Build an Earthen Garden Bench for (almost) Free

Build an Earthen Garden Bench for (almost) Free 


In the green building world people are building homes with low-cost and natural materials like clay and straw.  When builders get together for workshops they often will create something useful and practical, like a garden bench, which also serves as a teaching tool.  You can do the same thing in your own yard, with family, a few friends, or even by yourself.

If you are interested in natural building creating something small will give you a good idea of time and effort needed. Working with earth is fun and easy, and children will love to play in the mud with you.  So, as summer is almost upon us, take advantage of the warmer weather and create something beautiful you can enjoy for years to come. There is a lot of great information on building with clay on the internet, and several free teaching videos on that can help you learn. A simple search for “earthen bench,”  or “cob bench” will bring many educational sites and how-to clips to view. I will list resources at the end to get you started.


The stunning phoenix bench and oven inspires many when they see it. This bench started out as a small outdoor bread oven, with wooden benches on each side. Earth artist Kiko Denzer used ‘cob’ which is a mix of clay, sand and straw to create this beautiful yet functional bench. At the belly is a clay oven, called a Horno, and used for baking bread, pizzas, cookies, and casseroles too.  The smoke vents through the beak of the bird.   You can create something this ambitious if you want to take the time, but to start I suggest sticking with a simpler project.  There is also a book by Kiko: “Build Your Own Earth  Oven” that teaches how to build the oven, and gives a solid overview of building with cob too.







Designing Your Dream

You can let your imagination fly. When I began my bench I intended to have curved, polished driftwood pieces to serve as arm rests, and a tall back rest that would be shaped like an ocean wave cresting, with sea shells, starfish and stones embedded in it. I sketched a much fancier design than I ended up building.  As you can see my unfinished bench is more like a couch. I could have added the tall wave-shaped back later, and changed the arms if I wanted, but I moved soon after. The beauty of playing with clay is it allows you to add, decorate, or change  your design and you can recycle the leftovers right back to the earth.


I encourage you to make a small clay model first. Build a mini bench, complete with a foundation.  You could use a single cement block, or glue (with clay)  several stones in the lid of a shoe box, then place your base on piece of plywood so you can turn it as you work.  Use dry lawn clippings as the fiber, or finely chop some straw. This miniature will help as you work on the real version, and you won’t stray too far off your design.

An earthen bench that seats two or three people does take work.  I consider it a medium building project, not a beginner’s project, but if you have friends to help it will go much faster.  To get a picture of the process, with many instructional photos, and a complete step-by-step “how-to” follow the design of an HSU student who started her project on campus at the former CCAT house site. She organized the building of this bench in 2005, and provided a complete history of how it evolved. This photo of her unfinished bench shows the foundation materials they used, and gives and idea of her basic design. Link:


Cob Bench under construction at the Campus Center for Appropriate Technology at HSU, 2005. © Jessica Rendon







Getting Started

You will be using four basic materials. Stones or broken concrete for the base. And clay, sand, and chopped straw for the bench. Or you can experiment as I did, and use redwood sawdust, along with shredded paper added to the earth mix.  My recipe was not a true cob formula, but I was working alone, using the bucket method for mixing, and I wanted to experiment. I learned you can combine a wide range of  natural  and alternative materials as long as you keep clay at the core.

Tools and Materials

• Water

• Clay: which is 20% or more of harvested subsoil- clay is sticky

• Sand:  mixed size ‘sharp’ sand is best (beach or play box sand is too round)

Some subsoils are a good mix of sand and clay already.

• A bale of straw ( not hay…hay is food for horses, straw is waste fiber)

• Testing tools- glass jar with lid

• Shovel, rake

• Wheelbarrow

• 5 gallon  plastic buckets-lots of them

•Tarps/billboard vinyl: 6’x8’or larger

• clean water via a hose is best,  and beats hauling water buckets


Useful:  Large paint stem mixer on an electric hand drill, trowels, garden forks, snug ‘water moccasins’, Neoprene diving booties, old sneakers.



About a foot underneath most topsoil is a sandy clay mix. Clay feels greasy and slippery, and can appear gold, red, grey or brown. Take a small handful and roll a ‘snake’ about five inches long. You should be able to bend it around your finger without it breaking easily. If it snaps quickly you have high sand content, and not enough clay.  A perfect mix is 30% clay to 70% sand, but a 20/80 ratio is acceptable too.


The jar test can reveal your sand to clay ratio.  Place a small handful of harvested clay into a quart jar filled three quarters full with water. Close lid and shake very hard for one minute. With a marker make a line where you see the separation of sand at the bottom, then clay next, and water on the top. Shake again very hard, then let sit overnight and compare the lines of clay and sand.  If there is very little clay you will see only a film of orangey color over the sand portion. You will need to add sticky clay to your mix.


Different parts of your property may have more clay, so test a few areas.  Buttercups and horsetail plants grow in clay soil. Also look at the side of a creek bed, or a high road cut, or home construction site. You will see the different  colored layers where the earth is cut away. Ask permission if on private property, and test the soil before doing the work of dragging it home.  You can also purchase large boxes of inexpensive clay at pottery stores to add to your mix. And if you need sharp sand a builder’s supply store like Hensell Materials, in Eureka will have it, or purchase at Eureka Sand & Gravel.   Don’t use all beach sand or play box sand, it is round in shape, and will not lock together to bind the clay well, but using a little won’t hurt.


Clay you have harvested from the ground can be soaked in water, or left to dry.   Fill a drum with clay lumps and add clean water, let soak.  The rocks will drop to the bottom over time. The higher the clay content the harder the lumps will be, and the longer time needed for them to break up. Use rake or sharp stick  to break up, and start the process well before your building day.  Or you can let  the clay dry in the sun, then sift out rocks and any organic debris through a screen, or hardware cloth (metal screen with ¼” or larger size mesh, nailed to a wood frame). To solar dry the clay faster lay a glass sheet or an old window over it.


You can purchase a bale of straw at most feed stores in Humboldt. You want straw,  which is a waste material, not hay. Hay is animal food, and will sprout, rot,  and attract insects if used. Rye, wheat, and rice straw have different strengths, but we don’t have much selection locally.  For use in cob any straw will work fine.

The Location of Your Bench

Next you have to choose a location for your bench.  You can’t move it, of course, so consider the placement carefully. Under a tree, or near a roof overhang offers some protection, and in winter the bench can be covered with a tarp to protect it from driving rains. Do you want to face west for sunsets, east for morning light, towards the ocean,  or your garden? Decide before you dig a trench.
The organically shaped bench shown here with the wooden shed-style roof was built at the entrance to the Lost Valley Eco Village in Oregon. The builders used wood harvested on site, and included display cases, and embedded stones and glass on the backside.  Color pigments were used, and they kept the arms rests narrow. Instead of a permanent overhang you could choose to use a fabric awning, or other temporary protective covering, or make a detachable shade cloth. Visit their site: and explore the photo gallery.

Cob bench with roof at Lost Valley Educational Center in Oregon. © C. Visnesky










An organically shaped seat on a cob bench. © C. Visnesky


Building the Base

One you’ve chosen the location you will need to dig a shallow trench, four to six inches deep, the width and length of the bench.  The trench is filled with stones, gravel, bricks, clay pipe, or broken up concrete often called ‘Urbanite.” You can fill around the larger pieces by pouring small pebbles in to stabilize.  But don’t use sand as it will hold water and wick it to wet the bottom of the bench.  You don’t want a smooth base top; you need the cob to ‘grab’ to the uneven edges.  Yes, you can pay for new materials, but look around first for what you can salvage.  People have used glass and wine bottles, mortared in rows, or broken bricks, concrete blocks, clay pots, crockery and dishes, or crimped soda cans mixed in with concrete. And you can use wet concrete to pour around the stones to stabilize if needed.  Or build a temporary form box inside the trench and pour a concrete base, bedding rocks and bricks or chunky broken sidewalk pieces on top. The finished base should extend five or more inches above ground.

There is an old English saying, “give your house a hat and a good pair of boots” to protect it. The hat is your roof covering, the boots are the raised foundation. From the images you can see the base of the Lost Valley  bench is narrower than the finished shape, the seat area extends out comfortably, so feet can be tucked under.  Some of the benches here look more like couches. As long as the cob doesn’t touch wet ground your design is fine.

The Work Area

Start assembling supplies and building materials close to your bench site. You’ll need a flattish area nearby to lay the tarps for mixing, (grass is preferable to concrete) plus access to water, or a garden hose; and provide shade with a canopy. You’ll be able to work longer on a hot day if you’re more comfortable.

Keep a couple pails of clean water nearby for washing faces and rinsing hands. One helpful clean up trick is line up three or four plastic dishpans, and step into each, successively, to rinse mud off your bare feet or shoes at the end of the day.


Wear old comfortable clothing of course, and have lots of old towels, and soap for washing up. Wear gloves if your skin is sensitive, and protect your skin with sunscreen. Clay can suck the oils from your skin, and make it feel very dry,  so a coating with heavy lotion or Vaseline after each wash-up will help.

Mixing the Cob

The traditional way to mix clay and sand to make cob is to pour the dry sand on a large tarp, add wet clay in soft clumps, and start stomping, this is called the ‘cob dance” and it can be a lot of fun. Add music, and really twist with your feet.  Wear shoes or water moccasins if needed.

The basic formula, by volume, is three parts sand to one part clay, even two to one can work.  If you have a lot of clayey, sandy subsoil already you may not need to add anything. Make some cob test ‘bricks’ let them dry, and check for deep cracks, or easy crumbling.


After mixing with a rake or by foot for a few minutes lift the edge of the tarp to roll the mix into a burrito shape, then stomp again.  Once the clay and sand are well mixed into a heavy cookie dough consistency, the chopped straw is sprinkled on by the handful. The straw needs to be thoroughly combined with the clay.   Straw can be chopped up in a large plastic garbage pail using a weed whacker, or chop with a machete. Pull apart a few inch width of straw from the bale and chop until the pieces six to ten inches long.   Once the straw is mixed in test the strength of the cob by shaping a baseball size lump by hand, and drop it to the ground from chest height. If it breaks apart easily it is too dry. If it flattens out it is too wet. The videos online will give you a good idea of how the cob should look. View this Build it Green! Cob demonstration.  It’s a three minute demo of mixing sand and dry clay, with water and straw added, on a tarp:

If you mix on a tarp realize your thigh muscles will get very tired quickly, and bare feet are tender, small stones or debris  left in the harvested ground clay can hurt. I recommend wearing water moccasins if you have them, or tightly tied old sneakers. The sticky mix can pull the mocs off your feet too.  But it is fun to act like a kid and at least try going barefoot.

You can compare the size of your foot, and the size of the project and see it will take a while to mix cob this way.  Over the centuries oxen or horses were tied to a center post, and the animals mixed the clay with their hooves as they trod in a circle.   You can also try making “cob in a bucket.”  It is a lot slower to create a few hundred pounds of cob but you can sit in the shade and add the materials to a five-gallon pail and use a garden fork, a mixer blade on a hand drill, or your hands to mix.  I’ve even used an electric hand mixer, it works.  Try dumping the mix into a bigger tote bin and add chopped straw and mix with your hands, feet, or with a rake.  Or, try laying a smaller tarp over the wet mix and step on it repeatedly.

An ATV or small tractor can also be used for mixing a large quantity of cob.  By using a concrete driveway or hard-pack dirt area the small vehicle is driven back and forth to mix. With a Bobcat tractor the scraper pushes a large mass of cob into a pile, and drives over it again and again.  A cement mixer has been used also, with success, but be careful of using too much water. It should be doughy, not wet to the touch.


When the cob is mixed to a dense doughy consistency it is hand shaped into rough loaves and pressed onto the base.  Holes are poked into the loaf with your thumbs, or a thick curved branch, or wooden dowel, called a ‘cobber’s thumb.’  A tool spares your thumbs from getting tired. The next loaf  ‘knitted’ with hand pressure into the first so the clay interlocks permanently, and when cob dries it becomes almost as hard as stone. Loaves are continuously added as the shape emerges, going up about six inches at a time, and allowing an hour  or more between layers to allow for dry time   If the mix is too wet the cob will slump or ‘ooge’ outward the higher you go.  You can whack the bump with a baseball bat, or a shovel, to straighten, or carve off  the hump with a machete type blade. Tapering up slightly as you go will help avoid this problem.   Cob can also be left covered, then lightly watered,  before continuing to build. If you skip a week of building just hose down the dry areas to moisten, and continue adding cob.


 Schoolyard Dragon made of cob with an embedded stone seat







Cob Dragon curled on a stone and brick bench. 

Be Creative, Go Wild!

You may think you can complete the shape of the bench in one weekend, but don’t count on it.  Just building the base will take time.  Allow a month or two from design to the final touches. And don’t rush, enjoy the process.  This is the fun part. You will get new ideas as you go along.  And a bench doesn’t have to look like a place to sit; many designs built at schools are shaped like animals, dragons, and mythical creatures. One long sculpted alligator bench I saw had a flat top, for seating, that was decorated with small ceramic tiles. Many benches do not have armrests, or use other materials, such as the driftwood I suggested.  You can include ‘found’ materials such as wagon wheels, or sculpt animal or zodiac shapes to include in the design.  Often human faces, children’s handprints, and small creatures are included.  One cob entryway had a sculpted sleeping panther ‘draped’ over the wood door frame. Glass beads, seashells, coins, mirrors, teacups, or tiles are added, and blue glass bottles are embedded through the thickness of the cob to let light shine through.   Arranging the bottles in flower shapes or as geometric, or free flowing design creates a unique pattern.  A friend used a cob mix four inches thick, on the front of her straw bale barn wall and shaped a life size horse, and placed a row of large sunflowers, and waddling geese, in relief, on the other walls.

The bench shown here at Emerald Earth community has a large lizard sculpted on the back of the bench. And you’ll notice this cob bench has seating in both directions so people can enjoy the pond view, or the garden view.  The green child’s couch at Emerald Earth has a final polished coating that protects the cob underneath.  This highly compressed lime plaster coat is tinted with various pigments. The final plaster coat of cob uses finely chopped straw, and finer sand. This creates the smooth, more impervious protective coat. The ‘fuzzy bear’ look  slowly disappears. Most earthen benches are left their natural clay color, or can be pigmented in the final coating, or painted on, in a water or lime mix.  The bench is never covered with a latex, or oil paint, the cob needs to be left to ‘breathe’ and let moisture wick away naturally.

Extended cob bench with two-way seating and large sculpted lizard. © C. Visnesky










A garden bench left completely exposed to driving rains will begin to return to the earth. But after all your hard work proving some level of protection is advised.  After all, houses made of cob in England and Wales have endured for hundreds of years through extremely harsh winters because they were maintained and repaired each spring.

You can see some erosion on the seats and backs of a few of these benches. A fresh cob mix is made, the  damaged area wetted, and the new cob is added, and smoothed over.  Yet another benefit of using natural materials…they are repairable.


 Small, green, cob bench for children has a colorful protective coat of lime. © C. Visnesky


 Cob seating with an earth oven connected for baking at Emerald Earth Sanctuary. © C. Visnesky


More Information

You can search the web and easily find many good informational sites. Start with Kiko’s earth oven article:

Then visit and search for “building with cob, earthen bench, etc.

Visit the sanctuary site, located in Mendocino County, CA.

Becky Bee produced one of the first books on building with cob, and it is now offered online for free to read:

Cob Cottage Company in Cottage Grove Oregon offers cob classes, as does Barefoot Builder, in Tennessee. Plus there are many ‘natural building’ websites where dedicated people share their creativity.  Explore the Natural Building Network for a nationwide list of workshops and events:

There are also several DVDs and books on building with clay, cob and earth., but from your local independent book seller.

 Get a view of the finished CCAT cob bench here: Repairing Plaster of CCAT’S cob installation: (poor sound quality, 3.38 min.)

Emerald contributor since March 2012


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