How To: build a Geodesic Chook Dome - Milkwood: permaculture courses, skills + stories - Eco Supplements

How To: build a Geodesic Chook Dome – Milkwood: permaculture courses, skills + stories

Maybe you’re already familiar with that classic Permaculture tool known as the Chicken Tractor / Chook Dome system. No? Awright – in a nutshell: In this context, a Chicken Tractor is any structure that can be moved from place to place in a garden with a bunch of chickens housed in it.

The chickens living in the tractor do what chickens are so good at: scratching up the soil and turning it over, making short work of any greenstuff to be found, and spreading their manure the length and breadth of the space available to them (not to mention producing eggs and more chickens).

Establishing the Top Food Forest at Milkwood, thanks in part to the Geodesic Chook Dome.

By moving the tractor regularly you are left with a series of spaces for garden beds each the shape of the tractor, and each with the soil nicely prepared, the weeds and grass all pecked out, and a goodly amount of chook poo thoughtfully spread.

Mulch each new area heavily, and plant away – a great way to start a vegie patch, or a food forest.

Linda Woodrow, in her very fine book The Permaculture Home Garden, outlines a chicken tractor system based on a thing she called a Chook Dome, which is basically a hemispherical chicken tractor.

Chook Domes are great because two people can move them easily, the structure is reasonably strong, you can build them out of readily available materials, and you end up with circular beds – great for guild planting, and a more efficient use of space than say a rectangular bed.

A Chook Dome of the classic Woodrow design

The only real downside to the original Chook Dome design is that the structure isn’t particularly strong, usually takes two people to move, and needs to be replaced occasionally because the stress on the joints sometimes causes the whole thing to collapse.

Enter an improvisation upon the theme by a fella named Robert Freeman: The Geodesic Chook Dome.

The Geodesic Chook Dome has a couple of huge improvements on the Woodrow design: being essentially a geodesic structure, it is much stronger, and the stress is distributed more equally across the structure.

This means that ONE person can move it easily by standing inside the middle, lifting up and trotting off without the whole thing coming to grief. However, unlike a traditional geodesic dome (a la Buckminster fuller), which is composed of many triangles and therefore lots of joins, Freeman’s design is composed of long, curving struts which criss-cross the form and are anchored to the base.

This means there are essentially no bits that can break off, as all the joins are around the circular base at equidistant points, which again distributes the stress and makes for a very strong yet flexible structure.Anyone with a bit of a thing for Geodesic Domes should be impressed with the elegance of Freeman’s design, I think. Geodesic domes are also dear to my heart, as I used the form once in a certain art project.

It all sounds a bit complex, I know – but it’s really not that bad. Think of it as a great big garden puzzle that will increase your garden’s fertility a hundred-fold. What’s not to like?

We found Robert Freeman’s plans online 2 years ago, and now our top food forest is slowly being established thanks to one of these structures. Our particular Geodesic Chook Dome houses an average of 6 chooks and 1 rooster.

We put in one nesting box made from the grass-collector of a lawn mower (great shape, strong, warm and you can get them at the dump) and perches for roosting.

For durability, we clad ours in scrap chicken wire rather than netting.The dome is surrounded with a ‘skirt’ of chicken wire about 30cm wide laid flat on the ground, which is held down with rocks.

This ‘skirt’ has been sufficient to prevent foxes or anything else digging their way under and into the Chook Dome, which is pretty good considering we are housed at least 500m away, well out of earshot and scent range.

Nick inside a completed Geodesic Chook Dome – note the strength of the shape when lifted – no distortion or weak points…

Each time we move the dome, it gets pegged down with tent pegs hooked over the circular base. For shelter we have a large tarpaulin which is pegged down over the dome separately. This is an important point – always make the shelter sheet for your Chook Dome a SEPARATE PEG DOWN AFFAIR from the actual dome. A dome with a shelter sheet either attached or incorporated is, in fact, a large, very effective kite.

We rotate our Dome every two weeks-ish and a couple of days before we move it, we drop in a bale of lucerne hay through the door. The chooks think this is Christmas and love scratching up the hay and spreading it all around their dome. It’s a free mulching service! Thanks chookys.

Our dome ended up being about 3m wide at the base, about 1.6m high at the apex inside, and can be lifted comfortably by Nick or lifted uncomfortably (but it’s quite possible) by me. To lift and move it, Nick just stands inside at the apex, lifts up with his hands, and off he goes.

I keep an eye on the chooks and herd them back in once the dome has come to its next resting place (a handful of scratch mix or some tasty greens always helps to get them back in). Ours has been running about 18 months at time of writing, and is as sturdy as the day it was born.

Robert Freeman has very kindly invited us to host the calculations for his fabulous design here at Milkwood.net, so see below and feel free to get cracking.diagram dome

Plans and calculations to build your own Geodesic Chook Dome, by Robert Freeman:

1. Choose the size of dome you want: These instructions are for a 3/8 sphere. If I remember correctly, a 10-pipe dome is approximately the same size as described in Linda Woodrow’s book. I used white PVC piping, but perhaps 3/4 inch rural grade poly pipe might be rigid enough to work. It would be a lot cheaper I guess.
Total number of 6m lengths

9.00

10.00

11.00

12.00

13.00

14.00

15.00

16.00

Total length of pipe (m)

54.00

60.00

66.00

72.00

78.00

84.00

90.00

96.00

Area of chook yard (m2)

9.49

11.71

14.17

16.87

19.80

22.96

26.36

29.99

2. Join the pipe together and cut the lengths you need (meters). You won’t need any joiners if you measure your cut from the end without the bell, and make the circle last. Join the pipes with special blue solvent glue you can get at the place you got your pipes.
Circumference of base circle (1 of these)

10.92

12.13

13.35

14.56

15.77

16.99

18.20

19.41

Length of Big arc (5 of these)

4.84

5.38

5.91

6.45

6.99

7.53

8.06

8.60

Length of Small arc (5 of these)

3.78

4.20

4.62

5.04

5.46

5.88

6.30

6.72

3. Use these sizes in Step 4 (these are the sizes of the sides of the triangles in the dome)
B–B (m)

0.47

0.52

0.58

0.63

0.68

0.73

0.78

0.84

B–R (m)

0.56

0.62

0.69

0.75

0.81

0.87

0.94

1.00

R–R (m)

0.59

0.66

0.72

0.79

0.85

0.92

0.98

1.05

4. Mark where the pipes will cross (the apexes of the triangles–where two pipes cross will have a mark of the same colour. I use a blue and red marker). B-B is the length of the space between 2 blue marks; R-R is the length of the space between 2 red marks; and R-B (or B-R) is the length of the space between a red and a blue mark as given in step 3, above. The first and last marks are at the end of each length of pipe
Big arcs B-B-R-R-B-B-R-R-B-B
Small arcs R-B-B-R-R-B-B-R
Circle B-R-R-B-B-R-R-B-B-R-R-B-B-R-R-B-B-R-R-B
5. Assemble your dome To avoid crimping the pipe, start by making a pentagon fastened* at the blue points in the centre of the 5 big arcs. (Before fastening, weave the big arcs over and under each other.) Stand this up inside the circle. Check that the big arcs continue the over-and-under pattern where they cross each other at the red points. Now fasten the ends of the big arcs to the base circle at the appropriate blue points (I found it easier to put all the ends on the inside of the circle, although this does upset the over-and-under pattern). Fasten where the red points of the big arcs cross (Sometimes errors creep in when measuring, so even out any odd places and fasten where the pipes want to cross—it’ll be close to the red marks). The dome should now be quite stable. Weave in the small arcs, keeping the over-and-under pattern. Fasten temporarily until you have them all in place. That way you can even out any slight measurement errors.* I fastened where the pipes crossed by drilling a small hole through both pipes and tying them together with a piece of wire. Perhaps you could use cable ties; these are cheap, strong and easy. And if you don’t like your dome, you can still use the pipe. I’m going to use these in my next dome.
6. Clad your dome with chook netting: Making the dome was the fun part. Cladding is not so easy, but the chooks aren’t fussy about appearance so be inventive.
7. Peg your dome to the ground! Plastic pipe is great: it’s easy to work and lightweight, but it can make a great kite in only a moderate wind. The pipes are flexible and don’t break easily, but the joints are quite rigid (and also maybe the glue weakens the plastic?). When I found the first of these domes blown into a tree, it was fine except for 3 clean breaks right at the joints. So the moral of the story is: Peg it down.

 

Thanks Robert! And it’s worth noting that this design works well on a variety of scales – I’m looking forward to building a mini version (1.2m across) for our raised beds in our vege-garden-to-be at Milkwood this coming spring…

 

Nick showing Joel Salatin our dome in December 2010 (same dome, still going strong).

** 2011/02 update: Just a note to say that the geodesic chook dome is still going strong and structurally sound 2 years later! And still being moved every 2 weeks or so, as our top food forest crawls slowly across the landscape.

We even recently showed our dome to Joel Salatin during his visit to Milkwood Farm. Joel’s polite but subdued interest could be due to the fact that his eggmobile and pastured poultry systems are a little more advanced than ours! Never mind – we love it, and it’s doing a great job for what it is. We’re looking forward to building more!

***2013 update – Richard, who commented below – sent through a helpful picture to help future geodesic chook dome builders:

geodesic chicken dome diagram