Important Facts About Stabilized Earth
We're glad you're considering using stabilized
earth for the walls of your project. When you take into account
energy efficiency, environmental responsibility, price, comfort,
longevity, inherent beauty and architectural power, there is simply
no better value in today's construction market.
But before you make the final commitment to build with earth,
there are a few important points you need to think about. The
advantages, of course, are numerous and we've taken the opportunity
of describing them for you below. There are also certain characteristics
of the walls that some people think of as limitations (although
to others these same features are considered enhancements). It's
critical to us that you be fully aware of these characteristics
so that if you do build with earth both your experiences during
construction and your appreciation of the finished product will
be as rewarding as possible.
Thermal Flywheel Effect
The ability of a solid earth wall to store energy
for long periods of time results in interior temperatures that
change very little from day to night. Mass walls absorb solar
energy during winter days and then re-radiate that energy to offset
nighttime heat losses within the building. In the summer months,
the mass of the walls absorbs excess heat generated during the
day, keeping the inside spaces surprisingly cool, then releases
that stored heat to the clear night sky. In a properly designed
and oriented building, this can mean significant savings in heating
and cooling bills. And because the energy that controls the temperature
inside the building radiates directly from the mass of the walls,
the quality of the comfort inside is noticeably different than
in a space regulated through mechanically altered air. Couple
a mass wall with a hydronic radiant slab to achieve the most quiet,
uniform, and dust-free heating system available.
Indoor air quality
Unlike wood-frame buildings, earthwalls do not
outgas hazardous fumes. An earth walled building with a natural
finish emits no toxins, and in combination with soil-cement flooring
warmed by radiant tubing, the indoor air is superior to most other
buildings on the market.
Longevity, durability, and low maintenance
Walls built of raw earth in China, Africa, and even
the cold wet climates of northern Europe continue to provide shelter
after several hundred years of use. With the addition of modern
stabilizers, concrete foundations, and steel reinforcing, we can
say in total confidence that our earth walls will last for many
centuries. And like all other masonry wall systems, whether they
are brick, stone, or concrete, exterior maintenance is virtually
Fire and insect resistance
Two important reasons for choosing to build with
solid earth walls are that they are fireproof and resistant to
damage from termites and other insects. Both these factors contribute
to greater longevity, of course, but they can also mean an important
increase in safety for you and for future occupants
One of the most appealing aspects of a house with
thick earth walls is the indescribable feeling you get just being
inside. There is a certain calmness that simply can't be duplicated
with lightweight building materials, no matter what the architecture.
Whether it is simply the energy of thermal mass, the healthful
air of a natural environment, the quiet that results from the
sound absorbing nature of the solid earth, or some other less
identifiable quality, there is something special about an earth
Perhaps the best reason to build with earth is the
boost it can give to the health of the planet. Earth is an unprocessed,
widely available building material with virtually no side effects
associated with its harvesting or use. Since an earth walled building
saves construction and energy resources, doesn't pollute, and
lasts practically forever is a wise investment in the future of
The Frequently Asked Questions
The first question people usually ask about earth
walls is, "How do they respond to earthquakes?" The
answer is that earthquake safety is our number one concern. In
fact, it was the very first engineering task we addressed twenty
years ago when the modern renaissance of rammed earth began. Today,
there are several different design approaches we employ depending
on the design of the building, the method of construction, and
the proximity to an earthquake fault. In some cases, individual
panels of earth are enclosed within a framework of cast-in-place
concrete. In others, the earth walls are fully reinforced with
an integral grid of steel reinforcing rods. A third approach is
a continuous solid earth wall topped with a bond beam of reinforced
concrete. Whatever the engineering design, every wall system is
in full compliance with local building codes, including projects
built in seismic zone four localities. Each is constructed to
the highest standards of workmanship and quality control.
The second most frequently asked question is, "What
happens when it rains?" The answer is that if the soil is
selected properly and the wall constructed according to specifications,
the finished product is as resistant to deterioration as the parent
rock from which the soil came, and in some cases even more so.
Tests conducted on samples of finished walls demonstrate that
stabilized earth can be completely saturated for months at a time
without any deterioration whatsoever. Because not all soils are
ideal, and because earth loses its insulative properties when
it becomes wet, in climates where rainfall can be extreme, walls
should be protected against saturation with ample roof overhangs
and raised foundations.
What about Radon?
Radon is in fact never confined to any one soil
but rather originates deep underground in certain rock formations
and passes directly through the mineral soil and the top soil
as it escapes to the atmosphere. Radon is of concern when air
tight houses are mistakenly constructed on top of these formations.
How much do they cost?
Houses with walls of solid earth will cost slightly
more than a comparably designed house with wood-frame walls. As
explained above, they are both a better product and a better investment.
How much more they cost will depend on your site, the height and
complexity of the wall system, the available soil, and the seismic
safety factors. Generally the cost increase ranges between 5%
The Nature of the Process
Stabilized earth construction, whether it is traditional
rammed earth or the new PISÉ process, is still a made-by-hand
product. As such, it exhibits all the inconsistencies and variations
that characterize any handmade item.
The color and texture of the finished wall will vary from spot
to spot. Some areas may be rough and less well-consolidated than
others. Shrinkage cracks, honeycombing, and voids are inevitable.
Tolerances for line and level are typically more forgiving than
for manufactured building materials. In short, a brand new earth
wall looks old the minute the formwork comes off.
For the homeowner who desires this old world look, earth walls
are a natural. To one who seeks the comfort, security, and energy
efficiency of affordable thermal mass, without the patina of antiquity,
a wide range of washes and plaster finishes can be applied to
the interior wall surfaces.
The truth is, the way the walls look straight off the formwork
may not be to your liking, and we recommend that you include the
price of a plaster finish in your construction budgeting. If,
as the rest of the building takes shape, the natural finish walls
enhance the look of the interior in your eyes, then the money
reserved for plastering can be invested in some other upgrade
to the building finishes.
In some cases, especially when walls are constructed
during wet, cold weather, free lime in the soil mixture can migrate
to the wall surfaces, causing a powdery white stain to appear.
Efflorescence can be minimized during the curing process by covering
the walls with polyethylene if prolonged wet weather is anticipated.
Although it is difficult to remove completely, a washing with
a mild muriatic solution will greatly reduce the staining.
Stabilized earth walls, like rock, are slightly
porous. In arid regions, the exterior surfaces should require
no waterproofing whatsoever. In areas where snow or wind driven
rain can be severe, moisture may penetrate all the way to the
inside surface of the walls during prolonged storms. In these
regions, we recommend sealing the exterior walls, either all of
them or only those which are expected to take the brunt of the
storm and are not adequately protected by roof overhangs.
Interior wall sealing
For ease of cleaning and to retard dusting, a clear
penetrating sealer should be applied to all unplastered interior
walls. Ramseal is a product specially formulated for use on earthwalls.
Other water-based sealers (such as Glaze ‘n Seal) are readily