{"id":1576,"date":"2025-07-24T10:00:23","date_gmt":"2025-07-24T10:00:23","guid":{"rendered":"http:\/\/www.angesfinanciers.org\/?p=1576"},"modified":"2025-08-01T15:11:05","modified_gmt":"2025-08-01T15:11:05","slug":"how-to-make-cob-a-mainstream-building-material","status":"publish","type":"post","link":"http:\/\/www.angesfinanciers.org\/index.php\/2025\/07\/24\/how-to-make-cob-a-mainstream-building-material\/","title":{"rendered":"How to make cob a mainstream building material"},"content":{"rendered":"
\"CobBauge<\/div>\n

Despite its huge environmental benefits, cob<\/a> is an extremely niche construction material<\/a>. As part of our Building with Cob<\/a> series, architecture editor Lizzie Crook<\/a> explores what it would take to change that.<\/span><\/p>\n

“Cob really is the perfect regenerative material,” said architect Alice Hardy of building charity Global Generation<\/a>.<\/p>\n

“Its excellent environmental credentials come from its ability to be sourced locally to a site, the fact that it can be recycled and used again and again, and that it can last an exceptionally long time.”<\/p>\n

According to cob-brick innovator Tavs Jorgensen<\/a>, cob “has all the advantages that you would want in a building material”.<\/p>\n

“Cob building is a method we’ve forgotten to use, and it has an enormous potential in terms of low-carbon construction,” he told Dezeen.<\/p>\n

“As long as there’s clay, sand and fibre, then cob buildings can be done and should be done.”<\/p>\n

Waste earth “there for the having”<\/strong><\/p>\n

Used for millennia, cob is a type of unfired earth-based construction material made from clay-rich earth, specifically subsoil, mixed with fibrous material such as straw and water. Sometimes, sand or aggregate is added to give greater compressive strength.<\/p>\n

It fell out of use with the rise of mass-produced fired bricks during the Industrial Revolution. But there is a renewed interest in cob today because of its material makeup, which means it is low-carbon, non-toxic and ubiquitous, as well as compostable and reusable.<\/p>\n

Cob is also celebrated for its thermal mass and moisture-regulating properties, which can help create comfortable interior environments \u2013 a quality many conventional construction materials, including fired brick, do not offer.<\/p>\n

Plus, a cheap, highly sustainable source of cob’s main ingredient is readily available in the form of waste earth from construction sites, the vast majority of which currently goes to landfill.<\/p>\n

“We should be banking this earth for future construction, because, excuse the pun, it’s dirt cheap \u2013 it’s there for the having,” said architect Anthony Hudson<\/a>.<\/p>\n

\"CobBauge
Hudson Architects create a house using CobBauge. Photo by Joakin Bor\u00e9n<\/figcaption><\/figure>\n

For these reasons, its proponents believe cob should be reintroduced as a sustainable alternative to concrete, breezeblocks and fired bricks in construction, particularly in house-building.<\/p>\n

But despite the benefits, only a tiny number of modern cob buildings have been constructed. So what’s holding the industry back?<\/p>\n

“Cob’s big problem has always been that it hasn’t got huge insulation value,” said Hudson.<\/p>\n

“To meet current building regulations, you’d have to build a house with walls 1.5 metres wide, if it were just cob.”<\/p>\n

To address this issue, an international team including researchers at the University of Plymouth developed CobBauge<\/a> \u2013 a contemporary version of traditional cob.<\/p>\n

CobBauge is a composite wall system that is made of two grades of cob bonded together. A dense version is used for the outer wall, and a more lightweight version for insulation.<\/p>\n

Further innovation needed<\/strong><\/p>\n

It also helps overcome another problem with traditional cob: it can be slow to build with, which means the cost of labour is high.<\/p>\n

CobBauge utilises a mesh formwork that helps speed up the dry time \u2013 approximately a week and a half \u2013 before the mesh is raised and reused for further layers.<\/p>\n

However, even CobBauge is not well-suited to the commercialised and fast-paced construction industry to which we have become accustomed, largely because of its seasonality.<\/p>\n

“You can start earliest in late February and go on to October,” Hudson explained. “It gets to then and you’ve got too much humidity, so cob never dries out, and you can’t build on top of it because it would just collapse.”<\/p>\n

Therefore, some proponents think further innovation is needed to facilitate a cob comeback.<\/p>\n

Researchers are now turning their focus to standardisation and prefabrication, including the CobBauge team, which is also looking into flying factories and utilising automation.<\/p>\n

\"Extruded
Tavs Jorgensen is developing cob bricks. Photo courtesy of CFPR<\/figcaption><\/figure>\n

Another example of standardisation of cob is Jongesen’s extruded bricks<\/a>, and Strocks \u2013 a type of cob-based brick by HG Matthews, which makes the material accessible.<\/p>\n

“We’re making great progress in terms of what we’ve achieved so far, but there are still some challenges left to address to make a production at an industrial kind of output level, but it absolutely can be done,” said Jorgensen.<\/p>\n

“It’s a question of us investing in the research and development of using it on a mass level.”<\/p>\n

Global Generation’s architect Hardy, who is currently building a cob classroom in King’s Cross<\/a>, believes these kinds of innovations could eventually lend themselves to a hybrid system.<\/p>\n

“I can imagine a panelised prefabricated cob system being used in which panels are prefabricated in timber panels that are delivered and used on site,” she said.<\/p>\n

Regulatory frameworks need to “catch up”<\/strong><\/p>\n

Projects such as CobBauge also aim to address a major hurdle for traditional cob: it is non-compliant with current building regulations in England, largely over concerns about its strength and durability, as well as the insulation challenges.<\/p>\n

Tom Morton, a founding member of charity Earth Building UK and Ireland<\/a> (EBUKI), is confident that traditional cob is safe and viable.<\/p>\n

He believes building regulations \u2013 written for materials that are fired or chemically bound, such as bricks and concrete \u2013 require updating.<\/p>\n

“Like others in the family of nature-based and bio-composite materials, we are all waiting for the regulatory frameworks and financial incentives to catch up with the climate and nature emergency and create the sector environment where we can invest in scale change,” said Morton.<\/p>\n

“It is all possible, but we are still currently at the stage of relying on a limited pool of experts, rather than having mainstream pathways to compliance. It’s a question of scaling up.”<\/p>\n

CobBauge House<\/a>, the first home built using the material, completed in Norfolk in 2023, had a “straightforward” passage through planning and building control and even obtained a mortgage, according to Hudson, its architect.<\/p>\n