Melissa Sullivan

Hi!
I'm in Coconino County too, and while I don't really have answers to your questions, the sustainability dept was really helpful to me a few months ago when I was trying to figure out how to get around the rules for building a 300-400ft2 greenhouse with a cob/earthbag north wall without a permit. Unfortunately, they were great at getting me the answers I needed from other departments but were not helpful in avoiding permits . They seemed to actually be interested in finding workarounds to make my project happen but did not mention the program you're talking about (I'm also AR with 1 acre, in Parks). So, I had to stick with a 200ft2 build to avoid it the hassle.
Keep us posted, I'm really interested in hearing about your progress.

I don't think these are Coulter pine cones. Coulter cones are painful to hold in your hand- they are covered with large  prickles. They're also very beefy looking and extremely heavy.

I'm not sure what they are, though! Try looking up Jeffrey Pine cones. They can get as large as what you have pictured, and they don't hurt your hands when picked up (the prickles face inward). They grow in higher, wetter mountainous habitats than Coulter.

Thanks all - I really appreciate the feedback, and one of these days I hope to answer more questions than I ask!

Yes, with my clay soil I'm very conscious of drainage and doing the foundation right. Thanks for the explanation of the redundancies and I'll put the drain pipe in - especially since I have it anyway.

I am in the process of digging a rubble trench foundation for a greenhouse which will have an earthbag stemwall and north wall to act as thermal mass.
I will be digging the trench 18" deep, lining it with fabric to prevent silting, filling it with 1" scoria, and starting my first row of earthbags below ground. I have clay soil, and I am digging a ditch from the foundation to lower ground to aid drainage.

I just bought a roll of 3" perforated drain pipe to run along the bottom, because that's what my research on rubble trench foundations has indicated that I should do. But I'm looking at this stuff and have two concerns: 1) won't this get crushed with the weight sitting on top of it? and 2) why do I need to do this if I'm already filling the trench with rock and am sloping it to ensure water drainage? What additional purpose does the drain pipe serve?

Thank you. I wish their blog had an update on how the cobwood hut is faring, beyond the initial build!

I appreciate the multitude of reasons they felt that going with straight cob would have been easier, though several of them don't apply to me (I have an unlimited supply of wood) but I will keep it in mind.

I think I will make a mini cobwood test wall and see how it fares this winter, and I'll ensure it's in the sun and gets the full range of daily temperature swings.

I may have missed when you usually get rain, but your climate sounds a bit similar to mine. I was also plagued with hot days and cold nights all summer, which few plants do well in.

I second the turnip recommendation, and would also add beets, onions, and potatoes to your list. The onions may eventually bolt if they don't get enough water. If you have enough water to grow tomato plants, then these should work. I've also had success with wheat, which just thrived in oppressive heat and just a few rain events.

I also *highly* recommend shade cloth for leafy greens if you're in an area that gets a lot of sun. I use 30% shade cloth (i'm at a high elevation too, so the sun is extra intense) and helps immensely, especially when the plants are young.

William Bronson wrote:I think the hot moist environment of a greenhouse could wreak havoc on any kind of structure that included cob.
I have also heard keeping cobwood walls sealed  is difficult, as the wood and cob expand and contract at different rates.
Finally, cob structures need a good roof overhang, something not usually built into a greenhouse.

All that being said, a cobwood wall could offer a lot of mass.
So if you have one on a proper foundation of stone, maybe cover it in plastic on the southside and build your greenhouse against it.
Bring that same plastic sheet over the top of the wall to become the roof of a canopy, so the wall is open to the air, but protected from precipitation and you can extend the canopy as much as you like to form a place for drying firewood , for instance.

Thank you for your thoughts! This was really helpful and echoed some of our concerns as well. We were planning a substantial roof anyway, and something key to the design would be to ensure that condensation forming on the inside of the roof drains away from the cob wall. I was wondering about the effects of humidity, but I also need to check with people around my area to see if their greenhouses even get that humid. Our climate is so dry that it is hard to imagine a situation where humidity actually becomes a problem, unless I happen to build a particularly airtight structure.

Would a cordwood wall with just cement mortar perform better, as far as sealing goes? Or same problem?

Hi,
I am wanting to build a 300-400 ft2 passive greenhouse, and I'd love some insight.

I am at 7300' in northern Arizona, so I get a ton of sunshine, wind, and large daily temperature swings. Winters are in the teens at night and 30s-50s in the day. Summers are 40s at night and 80s during the day. Along with extending my growing season, I want to create a space where I can moderate the large temperature swings.

My land is flat and at the bottom of a bowl. I have 6" of beautiful loamy soil and then it's pure red clay. No rocks. Because of this, we get some flooding each spring along with snowmelt. By "flooding", I mean places with standing water, deep mud, and water flowing through all the gopher tunnels that plague my yard. This is more a result of the impermeable clay soil than the water table actually getting this high. Either way - I don't think a walipini is a good option at this site.

Here are my questions, and I'd appreciate to hear thoughts on this!
1. What foundation issues do I need to consider? My county considers the frostline at 30" depth, but with the clay and the seasonal water saturation, is this going to be a problem?

2. Given the local, abundant resources, I was thinking of making a cobwood north wall to provide insulation and thermal mass. Obviously I have all the pure clay I want, and there are huge piles of Ponderosa Pine from all the forest service thinning projects. However, I have found 0 examples of greenhouses made from cobwood. There must be a reason for this - is this a bad idea?

Stacy Witscher wrote:I've tried them with no luck. The techniques that worked best for me are putting gopher wire in the bottom of my beds and pouring down into their holes a mix of water, castor oil, garlic and chile peppers.

Thank you. Do you remember which brand you tried and what type of soil you have?
I have not had luck with castor oil (but haven't tried the mixture you recommended), and gopher wire is not an option. I am debating on renting a trench digger and burying gopher wire 2' deep, but I really don't want to!

I've been searching around for gopher control ideas that I haven't tried yet, and was wondering if anyone had any experience with those solar-powered ultrasonic spikes that emit an irritating sound underground? I found a thread discussing the battery powered ones (didn't work for this person), but it was an old thread and I am wondering if these have improved at all. The reviews on Amazon seem to be good, at least for some brands.

If not, I may just buy them and write up my experience here.