effect works equally well for hot climates, where heat gain is delayed, and for cold climates, where heat loss gets shifted from the middle of the night to the middle of the day, when the sun makes up the difference. This keeps the temperature consistent year-round.” In other words, when used correctly and in conjunction with climate-appropriate passive design, thermal mass moderates internal temperatures by averaging out day−night extremes. This increases comfort and reduces energy…

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6 Comments

  1. CarsonB | | #1

    Surprised to hear a wall was done in 24 hours, the one Risinger toured in Texas was taking over a year just to put the walls in as I recall. What was the budget of the affordable housing project, and the square footage of the rammed earth walls used? Perhaps this will be a more viable replacement for concrete if robotics start to take a larger role in construction.

    1. User avater
      Stephen Sheehy | | #3

      The walls use a lot of cement, so I'm concerned about embodied energy, compared to a typical wood framed house.
      It looks great. I love to see cost data. I suspect this house was much more expensive than a typical wood house.

  2. Expert Member
    Malcolm Taylor | | #2

    The walls are really beautiful, and must be nice to live with.

    I wonder about a few things:

    - There doesn't to be any capillary break, so in non-arid climates that may be a problem.

    - The article mentions seismic resistance, but only in reference to brick or block walls, which typically don't do very well in an earthquake. The comparison is also with a monolithic rammed-earth wall, but the ones shown are separated by a thick layer of insulation in the middle, which will significantly reduce their strength. They don't look suitable for high-seismic areas.

    - How do rammed earth walls "enhance the passive ventilation"?

    - Why is reinforcing only necessary in "colder, wetter climates"?

    1. Brian Cade | | #5

      1. Any "good" rammed earth design will incorporate HUGE overhangs to cover bulk water. From there you could create a break at the insulation layer, though because of the ramming process there will be no air gap. There are also various clear sealers that can be applied to either face to mitigate many of the downsides of it being so porous. Not great solutions, but that's what I've seen.
      2. When using embedded insulation you're effectively building two walls. Presumably you could tie the two together and somewhat reduce material use, but finding a structural engineer that would sign off on something like that wouldn't be easy.
      3. No comment
      4. I'd venture a guess that anything load bearing nowadays would need (by virtue of the SE) both cement and reinforcing. It sounds like the Canadian method mentioned may get around that.

      *This is based on my recollection of reading The Rammed Earth House by David Easton and everything else I could find on the subject a few years ago, so take it with a grain of salt.

      1. Expert Member
        Malcolm Taylor | | #6

        Brian,

        The Cobb, Rammed-Earth and Straw-Bale houses around here always rely on volunteer labour in some form. The most usual method is to run a workshop where the participants help build in return for the education they are receiving. They all create very captivating houses, but face unsurmountable obstacles to come mainstream techniques that can compete with wood frame structures.

        My concern in #1 was more with a capillary break at the bottom of the wall to combat what the British call "rising damp". Incorporating one might not be that difficult, but it would certainly be an essential part of any rammed-earth house built in the PNW.

        I'd add to my list of questions: How did they come up with it being a 500 year house? These claims on the longevity of projects have been a bit of a theme in recent blogs. It would be nice to have the article include something to explain how they arrived at the number. Why isn't it a 200 year house, or an 800 year one?

  3. Brian Cade | | #4

    Please explain how a two foot thick wall with 5-10% portland cement content qualifies as a green product? Hell, you could build the thing out of concrete and have less embodied energy, not to mention a FAR more durable surface, use dramatically less labor, and still more than enough thermal mass to regulate the interior.

    Rammed earth is up there with green roofs in terms of greenwashing nonsense. Unless you're in an arid third world country (effectively free labor and no building codes) it has virtually no functionally valid uses. I'd expect this from a site like Inhabitat, but not GBA.

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