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bamboo and cordwood construction

Bamboo and Cordwood: Traditional Wood Framing Alternatives

By Tobias RobertsRise Writer
May 14, 2018

When most people think about new home construction, the first thing that comes to mind is a stick frame structure, with hundreds of 2x4s placed closely together that are then covered by sheets of plywood and Tyvek building wrap. Some professionals estimate that the framing process for home costs around 60 to 70% of the total cost of the house itself, and most homeowners assume that this is the only cost-effective way of building the structure of a home.

While timber framing with round poles used to be customary in areas where wood was in abundance, transitioning to 2x4s and plywood was a way to vastly limit the amount of wood needed to create a solid and durable house structure. Wood framing of any type is considered to be the most environmentally friendly farming technique as wood has a much lower carbon footprint than steel, concrete, or other building materials.

However, 2x4s and sheets of plywood have seemingly been given a monopoly in the construction industry, when alternatives such as bamboo and cordwood have unique applications for sustainable home construction.

While it is true that 2x4s and plywood allowed homes to use much less wood than other homes (think the old-style log cabins that used entire tree trunks for walls), that does not mean that new homes use small amounts of wood. One estimate finds that a 2,400 square foot home might use 60,000 pounds of wood or 15,000 linear board feet of wood material. In terms of translating board feet into trees, 15,000 linear board feet equates to at least 20 mature pine trees that were 80 feet tall and 2 feet in diameter.

Those pine trees that are milled into 2x4s are most likely pressure treated with several dangerous chemicals. Chromated copper arsenate is one of the most common materials used on pressure-treated lumber. While this chemical does preserve the wood, it also has high toxicity levels and has been related to itching, burning rashes, neurological symptoms, and breathing problems in humans.

Plywood is a composite wood product where the small wood particles are held together by glue or resin. Formaldehyde is one of the most common resins used in plywood. Since formaldehyde is a gas, it can release as a vapor into the home over time. Studies have shown that exposure to formaldehyde is associated with respiratory illnesses, eye, nose, throat irritation, and nasal cancer in several animals.

The health issues and questionable environmental sustainability of 2x4 and plywood stick frame construction are well documented. While you can find non-pressure treated wood and plywood that is formaldehyde-free, there are other ways to frame a home.

guadua bamboo construction
Photo courtesy of Guadua Bamboo

Bamboo

Bamboo is actually a type of perennial grass that people across the world have been using bamboo as a building material for thousands of years. From Nipa huts in the Philippines that resist the monsoon winds and rains to luxurious three-story hotels in Guatemala that are completely framed from bamboo, this building material offers several benefits and advantages.

Are There Advantages of Building With Bamboo?

The primary benefit associated with bamboo is related to its speed of growth. Unlike other tree species that need 30-40 years of growth in order to be harvested for timber, bamboo can grow to extreme heights, sometimes reaching upwards of 85 feet in as little as four years. Because of its fast growth rate, bamboo also creates an enormous amount of biomass and has been shown to be extremely efficient at capturing carbon from the atmosphere. These growth characteristics mean that bamboo can be grown and harvested in a much more sustainable manner than other tree species (such as pine) that are typically used for 2x4 production. Bamboo is considered a “rapidly renewable” material in all of the US Green Building Council’s LEED rating systems.

The benefits of bamboo construction, however, go much beyond their fast growth rate and ability to capture carbon. Some other benefits of bamboo framing include:

  • Bamboo is hollow inside, which makes a lightweight building material—making it less costly to transport over long distances.
  • While the starch in bamboo can attract termites and other insects, it can be preserved naturally through a smoking process that does not rely on any chemical products.
  • The nodes in bamboo (or the dividing lines) give higher tensile strength than even steel. Also, the fibers run axially adding additional strength while also allowing for a certain degree of bending. This makes bamboo an excellent resource for building in earthquake-prone areas.
  • Bamboo is naturally fire-resistant, and it can withstand temperatures up to 4,000 degrees Celsius due to the high amount of silicate acid.

What Are the Challenges of Building With Bamboo?

The biggest challenge that bamboo construction faces is related to securing a steady supply of this wood-like product. While there are species of bamboo that can be grown in cold climates, the best species of bamboo for construction (Guadua bamboo) is a tropical species, and this can present difficulties in importing large quantities of this building material to frame an entire house. It is generally agreed upon that bamboo and nails do not go together because nails tend to split (and thus weaken) bamboo. Finding alternative techniques to secure bamboo is another challenge that this sustainable framing alternative faces.

cordwood construction colorado
Photo courtesy of cordwoodconstruction.org

Cordwood Homes

Cordwood construction (or cordwood masonry) is a natural building technique wherein pieces of "cordwood," or relatively short pieces of debarked trees, are placed crosswise along the wall. These pieces of wood are held together with some masonry mortar, such as cement or earthen materials like cob.

What Are The Advantages of Building With Cordwood?

The most obvious advantage or benefit of cordwood construction is the aesthetically pleasing look of walls incorporating wood of different shapes and sizes. Bottles, glass, and other materials can also be included in the wall construction to create murals and uniquely colored light entries into the home. However, the benefits of cordwood homes go beyond the aesthetic appeal to include some of the following advantages:

  • High thermal efficiency: The mortar used in cordwood construction acts as a thermal mass, meaning it has the ability to gather the heat of the sun during the day and slowly release that heat over the cooler nights. Many builders will incorporate sawdust or other material into the mortar to increase the insulation properties of cordwood.
  • Another benefit of cordwood construction is that it can use the ends of logs and other wood that isn’t useful for other industries. Humans cut down around 15 billion trees each year, and the branches and log ends of those trees are often either burned or left to rot. These “extras” from the forestry and logging industry work perfectly well for cordwood walls.
  • Cordwood walls can be load-bearing or built as infill for a round wood post and beam structure. If you do choose to make cordwood walls load-bearing, this significantly reduces the amount of wood in the construction, and the pieces of cordwood that you do use will largely be low-value wood or byproducts from the milling operations.

Are There Challenges Building With Cordwood?

The biggest challenge to cordwood construction is finding a contractor who knows how to build with this technique. While you can take on a cordwood home as a do-it-yourself project, it is worth mentioning that it will take a lot of labor. Earthwood Building School is one natural building school that offers workshops and classes on how to build with cordwood. Of course, the overall sustainability of building with cordwood will depend on where you live. If you live in a forested area where cordwood is abundantly available and inexpensive, this might be a construction alternative worth exploring.

The Bottom Line

Due to sustainability and health issues associated with the traditional 2x4 / plywood stick frame home, the home building industry can look to bamboo and cordwood construction as more sustainable alternatives.

Disclaimer: This article does not constitute a product endorsement however Rise does reserve the right to recommend relevant products based on the articles content to provide a more comprehensive experience for the reader.Last Modified: 2021-07-09T11:49:43+0000
Tobias Roberts

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.

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