Mud for the People! Building an Adobe Garden Wall

This weekend Kelly and I had our first adobe encounter. We were lucky to have been invited to attend a workshop led by Kurt Gardella and Ben Loescher. Kurt also teaches both live and online classes that you can find out about on his website, www.kurtgardella.com. We’ll post announcements for future classes, because I haven’t had so much fun in a long time! This past weekend’s workshop focused on making bricks and building an adobe garden wall. If you want to learn about adobe, Kurt and Ben are the folks to go to. And, lest we forget, adobe is the traditional building material of the Southwest United States and many other parts of the world. Adobe needs just people power and locally available materials.

What follows, after the jump, is a pictorial essay of our adobe experience.

We missed the first day of the workshop, but pieced together what Kurt and Ben went over. One of the first steps is to determine the clay/sand content of your soil and to do that you do a jar test. When you mix some soil with water in a jar and let it sit, the clay settles on top, the silt below that, and the sand on bottom. You can measure the sample and determine percentages.

At the workshop, held in the high desert town of Landers, CA the sand and clay were sourced locally and from the site.

The clay got sifted through 1/4 inch hardware cloth to get out chunky bits that can lead to weaknesses in the bricks.

To make both the bricks and the mortar, water is mixed with a half a coffee cup of asphalt. The asphalt helps the bricks and mortar resist water. Traditionally, prickly pear cactus soaked in water and fermented was used before the modern convenience of asphalt.

Our instructors went with a mixture of about one part clay to two parts sand for the bricks and mortar. 

A couple of handfuls of straw were added to each wheelbarrow full of mortar and brick mix to add strength.

Here’s the consistency of the mortar.

To make a brick you press the clay/sand/straw/water/asphalt mix into a form made out of 2 x 4 lumber. The nice thing about adobe bricks is that you can custom size them for your project, though there are traditional sizes.

Before you build anything, however, you have to test your bricks. Here you can see different sand/clay mixtures drying in the sun. You can also make a brick out of whatever soil you have on hand and see how it holds up.

The first test Kurt did was drop one on a corner from about waist high. It didn’t break and thus passed the test.

Another test is standing on a brick. Even though the brick we used weren’t really finished drying, they still passed. For a building that will be inspected you will probably have to send bricks to an engineer for more precise tests.

This is the way you stack bricks for drying. Depending on the climate, it may take several weeks before they are ready to use.

And you have to be careful how you transport them. This is the right way to stack bricks when moving them in a truck. If you stack them flat you risk a lot of broken adobe. 

Adobe bricks are heavy. To move them out of the truck we formed a big bucket brigade. Here Kurt demonstrates an advanced technique where you toss a brick to the adobe worker next to you.

Ben explained different types of foundations and how adobe construction can meet even California’s stringent building code. And, yes, if you build it right (vertical rebar and a bunch of other details) an adobe building will stand up well in an earthquake.

To begin our garden wall we placed a “story pole” on each end of the wall to keep everything plumb and on the level.

Since it was just a garden wall and not a building, we did a simple gravel foundation beginning with this trench.

And some gravel-compacting line dancing.

Kurt dry-laid the bricks to emphasize that you should size structures to the dimensions of your bricks to avoid, as much as possible, cutting bricks.

When laying bricks we used our thumbs as a guide to space the mortar joints.

Kurt showed a couple of different ways of cutting adobe. One way was just scoring with a machete.

A light tap and the brick broke neatly in two. This brick is still a little moist in the center–good enough for a garden wall, but not dry enough for a building.

Next, Kurt showed how to shovel the mortar (again, made out of the exact same sand/clay/water/straw/asphalt mixture as the bricks and in the same proportions).

After you dump the mortar, you roughen it a bit with the end of a shovel to make it easier to press the brick into the mortar bed.

Here Kurt presses a brick into the mortar and lines it up with the line attached to the story poles

He also checks with a torpedo level. Kurt explained that you can’t “develop a close personal relationship with each brick.” That is, you have to keep the wall level as a whole unit and not get caught up in overusing the level on each brick. He also explained the work flow. The master mason sets the level of the end bricks and the apprentices fill in the center of the wall. When everyone knows their task, with the master providing guidance, things move along smoothly.

This spoon-like object is what you use for “pointing” or creating the groove in the mortar between adobe bricks.

You can also use a bent piece of plastic electrical tubing as a pointing tool. You only point if the wall will not be plastered. If you plaster, irregularities in the joints help the first layer of plaster adhere.

With a lot of people working, the wall went up fast.

Kurt demonstrates an alternate way of keeping the wall plumb and level.

He also showed how you would integrate doors and windows into and adobe structure.

Nearing completion, the wall is looking so good that I want to rush home and build one myself.

Kurt brought along an assortment of tools that you would use for plastering, including some really nice Japanese trowels. He also explained, that for the first plaster coat, you can also just use your hands. Such is the sculptural quality and plasticity of adobe. You never stucco adobe. Adobe is plastered with adobe and/or lime/adobe mixtures. Typically, plastering is done in three coats, a rough coat, a leveling coat and a finish coat. Screen your materials with progressively finer screens as you go. The materials for the finish coat should be quite fine, say fine enough to pass through 1/8″ screen.

We ran out of bricks and did not complete the wall. It also began to wobble a bit, a sign that it’s time to stop. Four or five courses for a structure is good for a day. Let it dry and it will be ready to continue the next day.

At the end of the workshop we went into a little “homesteader’s” cabin on the property. The deal with homesteader cabins is that back in the 1950s that the government would give you a five acre parcel if you built a shack with the minimum dimensions of 12 by 16 feet. So people built tiny shacks to just those dimensions!

Kurt teared off some nasty wood paneling in the shack to show how you could retrofit a building with adobe. Here he is starting to fill the space between the interior studs with adobe. The idea is that the adobe will insulate the walls, providing vital insulation in a harsh desert climate. This may not work as well in more humid places. Here the thick layer of mud will dry fairly quickly. Elsewhere it might encourage mold.

Next we nailed some reed fencing material over the adobe-filled studs and started to plaster the wall with the same adobe we used to fill the wall. The reed fencing gives the adobe something to hold on to. Here again, as with the garden wall, the interior wall would be given three progressively smoother coats.

The miracle of all of this is that it is dirt. The insulation is dirt, the bricks are dirt, the mortar is dirt and the plaster coats are dirt. Nothing could be simpler. There’s an art to it, to be sure, but its amazingly elegant in its essence.

As the sun set over the high desert landscape we concluded our building and headed over to Pappy and Harriet’s for some beer and BBQ. I’m really looking forward to working with adobe again someday soon.

Shameless Self Promotion, With Kitten

We’ve heard from several people that Making It is an excellent sleep aid.

Just a reminder that our two books, Making It: Radical Home Ec for a Post-Consumer World and The Urban Homestead make great holiday gifts. There’s also a Kindle edition of both Making It and
The Urban Homestead if you’re e-inclined.

Even if you just click through our Amazon bookstore (on the right column) and don’t buy any of our books, we get a cut of any subsequent Amazon purchases you do make. Really! Strange but true. All proceeds go towards kibble and cat litter.

Deadly Nightshade vs. Black Nightshade

I spotted the sign above at the Heirloom Festival in Sonoma. The sign made the claim that “deadly nightshade” is actually a choice edible. Unfortunately, there’s considerable confusion over the popular name “deadly nightshade.”  The plant most commonly referred to as “deadly nightshade,” is Atropa belladonna, which is a highly unpleasant and toxic hallucinogen. “Black nightshade,” Solanum nigrum, on the other hand, is edible. The potted plant below the sign was Solanum nigrum not Atropa belladonna. One must be careful when using the popular names for plants!

Solanum nigrum

To add to the confusion, Solanum nigrum is eaten and used as animal fodder all over the world, though many sources continue to describe it as toxic. As with all members of the Solanum family there’s still a great deal of superstition when it comes to toxicity. Remember that many Europeans considered tomatoes to be poisonous well into the 18th century. Even today tomato leaves, used by my Filipino neighbors as a seasoning, are still labeled by many as poisonous. An interesting article in the New York Times “Accused, Yes, but Probably Not a Killer” busts the tomato leaf toxicity myth.

Atropa belladonna – don’t munch on this one!

The confusion over the case of the alleged toxicity of Solanum nigrum may stem from our lack of  intimacy with plants in the West. The use of Solanum nigrum by indigenous peoples is actually a bit complicated. Different soil conditions can, it turns out, produce some toxic alkaloids in Solanum nigrum. Cooking eliminates the alkaloids.  Jennifer M. Edmonds and  James A. Chweya, writing for the International Plant Genetic Resources Institute, describe the uses of Solanum nigrum and end up advocating for its widespread use as a cultivated food source. Here’s what they say about it’s toxicity in their book, Black nightshades, Solanum nigrum L. and related species, which you can read in Google Books,

. . . the comparable number of accounts reporting that these species [Solanum nigrum] are harmless as food and fodder sources suggest that this toxicity is variable. Indeed a chemical suvey of various members of the section Solanum reported the presence of potentially toxic alkaloids only in unripe fruits, with ripe berries and vegetative parts tacking these compounds. Shilling et al. (1992) therefore concluded that the plants are probably only poisonous to indiscriminate feeders such as livestock who might consume the whole plant. However, these plants are browsed and used as fodder for animals without any detrimental effect in some areas, and Rogers and Ogg (1981) suggested that the development of toxic levels of these alkaloids is dependent on their growth under certain conditions or in certain localities, and even on the age of the plants concerned. Other reports suggest that the amounts of poisonous ‘princinples’ vary greatly with climate, season and soil type (Cooper and Johnson 1984). It is highly probable that boiling destroys any toxicity inherent in these species; most ethonobotanical reports of their use as vegetables refer to cooking, boiling and even repeated boiling with the liquid being discarded; similar reports of the use of berries also refer to their being poisonous when uncooked or unripe. Drying, however, does not destroy the toxicity of the solamine-type alkaloids (Everist 1974). It is these glycosidal alkaloids which are responsible for the bitter taste often associated with the Solanums. 

The Solanum nigrum growing in our backyard.

A few Solanum nigrum plants popped up in the yard last month and I’ve let them grow. While I can’t say that I’m a big fan of the berries, I’ve tasted them raw and lived to tell the tale.

The Secret to Barefoot Running

Born to Run author Christopher McDougall had a provocative piece in yesterday’s New York Times, “The Once and Future Way to Run” about a simple 19th century technique for teaching good running form. The “100-up” drill McDougall describes forces a runner to land on the ball of the foot rather than the heel. Even though I’ve switched to barefoot running I still heel strike occasionally, a habit caused by a lifetime of wearing cushy shoes. I’m gong to make this drill a regular part of my fitness program. 

The article also takes a jab at Rodale’s Runner’s World magazine which, apparently, hasn’t ever seen a shoe it didn’t like. Multi-million dollar advertising contracts with shoe companies just might be the reason why. This is a common ethical lapse in fitness journalism. A local free running rag I picked up had a cover story on barefoot running which was all about . . . minimalist shoes! In two years of running with no shoes at all (i.e. barefoot) I have yet to get even a scratch.

Click on the article link above to see a helpful video showing the 100-up drill.

Too Much Phosphate

Symptoms of chlorosis. Image from the Washington State University

Our possible backyard lead situation is a good reason to get a soil test, but if that didn’t convince you the Garden Professors at Washington State University just blogged about another important motivation: the bad effects of too much phosphate.

An overabundance of phosphate can interfere with a plant’s ability to uptake iron resulting in interveinal chlorosis, a yellowing of the leaves between the veins. So adding fertilizer that contains phosphate to soil that doesn’t need it is a waste of money, damages the environment and can kill your plants. Of all the soils I’ve tested in Los Angeles, all are already high in phosphate, meaning that most fertilizers, both organic and chemical are both unnecessary and potentially toxic to plants.

As the Garden Professors also note in another post, it can be very difficult to diagnose problems just with visual cues. Chlorosis, for instance, can also be caused by other factors.  As Garden Professor Linda Chalker-Scott puts it, “You can’t fly by the seat of your pants on this one, folks.” While I’m probably a bigger proponent of intuition and “woo-woo” than Chalker-Scott, I think it’s a good idea to balance our left and right brains. No reason you can’t get a soil test and talk to those plant Devas.