Urban forest cob experiment part III: trenching, leveling, sloping

(Better) trenching

I didn’t realize how lame my trench was until I dug a better one.  I tend toward “that’s good enough” so try to purposely focus on what I’ve read/researched and match that with my work to ensure I’m on track (or being lazy).

A level floor. A better trench.

A (more) level floor. A better trench. Some gloves.

This week began with tearing out vines then hauling wheelbarrows of bricks (see pile in photo above) from the old wall in our front yard that fell when our tree trunk was removed a month ago.  I plan to re-purpose the bricks for my foundation wall.

I didn’t plan on getting poison ivy, but that happened too.

Ouch. Itch. Ouch.

Ouch. Itch. Ouch.


Leveling the site

I also realized/read that I need a level site (doh!) so spent quite a bit of time with my digging shovels (squared and pointed) and mattock leveling out and scooping up the land on my future floor, removing the grass and roots.

I’ve used the mattock with my non-dominant (left) arm/side as well to both build up my strength and avoid getting an injury from overuse.

Sloping the trench and testing the slope

I attempted to perfect the slope in my drainage trench, making sure the water will flow down and out. The rule of thumb is 1/4″ drop for every 10′ of length – which will also be something I refine when I get the drainage rock next week.

Sort of sloping the right way, level says

Sort of sloping the right way, level says


To test the slope, I used water from our A/C unit condensate drain line (that pipe that sticks out of your house and drips water) by placing a bucket there earlier (which we usually use to water plants) and then pouring into the dug trench.


Water, waiting


Oops, missed a little bit.  But it did flow down to the right.

Poured water

Poured water


Resulting site by Friday

Here is the happy site by week’s end.  Leveled and trenched. Noticeably crooked due to camera angle. Note the outgoing trench top right (I’m thinking of making a small pool/pond for the water runoff.)


Drainage almost ready


In between the outside work, I’m reading the two aforementioned books on cobbing as well as checking online blogs for more information. I was hopeful when I read the authors of The Hand-Sculpted House report that not only did they start their first cob house late in the season (September) but they finished it by mid-November, and this is in Oregon where it’s damper and presumably takes longer to dry.

I also was encouraged by reading a rough estimate of how long it takes to actually build with cob.  Someone new and inexperienced (insert selfie here) can probably build a few feet per week!  So with this new knowledge I created a timeline.

My timeline

The following is very rough based on my limited (but growing) understanding of the process.

Item / End date

  • Drainage: Aug 20
  • Foundation: Sept 1
  • Cob, 2 feet/week: Sept 7 – Oct 7
  • Roof: Oct 15 (some people erect this now to protect the cob, but I’ll be using tarps)
  • Sculpt: Oct 15 (and throughout)
  • Floor: Nov 1
  • Finished: mid-November

So there it is, all out there bold, claimy, and confident.  Will I finish by mid-November?  Absolutely no idea.  But I’m going to try my best. These weekly updates help keep me to task.



I also sketched out an updated version of the layout, with life-size adults (Rob and I?) within the 12′ x 12′ walls.  As you can see, I was an English major.


I’m not sure who the other two folks are


Other benefits of (preparing for) cobbing

Working in our yard I notice more than I would just passing through as I have in the past.  The little butterflies, small brilliant blue worm snakes, the bird call and responses, the dog poop I failed to pick up, and our little shiitake log still producing shiitakes even after a couple of years.

Oh sweet log.

Oh sweet log.

At a rate of about 2-3 mushrooms per season, the log is not really a sub for buying them at the store.  But they were beauts.



Costs this week:

Extra 4″ drainage pipe: $6

Total cost to date:


Next week, I’ll be hauling drainage rock courtesy of a kind neighbor’s truck, and getting started on laying the drainage and then foundation.  I’m super excited about this project and also look forward to enjoying the company of a friend who offered to join me on Fridays once the cob gets started.

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