On July 11, 2009, I moved into my newly completed cob house. It’s now been over a year since the move-in, and there have been many learning lessons along the way. I’d like to present a number of those lessons here in my one year report of living in a cob house.
Here we go…
Here it is…. the first food from the sod roof of my cob house. Mm mm.
At long last, I have a living roof! I’ve been anticipating this day for over a year now and it’s finally done. On Monday, a group of about twelve folks assembled to help me lift sod onto the top of my roof, and in two and a half hours, it was effectively covered.
Lately I have been focusing a lot of my attention on building the living roof (a.k.a. green roof, sod roof, or turf roof). Last week, I finished building an edge board – a sort of retaining wall around the perimeter of the roof to help hold the soil from sliding off the roof. I debated quite a bit about how to construct the edge board, and eventually I decided that I would use round black locust logs spiked into the rafter ends with giant 8″ nails. Unfortunately, the logs only extend a couple of inches above the height of the roof, so it’s less of a retaining “wall” and more of a little edge “bump.” (See above photo for a better idea.) I’m not too afraid of soil sliding off the roof, so I’m not that worried.
It feels like building season is almost upon us. There’s a hint of spring warmth in the air, and I get antsier with each passing day as I think about the prospect of finishing my humble abode. I have a building sequence of events that I’ve been thinking about today.
Other than finishing the living roof (I won’t load the topsoil until the spring rains have largely passed, so I’m not in an immediate rush to finish the other roof work that remains), there is a fair bit of interior work to be done.
I will be headed out of Dancing Rabbit in three short weeks to go back to New Jersey for the holidays. Within the past couple of weeks, I have accepted the fact that I will not absolutely “finish” the house before that time. By “finish”, I mean complete the roof, finish the floor, make my rocket stove and cob bed and bench, and plaster the interior.
So. I’ve done some prioritizing. Now that the cob walls are complete, and the windows and door are in, the house is sealed. My biggest remaining priority is the roof – I need to construct an edge board around the roof, create a soil-retaining system, and have soil moved to my site and load it onto the roof. Oh, and seed the soil, too. That’s not a small load of work by any means!
Before the EPDM went on the roof, I wanted to add a cushion of cardboard on top of the rafters and decking to protect the membrane. And before the cardboard went on, I wanted to add some kind of fabric so that the cardboard would not be visible from inside of the space. I bought a 50 yard bolt of muslin for $50 at Zimmerman’s, and Karen (my current work exchanger) and I draped the fabric and stapled it to the decking.
Last week, I ordered the most expensive material for my entire cob house: the EPDM pond liner for my (soon-coming) living roof. EPDM is a synthetic, petroleum-based rubber product commonly used for living roofs, due to its strength and durability. Apparently, it can last 50 years exposed to the sun, and presumably longer buried under dirt.
I have not been thrilled by the prospect of purchasing this petro product for my house (it’s one of the few new, synthetic materials in the whole building); however, it has been challenging to find information on building a living roof using natural materials. Apparently, Norwegians have historically used birch bark as their impermeable membrane. Getting more information than just that has proved difficult, and still, I probably wouldn’t have been willing to experiment with my first house, considering just how important a good roof is. I want to do this right. Perhaps I’ll experiment with an all-natural living roof on a different building in the future. (If anyone out there has details on any books, etc. with information on traditional living roofs, let me know!)
Anyway, the 35’x35′ sheet of EPDM cost a whopping $622, at least $100 of which was the shipping cost. The thing weighs 380 pounds. I’m pretty daunted by the idea of somehow getting this whole thing unrolled over the roof… but I’m sure with enough hands, it won’t be so bad!
The past few days, I have been dwelling quite heavily on the roof design for my cob house. I will be constructing what is called a reciprocal roof, a self-supporting structure composed of pin oak and black locust poles. Reciprocal roofs are round and spiral-y, perfect for round structures. They require no center post and are apparently “simple” to construct, requiring no experience. Plus, they look great, too.
The only downside to building a reciprocal roof is the apparent lack of really comprehensive information out there on how to actually do it. Running a Google search for reciprocal roofs results in a few decent hits, but still, there seems to be a dearth of hard information on how to go about making a reciprocal roof from start to finish.
The best resource I have found thus far is Tony Wrench’s book, How To Build a Low-Impact Roundhouse. You can see some photos of his design here. Wrench has some good sketches and a decent amount of how-to information in his book (which, by the way, is pretty hard to find), but I’m still craving more. Perhaps because my case is pretty different from his and I want to be reassured that this thing is going to work.
The main difference being that my walls are load-bearing, with the reciprocal roof rafters resting directly on the cob walls. Oh, and my house is also not totally circular… That makes a big difference, too.
But anyway, here are a few other sources of images and information for the prospective reciprocal roofer:
This is mostly what I have been reading and looking at for inspiration. I guess the only way to determine if my own reciprocal roof design works is actually making this thing. Soon enough, I will know!
(Image from Zone5.org)
Hi there, I’m Ziggy. In 2008, I launched The Year of Mud while building my first natural home. This website is a collection of personal stories and experiences building with clay, straw, and wood over the past 15+ years. A few of the things that get me fired up are natural plasters, timber framing, & Japanese architecture. In 2012, we started offering Natural Building Workshops, so you can learn essential hands-on skills to build your own natural home.