Film on Cob Building

A link to this film on cob building was posted over on the Coblist mailing list. First Earth is a very worthwhile film to watch. While I don't buy all the "Peak Oil" language, the film makes some great points about sustainable building. Enjoy.

Wow, isn't this inspiring!

Work and family obligations have pre-empted my former lofty plans to build my own cob home, but this sure is inspiring. Likelier than not, I won't start my own project in earnest for another 5 or 6 years, but I continue to dream. Check out my current inspiration.

Beginnings of My Solar PV System

Contrary to my earlier plans, I went ahead and bought a couple of solar photovoltaic panel "kits" and an AC inverter at Harbor Freight Tools this weekend. Each kit contains 3 15 watt amorphous solar panels, a DC Controller, and a couple of 12v Compact Flourescent lights. These kits were on sale for $179 each. The panels, at roughly $4 per watt, are are a cost effective alternative to silicon solar panels, which are usually 6-7 dollars per watt.



Amorphous solar panels, from what I've read, work better than silicon solar panels when partially shaded - as my cob house will be in partial shade in early morning hours. These panels are also reputed to be more resistant to damage from hail or even bullet holes (I don't plan to be shooting any bullets at them though ;-) ). The downside to this type of panels is that they are a little larger than equivalent wattage silicon panels.

Next, I will be looking to purchase a Morningstar SunSaver Solar PV Charge Controller and a battery bank, and I'll have a minimally complete starter solar PV system.

At 90w total output, this array won't be enough for my eventual needs, but it will do for starters, and I might double the number of panels at some point.

I intend to install these panels on the roof of the current "stick-built" cabin so I can run a couple of small appliances, fans, and lights at nighttime. I probably won't visit my property again until September when it starts to cool off a bit, so I've got a little time to shop for the batteries I'll need.

Rainwater Catchment & Filtering Systems

Ran across an interesting news story on imported German rainwater filtering/treatment systems. These systems use UV treatment to kill bacteria, so require electricity to operate. Not a problem once a PV electric system is installed, but I'm not sure I'll get to that in phase one.

I guess I'll file this in the "more research needed" folder.

Building in Phases

This week I recorded an episode of the Discovery Channel show "Dirty Jobs", and got my wife to watch it with me. The episode was titled "Brown Before Green", and one of the segments featured the host building a cob house.

Now this was my wife's first exposure to cob building (although she's listened to me talk about it till she's sick of hearing about it), so maybe I picked a poor introduction for her. After all, the host of this show is obviously focusing on the nastier aspects of work, in this case working with mud. But I wanted her to see the process of building cob at it's worst and see how she reacted.

To my pleaseure, my wife wasn't really put off by the dirty nature of the job. But it really struck her just how labor intensive cob building would be. She commented that I'd only be able to work for six months of the year (too hot during the summer, too wet during much of the rest of the year). Since I'll only get a couple of weekends per month to work on it, at best, given the distance from home, that comes out to about 12 weekends per year that I'll be able to put in, and that is probably overly optomistic.

"It will take you two or three years to complete a cob house at that rate" my wife predicted.

I think she's right.

So I had an epiphany - I'll build in phases. I've long had a rough sketch formed in my mind, but haven't been able to translate it into a drawing I was happy with. Building in two phases will force a solution to a couple of design issues I've struggled with, and helps me solidify my plans. And, more importantly, it will enable me to structure the work in manageable chunks.

I want a large ground floor and a moderately sized sleeping loft upstairs. With part of the house being two stories tall, the walls on that portion would have been thicker and thus take even longer to complete.

What I've decided to do is to build half of the ground floor in the first phase. Once that half is done, In phase two I'll start adding on the rest of the ground floor, with a loft above that portion. That means the first phase won't need the extra thick walls, shortening my build time.

The first phase will only be about 15' x 15', internal dimensions. It will have a Rumford stove, a nook in the corner for a sink and composting toilet, with built in seating around most of the perimiter, and a large arch leading to the future expansion. This arch will be filled with (plastered) strawbales or light straw-clay until the second phase is done. The roof will be a sloping shed roof, and on the high end I hope to have enough vertical space for a (very) small sleeping loft.

The second phase will be about the same size internally, and will contain kitchen, eating area, larger bathroom and the stairs to the upstairs loft. The loft will probably have a ceiling from 6' at one side up to 8' at the highest point. I will probably build in some closet/storage nooks.

I think I have a chance of completing phase one over the next year, and then take the following two years to complete phase two. This seems like a much more manageable plan - I'm excited!

Hopefully I'll have a sketch or two to post this weekend.

Roof Design Thoughts

I've been contemplating the roof design for my cob house. I really like the roof design of Hilde Dawe's house (pictured here). This roof has a series of roof beams visible beneath the eaves, and in the photo below, which shows the ceiling planks resting on top of these beams.

The eaves are apparently 8-10" thick. I'm assuming that there is a ventilated insulation space of 6-8" under the roof decking. What I'm wondering is just what supports the roof decking? Is there a second set of roof beams hidden inside the insulation space, upon which the roof decking rests?

I like the look of the exposed beams and planking in the loft, and you'd normally look at this design and assume that it is the roof decking you're looking at. But that's clearly not the case here. I wonder if there is some other structure in the insulation space supporting the top roof decking, or if it is in fact another set of beams. Hmm...

Realities pt. 2

So as I intimated in my last post, my idea to build a natural house on this property is a dream that my wife doesn't share. I wonder if I'm asking for trouble to contemplate it without her being more involved?

It's not that she's not supportive of my dream, she is, up to a certain point. But she'd rather us focus on building a retirement home in a place more suited to our eventual retirement. We'd both love a wooded property with rugged rocks and a stream, ideally close to the mountains and in a cooler climate. This doesn't describe Texas, or anyplace we can drive to for a weekend retreat.

But building a home on this property is a dream I've had for at least 30 years, and now that my father has passed the property down, I've been visiting more and have rediscovered my love for it.

So my continued planning must focus on what I can realistically achieve - mostly on my own, although I think my 10 year old son, Jared, will be a big help as well. It may be that rather than a year long project, it is more like two or even three years.

Realities...

This weekend, when I visited my site, I took my wife and kids along. Although my wife has been to the property before (it has been in my family's posession for about 35 years), it was her first visit in over 10 years.


There are a couple of reasons my wife hasn't visited the property in a long time. First, we live about 3 hours away, in a suburb of Fort Worth. Second, my wife is a flight attendant and normally works weekends. Since we've had kids, we just never had or made the time to visit together.

Frankly, my wife isn't completely on board with me making a major investment of time and money on a site that is so far from home. One concern she has is that absentee owner's homes are subject to vandalism and burglary in the area. She has a valid concern - my Dad built a conventional, stick built, cabin on the property shortly after he bought it, and it gets broken into every five years or so.

So what to do? My wife agrees that it is a beautiful property and a good site if you don't consider the distance and insecurity. One notion is to keep construction costs as low as possible - no frills - to lessen the potential loss. There is no way to prevent loss - if someone wants to break in, there is nothing to stop them (nearest neighbor about a mile and a half away). More later as I think this through.

My Candidate Building Site

I visited the property yesterday to do a little trailmaking and site survey. I took this picture of the site I currently favor for my cob house.

This Photo is taken looking SSE (the likely direction the house would face) down a gentle slope. It is a small clearing surrounded by deciduous trees (oaks) and white pine. The soil here is very silty with a lot of very fine sand. But there is a layer of very pure red clay about 16-18 inches down.

I spent an hour or two searching for trees that would make good roof beams for a shed type roof that would span the structure from front to rear - looking for trees that would provide good 20 ft. long poles. I was mainly looking for cedar, and I only found a couple of trees I thought would work - a disappointing result.

The property has been logged in the past, and the pickings are poorer than I'd hoped for. I guess I'm going to have to purchase roof poles.

Design Thoughts

So what am I building?

I've thought about lots of designs for my cob house. From visions of a grand retirement cottage to a small weekend retreat.

In the interests of learning and not biting off more than I can finish given other commitments - work, family, kid's sports seasons, etc., I've decided to start on the smaller side with a small weekend retreat.

I'd like it to at least be big enough to be livable by my wife and I, and our 3 kids, for a week or so at a time. I'm thinking of an open plan first floor containing a large family room, small kitchen & eating area, along with a small bathroom nook and upstairs sleeping loft.

It will be south-facing to capture the winter sun, with no windows on the north side of the house, and only a single window on east and west faces. The south wall will have a series of large windows for solar gain in the winter, and roof overhang should prevent unwanted solar gain during the hot summer months (in Texas, we only have winter for a couple of months, the rest is summer ).

My building site is on 50 acres of deep woods on the edge of the Red River floodplain. It is slightly rolling, mixed woodland. It is far, far off-grid, with no services available. So, it will use a roof catchment system, cistern, pump and filter system to provide potable water. Solar panels and batteries will provide meager electrical power. For grey and black water (sewage) disposal, I am still undecided. The options range from a grey-water dispersal system and composting toilet up to a full blown septic system.