Urban forest cob experiment part IV: drainage & foundation

I realize that in many ways posting photos at this stage of my “cob house” development is much like sharing ultrasounds to announce an impending child. At a hint of future potential, people kindly shower enthusiasm and encouraging words.

Certainly, Cobina is just a shell of her future potential at the moment, with no cob in sight to coddle (cob coddling: it’s a real thing) – yet, somehow, it was still exciting to make our first two gravel runs this week, thanks to neighbors Harris and Natalie’s truck.

Gravel run
Fully loaded with gravel at the Rock Shop

We were not able to buy the round drainage rock recommended in the book,  nor were we about to raid the Eno River, so instead opted for the common (57?) drainage rock recommended by the Rock Shop on Hillsborough Road.

We bought 1/2 cubic yard, then returned for 1/4 cubic yard, and it was just enough for our 12’x12′ circle and runoff.  I loaded up about 100 wheel barrows from the truck to the site, up the non-ramped stairs and through my obstacle-coursed yard.

I recommended wearing sunglasses when shoveling up gravel as a piece flew in my eye mid-shoveling; I quickly added these and didn’t have any more problems. I did feel pretty strong after a few days of heavy labor, until I counter-acted calorie loss through late-week cupcakes via Rob.


Before and after the first layer of rock, I needed to tamp the ground/gravel. Rob made a handy tamper with a broom stick and short board.

Tamper man
Tamper man
Pre-gravel tamping


After the tamping, it was time to lay the pipe (some of which was kindly donated by Matt & Bonnie – thank you!), make sure it is sloping down toward the lowest point and outlet, then cover it with an inch or two of drainage gravel.  In some spots, the pipe was quite near the ground, but I think we’ll be OK.*


*this is based on uninformed optimism.



And with this I present to you, still no cob, but a glimpse into Cobina’s arrival with the laying of “shoes” or the beginnings of her foundation. I was going to use our neatly stacked brick there in the background, but Rob suggested I use up our heavy chunks of brick wall first since they would not be showing as much.


I had to measure as I went along to make sure I was still laying the foundation within the 12′ x 12′ allowance.  I found that the building was a bit too long East to West, so part of the drainage on the West side will now be a “curtain” style drain — which is fine as it is also the entrance.

Entryway to future cob home.  Just ring the doorbell.


I also outlined the required thickness of the foundation (15-16″ at the base, tapering off thinner as I build height) as well as the future “foundation” of the cob couch with scraps of brick, clay pipe, and gutter.


Had a little less time to work on Cobina this week as I spent most of Friday preparing our (treacherous) back yard for about 40 people attending our first neighborhood-meeting-in-the-back-yard event.

It was awesome! Cob building site (blocked off) to the left, out of photo …
Rob BBQ’d 40 Delight Soy Chicken patties. Delicious!

This weekend, and in preparation for new tenants moving into the front of our house, we moved some of our old furniture to our pallet deck and enjoyed some time outside. Still need to paint/finish the deck and pallet furniture.


Next week, I’ll be rounding out the foundation, puzzling in and test-walking on the brick to ensure it’s stable and 15-16″ thick.  Usually people use stone or urbanite for cob foundations, but since we have so much left over brick from our old walls, I decided this was the way to go (and brick is an acceptable material to build a foundation based on my research).

I also decided to use some mortar for the bricks, so Rob picked up two bags of Portland Cement and 4-5 bags of sand which I’ll be using next week at a 1:3 or 1:4  (Cement: Sand) ratio.  Some people also use cob cement or “soil cement” but since I’m fairly new at this I’d like it to stick and keep some of the critters at bay.


Costs this week:

  • Gravel: $55
  • Portland Cement: $16
  • Sand: $15


Total cost to date: