History of Cob Building

How to build with cob - An introductory page on cob basics

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Ancient History of Cob

No one knows exactly when cob originated, but presumably it came about when mankind started building permanent structures and settling into cities. Cob is one of the simplest ways of building one's house out of natural materials, along with:

• adobe
• sod
• rammed earth
• straw-clay
• wattle-and-daub

All of these building styles exist in cultures at the same level of technological progress, and one often evolves out of another. There is evidence from around 10,000 years ago that people living the region of Jericho had buildings made of adobe, which suggests that cob could have also been present around or before that time.

Adobe bricks are a further refinement of the cob process in that the whole structure can be made before assembling, instead of having to wait long periods of time for each layer of the cob to dry, but lose some structural stability and creative shapes. However, there is no definitive evidence of a cob influenced culture besides England.

Cob's History in England
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Cob enjoyed much popularity in England, but the origin of its use there is also unknown. However, we do know that cob construction has been used since the 1200's. Cob was used from the 13th century up until the early 20th century. However, cob's heyday was between the 15th century and the early 19th century. Cob was one of the primary methods used in building construction for all social classes up until the early 1800's, when industrialization allowed fired bricks to become readily available for the richer classes.

Cob was most popular in Southwestern Britain and Wales because of the local materials; wood is more scarce and the soil is a sandy clay, the perfect type to use in cob. Many cob houses built in Devon County in this era are still standing today.

Fig. 2- A cob house built in Devon county, England, 1539. Source: www.cobcottage.com

The old style process:

1. Clay, sand and natural fiber are mixed
2. The building's foundation is laid out so the walls would be between 20 to 36 inches wide
3. Layers called "lifts" are applied- The lifts would be somewhere between 6 inches and 3 feet depending on the application and the conditions.
4. Allow time to dry- Before applying the next lift, the previous one had to dry which took up to several weeks

For the most part, cob buildings from this time were built cooperatively, especially in small poorer farming communities where all the workers would join together to build a house. However, it would take an entire dry season for the group to complete one house. But, once completed, cob houses needed no significant upkeep or repairs for up to a hundred years.

Cob's Expansion around the Globe
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When the British Empire stretched across the globe, English settlers brought their own technologies and methods to the new lands. And, of course, they brought their knowledge of cob building too.

New Zealand: The local grasses and sticky clay soil facilitated building with cob here. The settlers built entire towns with cob, constructing at least eight thousand cob buildings in New Zealand. A few hundred of those buildings still survive.

Australia: The settlers of Australia favored rammed earth and mud brick building techniques because of the different soil type than in New Zealand, but some cob structures still exist in Western and South-Western Australia.

North America: Cob was not nearly as popular in North America compared to other places colonized by the British. The reason for this is the surplus of timber and the necessity of speedily built buildings before the onset of cold winters. Also, the rapid expansion of the settlements along the East coast hindered building strong cooperative communities to build the cob houses. Therefore the cob buildings in this region that survive to this day are very scarce.

The Modern Cob Renaissance
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Fig. 3- An example of a modern cob house in Devon County. Source: www.cobcottage.com

The period of industrialization and expansion caused people to associate cob houses with

simple or primitive people. However, during the 20th century, attitudes of appreciation came back into the public mind. After seeing enough brick buildings, thatched-roof cob cottages were appealing as quaint and charming.

The problem was that many of the original builders had passed away in the long absence of cob construction, but somehow enough of the lore and traditional methods had survived to allow a comeback.

The only significant differences between the modern "traditional" method and the original traditional method is that a tractor is used to mix the ingredients (instead of horses or oxen) and, in some cases, more sand or shillet (crushed rock) is added to strengthen the mix.

1978- The first Modern-Age cob structure is built, a bus stop shelter created by Alfred Howard, a devoted cob restorationist.

1994- Cob builder Kevin McCabe constructs the first modern "ground up" cob house

1989- Oregon cob is developed and interest in cob begins in the U.S.

"Oregon Cob" is Developed
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Fig 4. The interior of an Oregon Cob house, built in 1995. Source www.cobcottage.com

In 1989, Ianto Evans and Linda Smiley founded the Cob Cottage Company in Western Oregon. Ianto, growing up in Wales, was familiar with this unusual building practice, and wanted to recreate a cob house on his own. However, since he and Linda Smiley could not find anyone who knew the actual historic process, they experimented on their own and developed a different method which became to be known as "Oregon Cob"

Oregon Cob differs from original cob in several ways:

• Quality ingredients are used: instead of simply soil, separate clay and sand are mixed together
• The ratio between clay and sand is important and specific
• Wet bricks called "loaves" (or "cobs") are used instead of lifts

All of those characteristics cause the buildings to have slightly different properties than the original cob. For instance, walls can be built thinner, only 12-20 inches thick instead of 20-36 inches while still retaining their structural stability. Also, the addition of long, higher tensile fibers allow for more curvatures and arches than traditional buildings. An example of the sculptabilitiy of Oregon Cob is shown in Figure 4.

References:

Pictures reproduced with explicit permission by Cob Cottage Company- http://www.cobcottage.com/

This page created by Jeffrey Steuben. Spring 2005. jls125@humboldt.edu

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