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Mud Magic: Where Cob Wins.
Live Beautifully.
No.063 — Read old posts on Tinyfarmlab.com
Reading Time 4 minutes
When it comes to natural building techniques there are several options available:
rammed earth, adobe, wattle and daub, earthbag, cob, and so on.
Every building technique is suited to some circumstances but poorly to others.
Let’s discuss where Cob Building wins and where you have to use it with caution.
Where Cob Wins:
1) Cob Insulates from Temperature Change:
Heat flows through the Cob at 1 inch per hour( Rule of Thumb). A two-foot thick wall takes about twenty-four hours to transmit the effect of heat or cold all the way through.
In dry, hot climates, cob walls absorb heat during the day and release it at night, naturally regulating indoor temperatures.
You would need good ventilation to replace the released heat by the cooler air.
It’s a great choice for sunny days with cold climates.
2) Cob is used for Passive Solar Buildings:
Cob provides much better insulation than rock, brick, or concrete.
Cob floors, benches, walls, and natural plasters store heat like thermal batteries.
Our dear friends building with cob.
3) Cob is ideal for building organic shapes
Curved, thick walls make a space feel larger than straight, boxy ones of the same size.
Spaces can be designed to fit specific needs, creating cozy, personalized environments.
Curved buildings need less space, requiring less energy for heating and cooling, less maintenance, and fewer materials.
Cob encourages site respect. Slow and deliberate process forces builders to pay attention to their site. Buildings respond better to the site's aesthetics, ecology, and microclimate.
4) Cob is easier to learn
Cob is simple to learn with practice.
It does not need mechanical tools or power equipment on site.
Cob is safe for inexperienced builders. It’s idiot-proof.
There’s not much that can go dangerously wrong;
almost everything is reversible.No material goes to waste.
5) Cob insulates from sound
Cob is an excellent sound insulator, effectively blocking outdoor noise from highways, railways, airports, and factories due to its poor sound transmission properties.
It can also keep noise in, for example from a machine shop or music studio.
6) Cob Works Where Other Earthen Techniques Don't:
Cob works in cool, damp regions where other earthen methods like adobe are unsuitable due to moisture absorption.
Cob can be a good alternative to rammed earth when machinery is costly or difficult to work with.
It’s a good choice where wattle is scarce.
Cob is ideal for remote sites where importing materials is difficult or where lumber and processed building materials are expensive.
7) Cob is democratic
Cob fits anyone’s strength, making construction accessible to women, children, the elderly, and the frail.
There is no heavy lifting. You can use any size of unit, any weight of loaf to build with.
A mix can be any amount of material that you can roll.
8) Cob is wind and fire-resistant
Cob buildings with earthen roofs are ideal for areas prone to forest fires.
Heavyweight earthen roofs locked securely in thick cob walls work well for areas where tornados and cyclones are frequent.
9) Cob is durable
Well-maintained cob buildings have stood for centuries, often without needing major repairs.
In England, there are tens of thousands of cob homes, many of which have been in use for over five centuries.
Where you have to use cob with caution:
1) In cold climates on north slopes:
In cold, dark climates, on north-facing slopes, or in areas with little winter sun, cob's high thermal mass can trap cold, making it harder to maintain warmth indoors.
More energy will be needed to heat an all-cob building than one with more insulative walls.
In these cases, cob can be used for walls, floors, and benches with strawbale insulation outside.
2) In Flood plains:
Cob walls are highly resilient to normal moisture and weather, but prolonged or repeated soaking is the biggest threat to their stability.
Avoid building cob structures in flood plains, seasonal creeks, gullies, or below the high storm-tide line at the seashore, as they are vulnerable to water damage.
We hope this information helps you make a sound choice while building naturally depending on your geography and climate.
In case you need any further help, please write us an email.
Love,
Raghav and Ansh
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What you can watch - Cob is the ultimate material!
What you can listen to - Earth to Shelter: A Masterclass on the Science of Mud Buildings with Yask Kulshreshtha
What You Can Read - A case study of cob earth-based building technique in Matagalpa, Nicaragua – LCA perspective and rate of adoption
This is a great study for the life cycle assessment of cob buildings and understanding their properties.
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