Wooden Shakes on Earthbag Houses

Wooden shakes on domes

Wooden shakes are a sustainable roofing material because they can be made by hand using a froe and locally available wood. You can make shakes from many kinds of wood, but the best shakes come from old trees with tight growth rings. Install shakes over roofing felt, and fasten with galvanized roofing nails. Steep roofs of 5:12 pitch or more will reduce risk of leaks and wind damage.

Wooden shakes can be used on walls and roofs built of pallets. See Pallet Roofs

Here’s a good article by Mother Earth News magazine on making wooden shakes:
The Froe and You: How to Make Hand-Split Shakes

Earthbag Basements

So far very little has been written about earthbag basements. Earthbags are suitable for basements and other underground applications such as cisterns and rootcellars. Round or curved designs are inherently stronger than long, straight walls, which require reinforcing columns or buttresses.

Earthbag Basement Wall Detail

General guidelines for earthbag basements:
- 24″ wide poly bags (measured when empty)
- lime stabilized soil tamped solid
- 10%-20% type-S lime hydrate to dry soil by volume
- mix lime and soil thoroughly before adding water
- two strands 4-point barbed wire
- rubble trench with French drain
- taper walls slightly outward
- double layer 6 mil polyethylene moisture barrier
- use scoria, pumice, etc. for improved insulation

Build on high ground, and grade the site away from the building. Dry climates are obviously more suitable than wet climates. Use caution — working below grade is dangerous. Temporary shoring may be required. Avoid problem clay soils. The final design should be based on soil tests and calculations by a licensed engineer.

I have one plan with a basement: Habitat Earthbag House

Some Thoughts about Durability and Financing

Jorge Dominguez has been building earthbag  houses in Hawaii for  some time, and he recently emailed me some of his thoughts about this way of building as it relates to durability, financing, and insurance. I think that he has touched on some very important issues that I would like to share with you.

“I was originally against asking banks for financing for earthbag structures. I don’t think I am going to do it for my experimental home on the Big Island, but I think that for bigger projects there is no way to do them without some kind of loan from a bank. My guess is that if I ask for a loan for an earthbag building, it is going to get rejected in 5 minutes.  They don’t care much about the process of building and the environmental benefits of earthbags. All they care about is the bottom line, whether they can make a profit or not.”

“The current real estate meltdown is proof that something is inherently wrong with the way homeowners get financing from banks. It seemed like almost everyone was playing a speculators game with homes that were not meant to last long. It appears that banks favor building with economies of scale using prefabricated materials. Sure, this way of building can guarantee low costs in the short run, provided that transportation costs do not rise that fast. Crossing fingers that oil prices will not go over the roof can make this model look good. But what nobody seems to be questioning is how long do these homes built with prefabricated materials last.”

“The typical definition of homeowner is somebody who gets financing from a bank, and moves in with his family to the new home after having been approved for a loan and giving a small deposit. But let’s be realistic: this is not owning a home, more accurately you are a home debtor.”

“Banks should give priority to homes that have a long life. If your home begins to deteriorate in 20 years, we cannot call that a fixed asset. A big incentive for owning a home is  creating value for your descendants. What is the point in signing up for a 30 year loan, if the home is going to last only 20 years? Sure, someone can tell us that you can extend the lifetime of a home with the proper maintenance, but is it common to see a home that lasts 100 years? What about ancient culture’s way of building? With very little technology, there is living proof of still standing structures built by the Aztecs, Greeks, Romans, Mayans.”

“We would like banks to start financing earthbag building, because not only it is environmentally correct, but it is a super durable material. Banks should not focused entirely on the big guys with their economies of scale. They should think outside the box, and provide funding for do-it-yourself builders. Earthbag or super adobe building is extremely economical on materials. The only real costs are the hauling of earth, sand and gravel short distances. These materials are so abundant in nature that there is no risk of depleting natural resources like is the case with wood.”

My sister who also lives in Hawaii and is a professional real estate appraiser had this to say on these issues:

“I agree with you whole-heartedly about the sustainability issues around earthbag and other alternative building practices.  It does seem crazy to build with wood where the moisture levels are so extreme, and termites are prevalent.  All the lava is used for rock walls, and I haven’t seen one home made out it. I have seen first hand what a short time of negligence can do in this climate to traditional homes.”

“Unfortunantely, what the banks are looking for is conformity and security, especially now with the mortgage crisis that is still spiralling down here, with tons of short sales and foreclosures and more yet to come.  Of the properties for sale in my subdivision 40-45% are distressed properties.”

” Conformity is good for banks and appraisers because it makes comparison simple and is a good way to conclude value.  Examples of homes that are considered to be less market approved of are A-frame homes, domes, and those built with alternative building materials.”

“County codes and regulations are a kind of Bible for banks and if the local planning department accepts a building it is considered to be okay.  In approaching a bank for a loan on an earthbag home your best bet is to have as much blessing and documentation from the planning and building departments as you can get.  You will be more likely to secure a loan if you have more than 20% down payment.  No doubt the loan will be at a higher interest rate due to “risk” factors of market acceptance, and you will not get the loan amount that a conventional home would.  Domes, for instance, require a discount in the appraisal for what is called “functional obsolescence” which means most buyers would reject it.  It therefor is not as functional in the arena of buyers and sellers.  This discount can be 10% of the value or more, so you would have to anticipate this.”

“There are more signs that the green movement is becoming more mainstream.  There are now classes for appraisers about green homes and commercial buildings and it is gaining momentum.  Accepting alternative materials is a next step.”

Cost of Earthbag Houses

One of the most frequent questions people ask is how much do earthbag houses cost? It’s a little difficult to answer because there are many factors that affect the total cost. A lot depends on what features you want to add, whether or not you have building codes, how much work is done by the homeowner, and the details of the building itself.

A small, simple house made of natural building materials could be built by a DIY builder for about $10/sq.ft. This assumes doing most everything yourself and using the low-tech building ideas explained on our websites. It doesn’t include things like land, building permits and utility hookups, since the price of these things vary wildly.

Keeping in mind it is much easier and lower cost to build with earthbags in rural areas with minimal building codes, let’s look more closely at one example. Here are the approximate costs of a 15’ interior diameter roundhouse with earthen plaster and floor, recycled materials where feasible, and reciprocal pole roof with sod on top.

Recycled earthbags @ .20/bag = $108
Soil = $100 (bag fill, plaster, floor)
Gravel bag foundation = $20
Barbed wire = $35
Roof poles = $25 (with firewood permit from national forest)
Salvaged barn wood roof decking = free
6 mil poly = $25 (for roof)
Reinforced concrete bond beam = $100
Doors, windows, hardware, bathroom fixtures, tile, etc. from yard sales/barter = $175
Sod = free
Plumbing/electrical = $200
Composting toilet = $20
Earthbags w/rice hulls ceiling insulation = $10
Reed mat ceiling = $40
Recycled wood for cabinets = $100
Nails, screws = $42
Total cost = $1,000

This works out to be less than $6/square foot for this 176 sq. foot roundhouse in a non-code area. I’m sure I’m forgetting a few things, but you could double this cost to cover gas and any extras and still have a nice little house for $2,000. Now you can see why we’re so excited by earthbag building. It’s a real game changer for those in need of affordable housing.

Living Walls

I recently wrote an article about living walls for GreenHomeBuilding.com, and in doing the research for this I came upon an interesting approach to creating a kind of living wall or retaining wall using geotextile materials. Basically, loosely woven bags filled with a growing medium can be stacked to form walls that then support plant growth.

One company in particular, www.filtrexx.com, has been selling various systems for doing this for some time. This is a green alternative to hard-faced walls, and can create walls that are either completely vertical or slope up to 2:1. A variety of vegetation can be supported this way, depending on the location and purpose of the wall. They say that this is faster to install than conventional block materials used in retaining walls.

But if you look at the basis of the concept, it is not that different than building with earthbags: bags of material are stacked to form walls. But in this case, the bags are then protected by the plants that grow out of them, and this vegetation becomes the exterior interface with the environment, providing oxygen, filtering the air, and looking beautiful.

So how might this idea be utilized for buildings? Obviously the main issue is the moisture that inevitably will migrate into and through the wall to the interior space…unless there is some way to stop it.

One approach might be to build the earthbag structure as is frequently done, with compacted soil, and then cover this with a waterproof membrane to protect it from intruding moisture. A second skin of a “living wall” could then be applied over the membrane, both as protection for the earthbag structure, and as an insulating layer.

This would create the ideal situation for climate-responsive housing, where the inside is composed of thermal mass materials, and the shell of the structure is insulated to keep the interior from loosing its comfortable temperature.

Besides using the geotextile bags, it is also possible to use one of the variety of systems that have been devised for creating living walls that are attached to buildings, as shown above. Many of these sophisticated systems automatically provide the necessary water to maintain the plants, so there is very little maintenance over time.

Earthbag History Footnote

We want to thank Doug at http://www.dailykos.com/story/2009/7/18/754890/-NFTTFill-The-Sandbags!-Edition for providing us some additional information on the history of sandbags (earthbags).

Doug has kindly informed us that sandbags can be traced back almost 250 years to the Napoleonic Wars, during which time French troops were issued sandbags for use in the field.

And as you can see in the photo below, sandbags were also used in the Civil War. Thank you Doug for this fascinating information.

A sandbagged military position during the American Civil War.

Reciprocal Roofs

Ziggy has the best info I’ve found on reciprocal roofs at his Year of Mud website. See: How to Build a Reciprocal Roof Frame

Reciprocal Roof

A reciprocal roof is a simple self-supporting structure made of poles or dimensional lumber that are arranged in a spiral pattern. No center support is needed. They are perfect for round buildings. Developed by Graham Brown in 1987, this type of roof is extremely strong and can incorporate a living roof of plants. They’re fast to build. A reciprocal roof on a small house can be erected in a few hours. It is also affordable, since it can be made with peeled poles from a local forest. (Poles can be gathered with a low-cost firewood permit, typically costing around $25 or so.)

The basic process involves bracing the initial pole called a Charlie stick and then working either clock-wise or counter clock-wise, placing and tying poles in position. The last pole goes over the previous pole and under the Charlie stick. Then, just knock out the bracing under the Charlie stick and the frame is self-supporting. Secondary rafters can be added between primary rafters.

Check out Ziggy’s site for pics and complete details. He even provides a good list of resources for further reading.

Earthbag Building in 35 Different Languages

I am pleased to announce that www.earthbagbuilding.com is now available online in 35 different languages. With the simple addition of a Google “Translate” box as part of the main menu, you can now choose to read all of the text on any given page in your language of preference. Once the new page is created (it only takes a few seconds), then the entire site can be browsed via the standard menu and all subsequent pages are also presented in translation. Amazing!

This should make the information more accessible to the millions of people around the world who might benefit by it.

Cold Climate Earthbag Yurts

There’s great, untapped potential for superinsulated earthbag buildings in cold climates. Here’s a way to combine the best features of earthbags and yurts. The basic idea is to combine earthbag walls filled with lightweight insulation such as scoria (lava rock), with a traditional yurt roof frame that’s insulated with perlite or vermiculite.

Yurts (ghers) have been used in Mongolia and other areas for centuries. Traditional yurts are well suited for cold, windy places, in part because the wind just blows around them. They can, however, be made even more comfortable with extra insulation in earthbags.

Scoria is perfect for superinsulated earthbag walls: low cost, all natural, rot proof, fireproof, doesn’t attract pests, lightweight and easy to work with. Scoria is great for building walls since the aggregates tend to lock together and form stable walls. Tie courses together with twine for best results, and then cover walls with canvas.

Yurt roof frames are readily available through numerous suppliers, and fast and easy to assemble. The steel tension cable is strong yet light. They are very resource efficient, using minimal wood, but often lack adequate insulation. I recommend tying bags of lightweight insulation to the bottom of the frame. Perlite and vermiculite would be excellent choices for ceiling insulation since they’re very lightweight.

This design is portable, just like traditional yurts. The entire structure can be disassembled and transported if necessary. This would be a dream structure for places like Minnesota, Canada, Alaska, Siberia and Mongolia because it would be super comfortable, inexpensive, portable, wind resistant, owner built and could be built in many sizes. Add a skylight, rocket stove, small solar panel and composting toilet and then you can laugh at the wind howling by.

Earthbag Privacy Walls

In addition to many other uses, earthbags also make great privacy walls. Besides being beautiful, privacy walls help block wind and noise, and keep out stray dogs and prying eyes. You can greatly enhance your home using this dirt cheap building technique.

Privacy Wall

Protected from excess wind, plants can thrive even in harsh climates like New Mexico. In fact, you can create a mini oasis behind privacy walls with proper care and adequate watering. I refer you to a great little book called Behind Adobe Walls: The Hidden Homes and Gardens of Santa Fe and Taos, by Lisl and Landt Dennis. They document through beautiful photographs of luxurious homes how thick earth walls shade plants in heat of summer and retain heat for nurturing many types of flowers and other plants through cold spells.

Unlike straw bale privacy walls that are susceptible to moisture damage, earthbag privacy walls can withstand the elements much better. They take more time to build, but you can make earthbag walls as moisture resistant as you would like by stabilizing the soil fill material with lime. Alternatively, you could experiment with building privacy walls of scoria, which is highly resistant to moisture damage, and lightweight and easy to work with.

And because earthbags are so versatile, you can combine earthbag privacy walls with planters, benches, arbors, trellises and garden walkways to create magical spaces that are only limited by your imagination.