Flying Concrete Ferrocement Houses

Flying Concrete ferrocement house

Ferrocement is resource efficient because it uses minimal rebar and concrete to produce ‘thin shell’ structures. The resulting curved members are somewhat similar to trees and plants. This is the opposite of straight concrete walls that rely on massive thickness to gain strength (and cost way more money).

One of the best sites for learning about ferrocement is Steve Kornher’s Flying Concrete website. Steve has gone to great lengths to provide lots of photos and detailed information about ferrocement.

Ferrocement can be used to create many things, including boats, cisterns, stairs, and roofs on earthbag domes and earthbag vaults.

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Nubian Vaults in Africa

The Nubian vault is an African technique for the construction of timberless vaulted roofs. The AVN (Association la Voute Nubienne), through its Program ’Earth roofs in the Sahel’, helps provide families in sub-Saharan Africa with comfortable, sustainable, affordable, homes.

In a recent Newsletter from this organization, I was impressed by the statistics they provided regarding the impacts of their program:

Since the start of the program, 1309 vaults have been built by Nubian vault masons and entrepreneurs, for 533 clients, in 244 locations (villages, hamlets, towns) in 5 countries (Burkina Faso, Mali, Senegal, Zambia, and Madagascar). If all the vaults built were to be placed end-to-end, this would reach a total length of 9.7 km.

In total, 214  masons have been trained, of whom half are at the foreman and/or entrepreneur level ; and there are currently 296 apprentices in training.

10,000 people use, live in, or sleep in Nubian Vault buildings; of the total built, 85% are for private houses, and 15% are community-use buildings.

Approximately 18,000 trees, 25,000 tonnes of CO2-equivalent, and approximately 15,000 corrugated iron roofing sheets have been saved as a result of NV construction, as compared to the alternatives.

Approximately 750,000 Euros of local economic impacts have been generated by the program.

Since 2000 the program has experienced an average annual growth rate of 36%.

We at www.earthbagbuilding.com have been cautious about recommending the construction of vaulted roofs using earthbags because of issues with stability. Using small and solid brick units for construction does make this sort of vault possible. I would still be cautious in suggesting that people follow the lead of Nubian Vault construction in climates where there is any danger of moisture soaking into the mud bricks and causing the vaulted roof to fail. But in sub-Saharan Africa this is obviously a very viable alternative to other roof systems. In wetter climates, the use of fired or otherwise stabilized bricks is also possible.

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Finca Luna Nueva Lodge Workshop

The Finca Luna Nueva Lodge in Costa Rica is a sustainable rainforest eco-hotel together with a certified organic biodynamic farm. They began farming  in 1993, planting and harvesting organic ginger and turmeric. They just finished a workshop building an earthbag roundhouse, and plan to do at least one more. You can find out more about them on their Facebook page, and see many more photos  here.

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Most Popular Earthbag Instructables

Visit Instructables.com for the best how-to articles on a wide range of topics, including earthbag building.

Instructables.com is one of my favorite sites and so I’ve been publishing how-to articles there for the last year or so. Here’s a list of the most popular Instructables on earthbag building.

How to Build an Earthbag Dome
Step-by-Step Earthbag Building
How to Build an Earthbag Roundhouse
How to Build Dirt Cheap Houses
How to Build an Insulated Earthbag House
Insulated Earthbag Foundations for Yurts

Total number of views as of October 25, 2011: (click on author link… now about 342,000)
Coming soon: A new Instructable on Cool Pantries.

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All the Best Earthbag Content

For several years, Kelly and I have been filtering all the best earthbag content from the Web, writing extensively on all aspects of earthbag building and organizing the information for readers. There’s now an enormous amount of information available – so much that it’s difficult to keep up with everything. That’s one reason why our sites are helpful. We gather the best information so you don’t have to spend endless hours looking for it, wasting time clicking through low quality sites, blurry videos, etc. No one else has anything close to this amount of content. Below are just a few links from EarthbagBuilding.com (the mothership) and our Earthbag Building Blog. Also note how we strive to keep all these pages up to date so readers aren’t faced with a bunch of broken links. (And it’s free.)

Earthbag Projects and Pictures
Earthbag Videos
Earthbag Articles
Earthbag Testing
Earthbag Blogs (recently updated and expanded to include earthbag blogs in Spanish)

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Top 10 Most Popular Earthbag Blog Posts

Instructable: How to Build an Earthbag Dome by Owen Geiger

Every year we publish the most popular blog posts for the last 12 months. We’ll do that again in November on our 4th anniversary. Our goal here is to look at the most popular blog posts since we’ve started – the Best of the Bestest. Think of them as hidden gems unless you’ve read all 756 blog posts. (And if you have read them all, then you can start reading the info on our mothership at EarthbagBuilding.com. It’s all free. Enjoy.)

1. Counties with Few or No Building Codes
2. Bullet Resistance of Compressed Earth
3. Low-cost Multipurpose Minibuilding Made With Earthbags (This is my earthbag dome that almost went viral last year and got republished on dozens of blogs… see photo above.) Click here to read the free Step-by-Step How to Build an Earthbag Dome Instructable at Instructables.com.
4. Creating Earthbag House Models
5. Earthquake-resistant Earthbag Houses
6. Earthbag Rootcellar
7. Cost of Earthbag Houses
8. $2,000 Earthbag House
9. Earthbag Survival Shelter
10. Using Earthbags as Ceiling Insulation

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Lightweight, Insulating Geopolymer Earthbags Part 3

Stone House by Askjell (click to enlarge)

I’m proposing using a combination of ferrocement, earthbags and porous geopolymer to build durable, affordable housing. In a nutshell, earthbags filled with lightweight geopolymer cement are fastened to a rebar or bamboo frame and then plastered with geopolymer cement. This is distinctly different from heavy earthbag walls, and much different than regular thin shell ferrocement that often does not provide sufficient insulation and lacks the visual appeal of houses with substantial walls. The end result would be an incredibly durable stone home made with natural materials.

First, let’s do a quick recap of Part 1 since it’s been a few months (wow, time flies) since I posted my first thoughts.
– Geopolymer is highly desirable because it’s an affordable, natural material that turns to actual stone and is fireproof, insect proof, rot proof, bulletproof and can last for centuries.
– Geopolymer is superior to Portland cement in a number of ways: far lower carbon footprint, less cracking, more resistant to corrosive elements such as sea salt, excellent frost resistance and durability in cold climates, rapid set binders available.
– Porous geopolymer is light weight, easy to work with and insulating. No additional insulation is needed.
– Recycled waste materials such as slag and fly ash can be used to make geopolymer, thereby making the material carbon neutral.

In Part 2 I posted a close-up photo of porous geopolymer and covered a few of the building basics: minimal tamping required, smaller diameter bags or tubes save materials, a keyway can be formed to lock courses together, flatten walls to reduce plaster work, bag material could be removed before plastering or left in place.

Now, on to Part 3. Here is the summary of the basic concept:
– Build a rebar or bamboo and mesh frame to guide the shape. This provides plenty of tensile strength and enables almost limitless design possibilities.
– Use tubes or bags to form walls 6”-15” thick. These could be made out of a wide range of materials, including polypropylene (typical sand bags) or natural materials such as cotton, jute, etc. Tubes would be faster than bags. Recycled bags may be available and less expensive than tubes. Mesh material will provide superior bonding with the finish coat and eliminate need to remove the bag material before plastering.
– The wall thickness depends on the climate and other considerations. Use thicker walls in colder climates where more insulation is needed.
– Fill the tubes or bags with lightweight, insulating geopolymer. The consistency would be similar to ‘stiff’ (not too much water) pumicecrete (pumice-crete).
– Pumicecrete is a standard product and provides a good point of reference, although many similar materials could be made using geopolymer mixed with different insulating materials in addition to scoria/pumice: perlite (perlite cement), shredded recycled polystyrene, vermiculite, etc.
– Porous geopolymer (lightweight aerated cement or concrete) can also be made with a foaming additive to produce tiny air bubbles in the cement. Porous geopolymer can be used alone or combined with scoria or other materials.
– Porous geopolymers have unique passive cooling properties which can improve thermal performance and reduce the heat island effect in cities.
– Tie the tubes or bags to the frame as they are filled.
– Flatten the tubes or bags slightly as they set up. This will greatly reduce plaster work.

Key advantages:
– No need for contractors or industrial size compressors and high-pressure spray rigs. Finish plaster can be sprayed on with a Mortar Sprayer.
– Nearly limitless design possibilities as mentioned above.
– This method has the advantages of ferrocement and earthbag building without any major drawbacks that I can think of: 1. faster construction and less labor than earthbags; 2. more substantial, bulletproof and more insulating walls than ferrocement.
– A second ferrocement frame could be added for seismic regions, but it shouldn’t be needed in most situations.

Part 4 will discuss how the building process can be mechanized to speed construction.

Note on the photo: I chose this photo to illustrate how almost any shape can be built — from ‘boulder houses’ like this to conventional looking structures of all kinds.

Image source: http://askjell.deviantart.com/ and http://fc01.deviantart.com/fs20/i/2007/230/5/3/The_stone_house_by_Askjell.jpg#elf%20house

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Disaster Resistant Catenary Domes

Disaster Resistant Catenary Dome (click to enlarge)

Specifications: 314 sq. ft. interior, 181 sq. ft. interior loft, total = 495 sq. ft. interior, Footprint: 23’ diameter

This blog post is a continuation of the discussion about disaster resistant domes. So far we’ve talked about Hemispheric Domes and key ideas about How to Build the Strongest Buildings That Can Last Centuries.

Wiki describes a catenary arch as “the curve that an idealised hanging chain or cable assumes when supported at its ends and acted on only by its own weight.” A catenary arch can be inverted to define and guide the shape of a dome (a dome is an arch that’s been rotated about its axis). This creates an incredibly strong shape, that when combined with the right materials can produce structures with superior disaster resistance.

The idea for this design sprang from a reader who liked the disaster resistant building concept, but wanted a taller dome with a loft. Well, here it is.

More details at my Earthbag House Plans site.

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Hobbit House with Wood Shingles

Hobbit House with Wood Shingles (click to enlarge)

My Hobbit House design was one of the top viewed earthbag plans last week, and one of the most common search terms, so I reworked the roof to incorporate wood shingles. The first version showed a living roof, but these take a lot of maintenance and require an expensive EPDM rubber membrane. A wood roof is probably more practical for most people.

This alternate version uses a double pole roof to provide ample space for roof insulation. Inner and outer roof poles are bolted to steel compression rings like in my earthbag roundhouse. This enables you to bolt the entire roof together in a few hours. Wood shingles are practical and well suited for this curved (undulating) roof design. Loft height in the center is 8′.

This design also works perfectly if you want to build one structure at a time as you can afford it. I’ve talked about this repeatedly. It’s the best way to go in my opinion to keep costs low. It saves trying to build a larger house all at once. It means you can build without a mortgage — work in stages as you can afford it and as weather allows.

Roundhouses are the easiest shape to build in my opinion. Roundhouses can be built side-by-side, connected by joining structures (vaults, etc.), pergolas, or set apart separate from each other. Plan ahead if the units are joined. You don’t want to cut out doorways later due to lack of planning.

Hobbit House at Earthbag House Plans

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Good House, Nice Body

Kimuma Watanabe is a Japanese architect and Associate Professor at Kochi University of Technology in Japan. He has been involved in many projects with earthbags around the world. One of his smaller projects is an installation of a demonstration dome featured in these photos. The Japanese aesthetic and precision is obvious in the way the bags are assembled and tamped. For more about Kikuma and his work see this post.

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