I'm looking for inspiration, thoughts and advice for my first cob structure (first structure ever planned and built myself).
This is my first attempt at playing with cob. At the moment it remains a thought experiment, that is until I can get my hands on some clay. I would very much like to build it this summer, but life and lack of clay may get in the way.
The theory is to start small. Building a garden wall, to me, would be like teaching someone to knit by making a scarf. Once they've knit the first foot or so, they've learnt all they can from that project and get put off the craft with the pressure of finishing their first real project. Something smaller with more complex learning is the thing for me.
So, I'm going to build a goat house.
The requirements for my goat house:
-low enough at one point that the goat can jump on the roof and use it for goat play
-strong enough to withstand both goat and sheep
-provide wind and rain shelter -MUST HAVE GOOD AIRFLOW for health of animals and my own personal sanity - ie small windows.
-well hidden from casual prying eyes
Things I hope to learn:
-how to make cob -how to make foundation
-how to make windows (open, no glass) in cob
-how to make roof
-how to make living roof
-find some good idea for the floor and learn how to make it
-how this kind of construction stands up to sheep and goats (if it can survive those two critter types, it can survive any seismic activity)
-how to harvest natural materials and use them
Hopefully, what I learn from this project, I can apply to larger cob building endeavours in the future.
The interior space will be roughly 4'x4' square, or 5' across circle. At the most, 5 foot tall (inside) with at least part of the roof 3 foot high or lower. The place I want to build it is sloped, so I imagine the uphill side will be where the roof is lowest and the goat can jump up.
Financial resources: non-existent.
I have an idea in my mind of what shape it's going to be, but before I share, I was wondering what more experienced builders could tell me about this project.
-What shape would YOU build it?
-How wide would the foundations be if you were making this?
-What added considerations are needed for goat and sheep proofing this building? Goats climb, sheep rub against things, about (our) knee hight, and rams... well, they ram things. Rams will probably not be in that pasture.
-If you could only recommend one book/website/resource for building with cob, what would it be? What makes that particular resource so great?
-Is it possible to build a living roof without a plastic membrane, or is it going to be like the old soddy roofs - rain outside one day, rain inside three days later.
I don't have a lot of personal finished product experience but I think I learned a lot from Ianto's cob cottages this last fall. Old broken concrete makes an awesome foundation and floor or you can fill it with packed gravel. Cob will make a decent flooring, finished with oil is amazingly solid. Your size is reasonable for a first project, They were working on a 60' X 6' wall while I was there, Great guys.
Don't forget to poke drying holes in your walls and aim for 9-12" thick, fill the drying holes after the other cob has dried. Block in your windows and let the cob dry and then knock out the blocking. A header 6" wider on each side of the window should be enough. Need a drawing let me know.
For an animal house you might consider 2" vents @ 6" off the ground and another set just below the roof allowing for a good exchange of air in warm weather that you can easily block the bottom from the outside in the winter.
From what I've seen I would do a pond liner or a couple layers of thick black plastic for a roof liner. I don't like these materials in general but I think if we use them in a responsible and intentionally long lived manner it's appropriate. They're long lived, they don't degrade easily and they will work well for a roof, it's too bad anyone makes them at all and I hate feeding the market but my use will be sustainable.
Building small is a great way to learn and not get discouraged by the size of the project. And these are just my opinions and suggestions.
I would build any earthen structure no less than 18" thick. But probably thicker if its going to hold a living roof AND animals. Foundation depth should go down to at least your areas frost depth if not a little deeper. Foundation thickness should be at least 2X as wide as your walls thickness. So if you build a 18" thick cob wall. your foundation should be 36" thick, 9" wider on each side of your cob wall. I would also start my cob walls at least 18" above the ground, built on top of stone, brick, urbanite ect. Anything that will keep your cob walls far away from any possible ground water.
Is the ground not a good enough place for goat play? The structure will need to be fairly robust in order to accommodate living roof and animals safely.
The less 90 degree corners your structure has the better it will stand up to seismic activity. Im not too familiar with the habits of goats and sheep, but the structure should hold up to them just fine.
I would look to vernacular roofs of your region to find something that works there.
And since financial resources are non-existent you'll have to use what's in your immediate vicinity to build with, which may end up not being cob. So in that respect be flexible and use whatever you have available. Whatever you have on your property, whatever you can go and scavenge, don't limit yourself! There is a plethora of building material everywhere, you just have to be open to see it. Whenever I see an abandoned pile of tires, I see a wall. Whenever I see discarded piles of concrete I see a rubble trench foundation or a stem wall or infill for cob walls. A dead tree is a roof support or milled down is siding or a door ect ect. It doesn't end. There are plenty of materials out there that people have deemed garbage. But just because they no longer are usable for there intended purpose doesn't mean they don't have a purpose for something else.
Stay where you are, work with what you have, do what you can
Goats need structures to climb on as climbing is part of their basic goat nature. Without it they get depressed and a depressed goat is not a happy goat - those with goats will know what I mean.
It seems silly to me to have both a shelter and then build playthings for them to climb and jump on. Especially since they will climb on any shelter I make anyway.
Thankfully I have small goats. Max weight SHOULD be 150 lbs per goat, and max number of goats SHOULD be four. That's 600 pounds of goat if they all get on top - is that a lot for a roof?
Thanks for the link to the book. I just picked it up from the library today What timing.
The frost seldom goes more than an inch deep, but I've seen it up to three inches. So what do you think of a foot deep foundation? 100 years ago, the winter was much harder, so maybe I should go two feet deep to take climate change possibilities into account? What's a usual depth for people who get normal winters?
We have a month or more before the rainy season stops, so I'll keep researching and imagining different shapes for the structure. I found a bit of clay, and hope to pick up some more soon.
Multifunctioning the structure as a shelter and goat play structure is a great idea. No, 600 pounds is not a lot of additional weight as long as the roof is built to accommodate the additional load. Plus if its a living roof you'll have to take into account the additional soil, and when it rains that soil will absorb a lot of moisture making for a lot of extra weight. Even though it is a small space, the roof will still need to be fairly robust. But I am no engineer, so cannot help in exactly how "robust" the roof should be. I'm sure searching around and reading info on living roofs will give you a good idea of how to build one without the risk of it collapsing.
I know our environments are very diverse from each other, but even here in the great basin desert, frost levels in the soil can reach 18" below ground level. In the northeastern US frost levels can reach 5'. Do you receive snow? If so I would guess that the frost level depth in your area to be near 2', but that is a very poor guess at best as I have no clue about your environment other than you are probably in a temperate tropical zone. Still that being said and not knowing anything of your soils bearing capacity, I would still dig my foundation to be as deep as my cob walls are wide. So if you decide on building 18" thick cob walls, I would make my foundation 18" below ground level.
Stay where you are, work with what you have, do what you can