Saturday, October 17, 2009


The finishing touches on the cob cottage have been pushed to the back burner over the past week, replaced by a quick and dirty backyard makeover project. My family down here (Elaine, Doug, and Ian) just recently moved out of their small loft apartment and across town into an even smaller Craftsman bungalow.

The house was vacant for a good while (the exact time frame is still unknown - my guess is 22 years) and subsequently was in need of repair. The house looks great after a summer of renovation, but the backyard, as of a week ago, had a much darker story to tell. Doug and Elaine hired me and my cob colleague, Danielle, to do some transformational design/build work.

Here's what we started with:

(above) looking back from the gravel driveway
(below) view from the back of the yard

The first step was to clear out anything green that wasn't a big tree - to give a sense of what we were working with in terms of terrain, soil quality, and shapes of spaces.

Notice Danielle's sinewy neck.

You can see in the photo above that our clearing work led to the discovery of some trash. Unfortunately, the photo does not at all convey an idea of how much trash we found. At least 22 years worth of it.

Here is the front panel of a car (that was completely below ground level):

And here is a truck bed full of the other scrap metal that came out with it:

We took this metal to a recycling company and (ecstatically) received $30 for it.
If you've ever gotten rid of a dishwasher, car, or steel rod, this is where it is:

We also took two heaping truck loads of yard waste to Durham's disposal center, and a load of trash. The vast majority of the trash was not sitting on top of the soil, waiting to be picked up - it had to be unearthed and then removed by axe, mattock, pick, sledge, or raw human grit strength.

The main idea of the whole yard is to create a space for the dogs to run around in, and a play space for Ian (and other humans). To accomplish this, we decided to break up the rectangle of a yard with a voluptous cob garden wall.

First, we laid out the shape of the wall with bricks. This allowed us to run up onto the deck (where the photo is being taken from), get a view, and then go back down and readjust them. Eventually, we realized our curves. The wheelbarrow and I are in Ian's space, and the dogs will have the yard surrounding Ian.

Last Sunday was trench day. Doug, Danielle and I dug a trench following our line of bricks.

The trench was then filled with gravel and 4" perforated drainage pipe (just like the trench underneath the walls of the cob cottage, except much smaller). It will perform the dual function of providing the wall with a solid footing below frost line, and acting as a drainage system to expediently move any water away from the wall.

Once the trench was filled, it was time to lay a foundation for the wall. Because of time pressure (I am leaving North Carolina in 5 days), we decided to use concrete block. The intention is to have a wall that is half block, and half cob. The block will be stuccoed, and the cob will receive an earthen plaster, giving the wall a two-tone look.

Laying block:

Although using concrete is the ultimate sin in the eyes of many natural builders (including myself), Danielle and I had fun with it. Neither of us had any experience laying block before that morning, and we ended up with a satisfyingly gorgeous and solid wall.

Next came cob. We had been intending to use a mortar mixer to mix the cob (another, lesser natural building sin), but found that the mixer we had wasn't quite right for it. We would have had to mix really wet batches, and wouldn't have been able to get much height on the wall each day (a wall of wet cob will slump and squish under too much of its own weight). So in the face of 49-degree days, we took off our shoes and began the dance:

Because the soil from the backyard was full of glass, metal, and other assorted foot dangers, we had to source soil elsewhere. So it is with urban cob. We found a very local Craigslist advertisement for "free fill dirt," and have been taking loads of it. I am quite pleased with the quality of our cob. Its gray color looks totally different from the bright red/orange cob we made for the cottage, but it's just as strong (and beautiful! the clay in the soil ranges from gray, to purple, to deep red-brown).

Speed cob. As the cobber, I keep my head up and cob with fury. As the thrower, Danielle balls up the cob as quick as she can and whips it to my open palm.

Above is a deadman in the wall - a gnarly chunk of roundwood that we buried in the cob. This will allow us to attach a wooden frame for a gate later on.

We cobbed bottles into the wall (we excavated dozens and dozens of bottles in our initial clearing of the yard - one of the nearby houses used to be a pub). Sometimes people cob in bottles with the intention of letting light through, but we were just using them as filler - to get a higher wall, with less cob.

This will be the entrance into Ian's space. We will make it grand.

More photos soon.

Wednesday, October 7, 2009



So far, the biggest hurdle in the finishing process has been the earthen floor. To make a long story short: we poured a shiny, smooth, level, gorgeous floor 3 weeks ago. The following morning, it was depressingly full of cracks. Various efforts have been taken since then to return the floor to its original glory, but the cracks kept coming back.

We fixed the floor on at least three different occasions, and it wasn't an easy process. A floor-fixer must "float" himself out across the floor on a pathway of boards and insulation foam - this is to spread out his weight so that he doesn't leave deep impressions in the new and malleable earth. He must start at the side of the room opposite the door, and then work his way back, digging out, filling, and troweling cracks as he goes. Most of the work is done in a squatting position. He travels with a bucket of floor mix, a bucket of water, a trowel, his patience, and deep chest strength ("core" strength, if you will). Despite his best attempts at spreading his weight, it's near to impossible not to leave impressions from the boards he is standing on - so in addition to cracks that he's fixing, he must trowel over all of the board marks he leaves.

Mike claimed to like the process, but he is into yoga. I found it tedious and awkward.

Below are the infamous cracks. It is interesting to note that the floor was consistent in its cracking. It was always the same pattern, never any cracks in new locations.

I started thinking that maybe the problem was that our repair process was just covering cracks that still existed beneath the surface. In theory, as the floor continued to dry (and the clay to shrink) the buried cracks would continue to widen, pulling apart the material directly above them and causing new visible cracks in the same spot.

We finally decided to just add an entire new layer of floor. A very thin layer, about 1/4" thick. Again, it came out looking spectacular. A day after this, Mike left for New York and I left for a week to visit my family in Durham. Upon my return to the cottage, I was confronted with the same cracks in the new layer.

I decide that maybe downward force was the best solution, because it would potentially compress material into filling each entire crack while simultaneously allowing me to release my aggression upon this unruly beast of a problem. I took the hammer to a crack, troweling over the hammer marks to smooth it back out. This ended up working surpisingly poorly, as the crack came back within half a day.

This past monday, I decided that I needed some sort of blank slate for this floor process, and so I ripped up entirely the newest 1/4" layer. My intention was to get down to the first layer, fill whatever cracks were there with sand (because by this point the original layer was dry, and so the cracks were done expanding), and reconsitute and re-install the top 1/4" layer.

I dug it down to this:

And I liked the look so much - mottled and rough (and relatively crack-free) - that I decided that it should be celebrated as the final floor! The appearance was refined a bit with a session of hard-troweling:
The hard troweling is just what it sounds like. Taking a trowel (and in this case a little bit of water, because the floor was so dry by this point) and giving the floor all hell. It really helps to use two hands, and allow your body to fall into the sweeping motions, aggressively putting all of your weight behind it. What happens is that material is being moved, and molecules aligned, resulting in a surface quality that is smoother and sealed.


After:In the second photo, you can see that the general surface is smoother. Some sand and fiber particles have been pushed out, and are now laying on top - this is fine, because they will just be swept away before the floor is finished and sealed with a treatment of linseed oil and beeswax.

What a relief to have a beautiful, dry floor.

Sunday, October 4, 2009


We still don't have a name for the cottage, but I thought it might be nice to put a symbol of some sort above the door. Because Margaret planted two fig trees out front as part of the passive solar design, I went with a fig leaf (although most people see it as other things, like "a baby," or "a nature shape.")

Often in strawbale homes, a builder will pick a place to put a "truth window," a piece of glass right up against the strawbale wall. This allows the homeowner to prove that their house is built out of straw, in the case of disbelievers. The fig leaf acts as a cob truth window (sans glass), the only place on the entire cottage where the original cob is showing through.

With the door, which will be painted (Margaret's vote is deep blue):

I decided to do a bit more lime, for an especially grand entrance, like walking into a flower. This is right after I scratched and hydrated the areas to be plastered, to provide a good surface for adhesion:

You can see how the scratch marks will give the lime plaster some "tooth" to grab onto:

Sunset is when the clay really gets to show off its color:


Because the earthen floor has been layed and is now drying (and can't be walked on), it is tough to get photos of the interior. Luckily, Mike and I decided to incorporate a brick floor extending from the entrance to the woodstove hearth. This has provided a countless number of benefits:

1. One can still step inside while the floor is drying - I can take photos, visitors can take a peek, we can store tools safely inside at night, and I can sleep warmly on the brick on the cool nights that are becoming more and more common as we move into October.

2. With brick taking up 1/4 of the entire floor, we were left with less earthen floor to do: fewer materials to haul, mix, and pour.

3. We had to custom cut all of the bricks that run along the wall - we also decided to make the transition between the bricks and the earth a really voluptuous "s" shape, so we had to cut those too, which provided us with our first opportunity to get some beers and work late into the night with some extension cords from the solar panel and a light. It was great to see the cottage lit up at night.

4. As a personal benefit, I really enjoyed using the brick, and love the look. It went straight to the top of things I want to use on my next project.

I'll get a better photo of the brick once I can walk across the floor, but here's the best peep:

The Northwest corner:

The Southwest corner. I love the orange light on that window reveal at dusk.

The Evil Chicken and his friend, the Footed Toothfish

It's been quite a while since I've had an operable camera on the cottage site, but those days are over(!). The building has gone through a number of visual changes in the past couple of weeks. My latest undertaking was purely for aesthetic value - both to cover up cracks in the red earthen plaster, and to add general character to the otherwise plain north and west walls.



You may be thinking: "but, but, but it looked pure, and simple, and beautiful before the mural. Now it's a bit too much; visually overwhelming, even. It takes attention away from the gorgeous foundation stones, and adulterates the curve of the roof."

I've thought the same things. However, it was an experiment, and a fun one at that. I don't think I'd ever do it on my own house.

But as far as positives go: it makes the house very unique - I specifically avoided certain subjects in my mural that I find corny and overused: hands, the sun, moon, stars, happy faces, flowers. It looks especially good from far away, like in the garden, which is where most people first see the cottage. I hope that it draws crowds down through the garden fence to get a closer look. Most importantly, the lime plaster covers up all the unsightly cracks that opened up in the earthen plaster beneath it. In fact, the shapes in the mural (including the Footed Toothfish and Evil Chicken) are based on where the biggest cracks were that I wanted to hide. The art created itself as I went along.

The earthen plaster had to be scratched and partially saturated with water to provide a good bonding surface for the lime plaster.

Here is the gardener's view (the origin of the mural is where the stove pipe exits through the wall - it's supposed to be like flames and monsters are shooting out from the pipe and around the wall, kind of) :

The drying process for the lime plaster was really neat. The plaster is actually mostly sand (1 part lime putty, 3 parts sand, 1/2 part horse manure). As you can see below, the freshly applied plaster is more the color of the sand, but the white lime completely takes over the color as it dries.

I don't know much in detail about the process that lime goes to - Mike is always able to explain it more fully (he was a chemistry major). Basically, limestone is mined, crushed up, and then heated in an extremely hot kiln. During this heating process, CO2 is released. (Then a lot more happens....) When you buy lime in the United States, it is sold in dry, powder form. The powdered lime is "slaked," which means that it is mixed with water to form a putty. The putty is stored under a layer of water to prevent it from being exposed to air (which will cause it to harden). The longer the putty is stored, the better it gets (can't remember why) - the putty I used has been sitting in a 55-gallon drum for 4 years! The putty is mixed with sand to make a plaster. When the plaster is applied, the lime pulls CO2 back out of the air, and goes through a chemical change, turning it back into "stone." So a coat of lime plaster on a wall is essentially a coat of really thin (and breathable) stone. It is more durable than an earthen plaster, which is why we used it on the exterior window sills (no photos, sorry) where rain water might sit for longer than on a vertical wall.

Up close, the lime and earthen plaster look very similar in terms of texture. This is because they are both mostly sand. One has clay, one has lime. Both have a little bit of horse poop, which provides tensile strength (if you ever pulled apart horse manure, note how it's mostly all grass, broken down into short bits). When I first started to touch and break up horse poo, I was a bit disgusted. Once I started thinking of it more as "grass that has been processed through a most beautiful machine using natural enzymes," it wasn't bad at all. In a plaster, the grass acts to hold things together and prevent cracking once the clay starts to shrink. It's like the rebar in concrete, but on a tinier scale.