Cob, Straw Bale or Earthbag: Which Is the Best?

Reader Contribution by Atulya K Bingham
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Cob house

I love mud and straw buildings for so many reasons. They are sustainable (unlike log cabins, trees don’t need to be felled), inexpensive and the maintenance is a cinch. Three popular mud and straw-based natural building techniques are cob, straw bale and earthbag. People often ask me which I think is better, or greener. Each has its pros and cons.

Strawbale house

Your climate, the topography of your land, and which materials you have to hand are crucial in choosing which technique to use. Building a straw bale house when there is no straw in your area means squandering fossil fuels to ferry the bales in. On the other hand, earthbag building usually involves polypropylene bags – not exactly bio-degradable. Cob is probably the greenest method, but takes time and not the most practical if you live on a flood plain.

Earthbag house

11 Materials Considerations for Natural Building

So here’s a checklist of 11 points to consider when choosing between straw bale, earthbag and cob.





Difficulty of technique

Cob construction is time-consuming, but fun. Patience and some know-how are necessary.

The interior is completed along with the exterior, so finishing is easy.

Straw bale is the fastest and least labour-intensive of the three. Bales are light compared to sacks filled with mud. You can have a house up in weeks or less. Finishing the interior may take longer.

Earthbag, is labour-intensive compared to straw bale, but the technique is pretty idiot-proof. Earthbag homes can be built fast, depending on the energy of the team. Finishing the interior may take longer.


Mud is free. Labour, time and learning the art is where you could spend money. A great technique if you have volunteers and plenty of time.

Depends if you have bales to hand or not, and on the price of the bales in your area.

The post and beam structure could be more expensive.

The materials are very inexpensive for roundhouses. Mud is free. The sacks are inexpensive. Labour is the key factor for cost here.


Earth has poor insulation.

Great insulation.

Poor insulation.

Thermal mass*

Great thermal mass.

Poor thermal mass.

Great thermal mass.


You can create any shape with cob, that’s the beauty of it.

Squares and rectangles are the most logical choice for straw bale, as the bales are cuboid.

Earthbag definitely thrives on curves and circles.

Resistance to earthquakes

Stronger than brick, as cob is one monolithic unit.

Excellent. Straw bale has been known to survive an 82-ton force on a shake table.

Almost invincible. Exceeded earthquake test limits with no visible damage.

In the wet

How well cob functions in the wet depends on how high your footings, and how wide your eaves. Cob can resist a fair amount of rain and weathering, but is not recommended on flood plains.

Moisture is the enemy of straw bale, but as long as you construct a decent rubble trench foundation, a high stem wall and wide eaves, straw bale can stand the rain.

Performs the best out of the three in the wet. With a gravel foundation and a decent stem wall, earthbag can survive a flood.

In the cold

Earth works very well with passive solar construction (for those in the northern hemisphere that means south facing windows which draw in the sun’s heat which is then absorbed by the earth walls).

Takes a while to heat up.

Excellent. The high insulation factor means it’s easy to heat a straw bale home.

Earth works very well with passive solar construction (for those in the northern hemisphere that means south facing windows which draw in the sun’s heat which is then absorbed by the earth walls).

Takes a while to heat up.






Cob houses have been standing for hundreds of years in the UK.

With large eaves and the correct moisture protection, straw bale is estimated to last a life time, at least.

An earthbag structure with proper foundations is estimated to last at least a century.

Other quirks to note:



Mice can live in the walls of straw bale homes.

Walls can swell and shrink in areas with drastic seasonal moisture/heat changes. This affects window and door frames.

What’s the Difference Between Thermal Mass and Insulation?

Insulation is the ability of the house to slow down heat loss (or cold air loss). Straw insulates. In practical terms, this means you can heat or cool your house quickly and it will retain that temperature. If you are in a building that you only use once a week, say a church or a meeting room, or you live in the arctic, you need a high insulation factor. Straw bale is the way to go.

A building with high thermal mass takes longer to heat or cool, but retains the temperature for hours. Mud buildings (cob and earthbag) have high thermal mass values. But what does this mean? In winter, earth walls slowly absorb heat in the day, and then release it back into the house at night.

In summer, they absorb the cool in the night and release that cool back into the house in the day time. Earth buildings are perfect for hot, dry and Mediterranean climates. They are also work well in temperate climates where people live in the house the majority of the time.

Round vs Square

I may field some criticism from the straw bale and earthbag purists, but in my humble opinion, if you want a round, oval or curved house, then earthbag is the obvious choice. If you want straight lines, then straw bale is for you.

It is true, people have built round straw bale houses, and square earthbag houses. But this takes greater time, requires a higher level of know-how, and utilizes more resources. Straight earthbag walls have to be buttressed. Round straw bale homes need more adjustment and increased plaster. Why make life difficult?

The Bottom Line

Whichever of the three mud and straw natural building techniques you choose, you will have a more comfortable, healthier, greener, better ventilated, and more soulful home, than if you build using the mainstream construction materials of today (Portland cement, foam, fibreglass, plastic, chemical-based paints and plasters). Your home will breathe rather than sweat. And most importantly, you will smile every time you look at it.

Straw bale house photos by Sophie Hunter.

Atulya K. Bingham is an author and natural builder. She lives in Turkey in her beloved earthbag house. She runs The Mud Website which offers plenty of earthbag building information, a window into Atulya’s off-grid life, and sustainable living tips. She is also currently giving away The Mud Earthbag Building PDF. Mud Ball,Atulya’s popular personal story of building her earthbag home, is available from all major online stores. And read all of Atulya’s MOTHER EARTH NEWS posts here.

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