You’ve likely heard of the tiny house movement, but have you heard of a cob house?
This is a sustainable way of living that’s trending again.
People love its minimalistic, inexpensive, and organic style.
In this blog, we’ll talk about everything you need to know – from what a cob house is to how to build a cob house yourself.
Let’s get started.
1. What is cob?
Cob is a natural building material made from subsoil, water, fibrous organic material (typically straw), and sometimes lime.
The contents of subsoil naturally varies, and if it doesn’t contain the right mixture, then it can be modified with sand or clay, so it is the right consistency.
In short, cob is essentially clay, sand, and (usually) straw mixed together to be used as a building material.
In some ways, it is similar to bricks, but it is also advantageous to the builder because most of the building materials are available on any given site, or they can be purchased easily and cheaply.
2. Why build a cob house?
A cob house is essentially a mud castle, but for adults.
It’s a building technique that has been used for the last 10,000 years.
Its natural and beneficial building properties lend themselves to a comfortable home.
In the next section, we’ll discuss why a cob house is so beneficial.
3. What are the benefits of a cob house?
Cob houses have a lot of thermal regulation
Cob houses have thick walls, which means they regulate their temperature well.
In the heat of the summer, the walls keep the interior of your cob house nice and cool.
You’ll stay warm even late into the night.
Cob houses last a long time
Cob construction is incredibly durable and won’t begin to weather for years.
A good roof protects your cob house from the elements.
If you do notice the exterior of your house wearing down, you can always re-apply a new layer of cob to make it as good as new!
Cob houses are affordable
Cob is made out of inexpensive materials, and it can be acquired in large quantities.
While you’ll need to do a soil test to see if it’s suitable for cob building, most sites have usable soil.
This makes it cheap and easy to build.
Cob houses are fairly fire-resistant
Unlike houses built from wood, cob houses are primarily clay and sand.
This means there isn’t much that can be burned up.
As a result, cob houses are popular in areas that are prone to wildfires and other extreme weather.
Cob houses are healthy
Cob houses are great for air quality.
The only thing you’ll need to pay special attention to is moisture.
It can take months to years for your cob to dry out fully.
The bulk of the moisture will dry out in the first year, but it will not fully cure for 1-2 years beyond that.
Once you’ve built your cob house and added your roof, allow it to breathe for several months before moving in.
Then, you’ll need to do an internal sealing process.
After that, you’ll need a dehumidifier in the home to reduce the amount of moisture that is in the air.
This is an extensive process, but it will improve the damp quality of the air that is in the home.
Cob houses are organic and stylish
Of course, this is a matter of personal preference, but it’s another reason why they’re popular.
Cob houses have a unique style and curve to their walls.
They look like hand-sculpted houses.
They’re cozy, appealing, and comforting.
If you love the idea of living somewhere that is natural and organic, then this is the home for you.
Cob houses are durable and earthquake resistant
Cob is an extremely durable base material, and the whole structure acts as one monolithic piece.
Thus, even during earthquakes, it doesn’t develop cracks.
Cob houses are insulated for sound
Cob houses are among the best for sound insulation.
The walls are made from an organic material that has great sound-absorbing properties that keep external noise subdued.
4. How long does cob last?
The oldest cob house currently standing is 10,00 years old.
If this doesn’t speak to how strong and durable cob houses are, then nothing will.
Cob houses are built to stand forever as long as their roofs are maintained, and they are properly looked after.
5. How do you make cob?
The mixture of cob itself is great – the most sustainable building substance there is!
But you must get the mix right.
Here’s how you can make cob.
Mix roughly 2 parts clay with 1 part sand, sprinkling with straw and a little bit of water.
The best way to mix these two together is with (surprise!) your bare feet.
You want the ingredients to be well mixed and moist.
The mix should hold its form solidly and not look like it’s melting or slumping.
The straw should also be worked in well.
Make a test brick and allow it to dry before starting on your cob house.
6. How do I prepare to build a cob house?
Are you sold on cob and ready to build a cob house yourself?
Cob is easy to learn and requires no special equipment.
There are just a few steps you should take to prepare to build with cob in your community.
Check with your local government
You need to check with your local municipality to see if it’s possible to build a cob house in your area.
Some communities don’t allow off-grid homes (some areas define this as off the electrical grid while others define it as a non-traditional structure).
If you live in a rural area, you’re more likely to be given the okay.
Choose land and draw up plans
If you’re going to build a cob house, you’ll need a plot of land with a relatively flat spot.
Then you’ll need to draw the plan.
Generally, cob lends itself well to organic shapes.
You can use curves, bumps, and flowing lines because lumber isn’t involved.
Roofs can be constructed the same way.
Just make sure you keep your climate in mind!
Prep the building site
Once you have a plan, walk your proposed site.
If there are dips that need to be filled in or hills that need to be moved?
If so, you’ll want to take care of these before you start building.
You’ll also want to go over the land with a roller to ensure you don’t have soft areas that will sink in later.
7. Why is cob popular?
Did you know cob is currently trending?
Price of course!
If you live in an area with plenty of natural resources, cob is a cost-effective way to build a house.
8. What are the characteristics of cob homes?
Here are common characteristics of cob houses.
If you love homes that align with these concepts, then cob just may be for you!
Cob houses are typically small and size efficient.
You’re unlikely to come across any cob mansions.
Most natural builders and residents know that cob homes are meant to be simple and down to earth.
If you’re okay with the minimalist way of life, then try out a cob house!
Cob falls under the “natural building” umbrella, and as a result, the natural resources for this project can be found in your local area.
A cob house can be built from the earth right beneath the building site, and whatever other natural resources that are needed (sand, gravel, stone, timber, etc.) can be sourced locally as well.
Often, people are drawn to cob houses because they are beautiful and have creative designs.
Because builders do not have to limit their creativity to 90-degree angles, they have much more freedom to create.
They can build whatever comes to their imagination.
Everything used to make cob is a natural resource.
You can feel confident that you’re choosing materials that are healthy for the Earth and you/your loved ones!
Building a cob home can help bring your community together.
It is a good social activity as everyone bands together to help – even children can participate!
Cob houses actually meet high standards.
While they may appear primitive, cob homes do need to comply with all local building codes.
In addition, cob does not negatively impact the health of those living in the home or the Earth itself.
Because cob houses are thermal masses that absorb sunlight, they’re warm during the night and cool during the day.
As noted, everything you need to build a cob home is already available where you are.
Other parts like windows and doors can be salvaged or purchased.
You can build a high-quality cob home for as little as a few thousand dollars.
If you’re looking to stay debt and mortgage-free, consider a cob house!
Traditional homes are built with synthetic and industrial materials.
On the other hand, cob homes are built entirely with natural and clean materials.
As a result, they “breath” through the tiny pores that exist in the material, and keep the air inside fresh and clean.
If you suffer from indoor allergies, then you could significantly improve your quality of life by eliminating the toxins in your home.
As noted above, cob homes are strong and resistant to earthquakes.
They can last for thousands of years as long as they’re maintained correctly (and this is fairly minimal upkeep).
If you build your family a cob home, it will last for generations to come.
With noise-absorbing properties, you’ll never have to worry about exterior noises penetrating your cob house or noise generated in your cob house going anywhere.
You can feel confident that your house is nice and private.
9. How do you build a cob house?
Here are the steps to building a cob house:
Prepare your building site
You can’t just decide to build a cob house and get started right away.
Read #6 to learn more about this process.
Pour a foundation
You’ll need a foundation for your cob house.
You can either use a more traditional poured concrete foundation, or you can form a cob floor.
Cob is highly durable once it’s dried, and it can be walked on repeatedly without damage.
You can sprinkle sand on top of it and seal it to make it non-skid, or you can paint it to make it a different color.
Just make sure you wait until your foundation is completely dry before you walk on it.
This will help avoid damage!
Mix the cob
It’s time to start mixing the cob for your walls.
See #5 for information on how to mix cob.
Build the walls
Once you have your cob mixed, you can use it to form your walls.
To make walls, you should form lumps with the cob and add a handful at a time, smoothing it out as you go.
Avoid “slapping on” the cob as this will draw moisture out of the walls, and you want it to cure naturally.
As you work, do your best to keep the walls straight.
You do not want them to become thinner at the top and take on a pyramid shape.
As you add new layers, poke holes into the top.
Then, when the next layer is added, sink the bottom of it into the holes for more stability.
You may also consider adding rebar or bamboo poles if it’s a smaller structure.
If you’re incorporating electricity into your cob house, lay out a metal conduit where you want it and work it into the walls as you go.
The same can be done with plumbing.
You can work on cobs for months before you are done.
Try doing about a foot a day.
Unlike concrete, you can add wet cob on top of dried cob.
Form your doors and windows
For the door, you want to form your doorway with a door frame and build the cob around it to secure it.
You can sink 2x4s right into the cob.
The cob won’t destroy the wood.
They’ll both dry out and be fine.
The windows are similar.
Sink 2x4s right into the cob and build a window frame wound it.
Add the finishing touches
Once you’ve got the basics done, you should be sure to add a tin roof, tarp, mud, or even solar panels.
It’s up to you!
You can paint the outside and add all the finishing touches.
10. What else can cob be used for?
Cob is the perfect multi-purpose building material.
In fact, if you’d normally use it to build something in a house, then you can also build it out of cob.
To give you a few other ideas, here’s what else cob can be used for:
If you can make it out of other building materials, odds are you can make it out of cob!
Think barns, well houses, outbuildings, animal pens, storage buildings, etc.
Cob pizza ovens are especially popular because they have consistent heat with some moisture to them.
Unlike traditional home ovens which often have wild heat swings, cob ovens can get up to 800 degrees and make pizza, bread, chicken, roast beef, you name it!
Rocket mass heaters
A rocket mass heater is a high-efficiency space heating system where the heat is piped through a large mass of cob (and sometimes rocks).
In this heater, the cob will heat up and transfer this heat to the interior of the house, which means the larger the mass of cob, the better.
Often, it will be constructed as a cob bench, so there is a large mass that promotes heating.
Are you inspired to build your own cob house?
This way of living has existed for thousands of years, and it’s no wonder why!
It’s simple yet inexpensive and effective.
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Disclaimer: we are not lawyers, accountants or financial advisors and the information in this article is for informational purposes only. This article is based on our own research and experience and we do our best to keep it accurate and up-to-date, but it may contain errors. Please be sure to consult a legal or financial professional before making any investment decisions.