Living earthberm ramp to living roof

Side view with tire retaining wall
Side view with tire retaining wall

After drawing the earthberm ramp to the living roof with tires of rammed earth, I saw that it would take about 150 pounded tires to create a retaining wall for the earthberm ramp. Recalling the May 2011 strawbale build for the llama shed, it took us a day and a half with 11 people to pound the 47 tires in the foundation. At that rate, it would take us at least 4 or 5 days just to build the retaining wall! That’s a lot of tire pounding for such a small structure.

In an effort to solve the issue of “how do we avoid pounding tires for 5 days”, I searched the internet for other ideas. I found out that someone has built a retaining wall by stacking unopened cement bags in a running bond. When it rained, the moisture was sucked in through the paper bag and voila, a cement brick wall was formed! It’s a great idea, but at $5 per bag and with at least 200 bags necessary for the wall, it’s well out of budget for this project.

The next “easy way out” idea I had was to just set strawbales in place for the retaining wall, cinch them together, use the usual mud mixtures on them and fill in the ramp. I knew this idea sounded far-fetched because I suspected the outward pressure of the soil against the wall would be too great for the weight of a strawbale wall. I searched Andrew Morrison’s to see if others had ever tried an earthberm strawbale wall, and Andrew suggests that any buried wall be made of concrete block or something similar that then transitions to unburied strawbale walls. Concrete blocks are also out of budget for this project, at $3 per block and about 125 blocks, we’d be at $375 just for the retaining wall.

And, of course, there is the classic milled stone retaining wall. If we can’t afford bags of concrete or concrete blocks, I know milled stone is out of the budget.

Then, the idea of earthbags entered my mind. My neighbor has been toying with the idea of earthbag construction for a while and has a book that he’s let me look through. Filling bags with earth seems like an easier process than pounding tires, and I have access to free burlap sacks from a local coffee roasting company. Perhaps the smell of coffee will stimulate the crew to fill them faster! The website indicates that burlap bags will rot with moisture, but I think that since most of the earth material at Blue Rock Station is clay, it will form bricks that stay in place and rotting burlap should not affect the integrity of the structure. The sacks would then be covered with the traditional mud mixtures and the interior face of the retaining wall will have a vapor barrier of 6 mil plastic similar to the one used in the foundation of the building. If the deterioration of the sacks are a concern for Annie & Jay, we can use woven polypropylene feed sacks available from any large scale agricultural operation. I’ve located a few examples on Craigslist for about $0.19 a piece.

My model indicates that it would take about 225 earthbags to build the retaining wall. I haven’t timed how long it would take to fill an earthbag, but my guess is that it would take less time to fill 225 earthbags than to pound 150 tires.

Another addition to this rendition of the model is the tin roof from with rainwater is diverted to a rainbarrel within the bottle-wall cone. A drainage system for this handwashing station is yet to be devised, but I envision a sink built into the wall with PVC piping draining away from the building to a French drain.

Below are the latest images from the model, and as always, make sure to check my website at for further updates and model images.

Front Right View with earthbag retaining wall
Front Right View with earthbag retaining wall
Front side view with earthbag retaining wall
Front side view with earthbag retaining wall
Rear Left View with earthbag retaining wall
Rear Left View with earthbag retaining wall
Rear side view with earthbag retaining wall
Rear side view with earthbag retaining wall

Progress on the roofing systems

I’ve made a bit of progress on the roofing systems of my Glorified Privy building. I says “systems” because there are two roofs on this building – a living roof and a metal roof from which to collect rainwater. I’ve learned a lot about living roofs in this past week, studying cases online and in books. I figured out what sort of plants do well in 4″ of soil in our climate that also self-seed. I’ve also spoken with the family civil engineer and figured out my dead and live loads for the living roof, which gave me a good idea on the type of lumber I need to use, and how far apart the rafters need to be to support the loads.

There were a few areas where I differed from the usual living roof construction methods. Annie had suggested bitumen as our waterproofing membrane, but further research into the subject has led me to not choose this material. Since “asphaltic bitumen is an organic material, roots can naturally attempt to penetrate the surface while seeking nutrients” ( A common practice in the industry is to pour a concrete slab over the asphaltic birumen to prevent this from happening. Since our budget cannot support the purchase of I-beams to support the weight of a concrete slab, this building will use a double layer of 6-mil plastic as the waterproofing membrane for the living roof. The 6-mil plastic is the same material we use for the vapor barrier between the tire foundation and the strawbales, so we will already have this material on hand.

Another area where this design will differ from conventional living roofs is the drainage layer. Most living roofs use gravel or lava rock as the drainage layer. Others use pre-fabricated plastic drainage layers. We’ll be using a low-tech option – biscuits of straw. They are lightweight, allow water to drain, easy to install, and readily available during our build. One disadvantage of this method is that the straw will decompose and will need to be replaced every few years, so the entire roof will need to be shoveled out and re-planted.

I still haven’t modeled my living earthberm ramp to the living roof, but that will come next in the design. For now, here are a few views of my model to satiate your curiosity. And as always, check my website at for more updates

Back of Building View
Living Roof & Entry view
Front Entry View

Designing a building isn’t easy!

As a brief interlude to Annie & Jay’s Thanks for Nothing Month posts, I wanted to share some of the progress I’ve made on the strawbale design we’ll be building in May.

Here’s a sneak peak at how things are coming along:

Glorified Privy in 3D, roofless
Glorified Privy in 3D, roofless

I’m two revisions into my design for the strawbale composting toilet building and I’ve discovered a few things:

  1. I don’t know enough about living roofs
  2. It takes a long time to design a building

For point number one, I’m struggling with my roofing system because this roof is not only supposed to support the weight of a fully saturated living roof with plants, but also the weight of two or three people and perhaps some lounge furniture and some safety railing to serve as a scenic overlook.

For point number two, I’m over twenty hours into the actual design process and I haven’t even gotten to hashing out the particulars of the pathway that spirals around the building to the top of the overlook! However, some of this time is due to my unfamiliarity with Google SketchUp, the 3D software I’m using to design my models.

At this point in my design process, I’ve got a few things figured out. I know for sure that to accommodate the size of the toilet and to still follow the ADA requirements for an accessible stall, my building will have an interior footprint of 115″ x 61″. I’ve also reconsidered the rounded east walls due to complexities in the design process (and personally thinking it’d be too hard to accomplish in such a quick workshop).

Hopefully a few phone calls with the family civil engineer will help me determine the correct support structure for the living roof, and progress on the design can continue.

As always, you can follow more of my progress and further notes on