first of all: english is not my mother languaje and i do my best in writing correctly but it will be many mistakes, please forgive them.
this project is about a 40 square meters automatic drip watering greenhouse for producing the main ingredients (indeed, everything but the salt, the olive oil and the vinegar) for making the world famous andalousian cold soup named Gazpacho. You can find recipes of it with ease; tasting the real thing is a different matter.
The actual machine that you will need for blend togheter all the ingredients can be found in any kitchen and is out of the cover of this instructable.
This project is also a way to get some first hand experience on strawbale / mud construction without the assle of getting permisions, fitting into building codes, etc, and at a very small fraction of the cost. The greenhouse was, and will be, the perfect excuse for building illegal legally (or something). If you get too weird in your experiment you can always claim an artistic nature, stating your effort as an sculpture. It is amazing what you must do in the "first world" for bringing back architecture to the hands of the people.
Two factor were criticals in here: water and money.
In my case, water must to be pumped from a nearby spring to a gravity tank for giving presure to the system. A full tank of 1000 liters must be enough for at least a week in the full heat of the summer, so it defenitly needs some kind of automatism for make it last enough.
This ghouse was made in Spain and in 2010 at a total cost of parts about 300€
-100€ for the plastic sheet (100square meters)
-50€ for the strawbales (very good price from a friend, maybe doubles in the complex straw market))
-50€ for the iron electronet (the kind used for concrete reinforcement in flooring)
-100€ on gas for the van to carry materials and on misc hardware.
-the wooden acacia structure was for free (for the cost of getting there with a chainsaw and cut the parasite trees)
-the plastic tubbing for the roofing structure was recicled from pieces of a optic fiber conduit found in the road. So are the door, the water tank and the parts of the irrigation system.
-an estimation of time would be around a week x 2 workers without killing yourself.
The site was a piece of unused agriculture land that i plan to convert soon (now) in a permaculture garden food forest, but this will be another instructable (a long one: such food forest takes 5-7 years to stablish, but then lasts forever by itself)
Step 1: Materials and Tools
-wood for structure
-secondary structure in iron wire, bambú or plastic tubing
-clay rich mud
-plastic sheeting for greenhouse
-iron electronet (the kind used for concrete reinforcement in flooring)
-some chicken wire
-an old door with frame
-water supply and drip irrigation system
it does not make much sense a real list of parts due to the recycling aim behind this project: use wathever you have handy.
you will also need
-a way to get the stuff on site ( in my case a brave old Citroen C15 Diesel van with +600.000 kms)
-the usual gear for earth construction: weelbarrow, shovel, ladder...
-electric drill, hand tools
-help (for setting the structure in place and putting the strawbales in the upper rows)
Step 2: Structure
I used free acacia trees that where parasiting an piece of land nearby. I asked for permision for cleaning a few of the biggest ones and everybody was happy with the deal (except the trees themselves, i ma afraid).
The construction must be removable and the wood reusable. Also, i want a easy way to mount and demount so y used natural U shaped trunks buried in the land for suporting the beams. They got conected by means of pieces of 16mm threaded rod, flanger washers, and locking nuts.
All you want is an structure for:
a/ a vertical north wall
b/a curved shape for the roof and the south side
c/2 laterals sides, one with a door, the other one with means to get the plastic sheet fully open for cooling.
so if you have bamboo available use it, if you have scrap iron from a construction site use it. if, like me, you have access to a uncontroled forest clean it and use the scrap.
Creativity is the key.
Step 3: Roofing / Plastic-sheet Structure
I made it from conduit for optic fiber but it can be made out of anything long and stiff like cane, bamboo, iron electrowire...
Make a profile curve insert in the shape or your main structure. Do the ones in the laterals, then the middle one, get a rope and a level and get a upper line for all the rest.
In my case, i made a long thin beam on top of the lateral columns to provide me a bending point for the conduit ribs. Of course the pieces that i found where'nt long enough so i made conection pegs out of hardwood and screw them togheter. I got those lenghts custom cut to fit the lower side of the main structure (of couse all of them are slightly differents because of the irregularities of found logs, but as far as they bend at the top in the same point an make the same shape it will be ok). They got connected to the main wooden structure by means of pieces of ribar, cutted in angle for easy nailing and hammered in predrilled holes in the trunks. I got one rib each 40 cms or so.
Then i set transversal reinforcements out of cane (free, close to the river). I set the canes about each 40 cms aprox. tying them against the conduit ribs with packaging tape. One of the best things of this way of building is that you are guessing the measures all the time but can actually leave the tape measure in the box. It can be all eye-bowled. Exact measurements are not very helpful when you are working with raw natural materials.
Step 4: Strawbale Wall
Use some rope for alignment and leveling purposes. Following the rope make a foundation about 25 cm or so for leveling your wall and provide some isolation from wetness of the land. Set some big rocks in the corners of both ends for prevent damage.
Get a plastic sheet over the foundation and start setting strawbales in place.
I stopt after 5 rows, waiting for the roof plastic-sheet and then putting the 6th row of strawbales on top of the plastic. But not yet.
I also leave a hollow for a window for ventilation and wiev purposes.
Prepair the mud. I was trying to be as fast as possible and i toke the wet mud straight as it was on site, so a lot of small stones, roten pieces of wood, bugs and stuff like that got incorporated into the wall. No big deal. Just get a weelbarrow full of that rich clay, add some water, scramble 5 minutes with the showel, wait 5 minutes, scramble again and ready. Probably a bit of sand in the mix will help with craking issues but it was none available so i skeep it. I got some chiken wire attached to the wooden structure to reinforce the outer side and some straw mixed with the mud in the inside just to test the differences overtime. The next wall will be without chikenwire, straw in both sides is more than enough.
So mix the mud with some wet straw right in the wheelbarrow, not too much.
Plaster everything by shooting handfuls of mud in to the wall.
Sculpt the wall if desired. Invite friends. Have great fun.
Step 5: Closing
Set the electrowire walls to hold the plastic laterally. Since the plastic conduit ends in the structure and not in the floor we need also cover this lower part. I used more electrowire for that, atached to some pieces of curved reebar buried in the floor and fastened to the wooden structure.
You can do it entirely with the material that you used for the plastic structure, forming a big basket. Again, it depends on what you have handy.
Then it is time for the plastic sheet. I used a long piece of pipe to hold it straight and then just traveled into final position. The sheet should be big enough for cover the 5th row of strawbales and all the plastic structure, leaving an extra meter for wrapping around a thin long wood and getting buried for windproof seal. Use zipties for secure it in place against the lateral ribs.
Set the last row of strawbales on top of the plastic. Mud plaster them. This row will get wet and will make a nice compost in one or two years. In any case the plastic will last only one year so they must to be removed for setting a new one.anyway.
Wrap the plastic around the lateral sides. Make one cut for the door and attach plastic to the frame. The oposite lateral plastic wall must to be removable for ventilation, so a current can flow from or to the door. I used a long piece of wood for wrapping around the plastic, oppening that way the whole wall.
Step 6: Preparing the Soil / Irrigation System
Time for setting the drip irrigation system wich is just pretty straight forward plumbing. We set a irrigation timer for dosing the water along the week.
Step 7: Growing
Next year will be fewer plants and more variety.
The whole thing works as a heat and water trap.
Really hot temperatures can be reach and you must be aware of that and ready for open it for vent quickly if you not want to cook the tomatos alive. Next year i want to set a sensor and a motorized flap to open a vent when needed. Actually, the idea includes a solar panel on top of the watertank tower and a battery bank for power a temperature/soil wetness/air humidity sensor grid and some actuators for watering and venting on demand of the circunmstances, automatizing the whole process. Hence the title of this instructable.
The north wall, the straw and mud experiment, works great as a cold wind stopper and the mud (more than 20 wheelbarrows full of clay in the inside layer) and the land itself holds a good deal of insulated heat, releasing it along the night. With outer temperatures as low as -8ºC inside never was under 0º, according with my cheap highs and lows thermometer, so no antifrozen night stowes needed. When fully closed it also forms a very humid environment wich is great for the early stages of the plants. It is the perfect spot for baby pot plants, seedlings and cut cloning.
We (I, the builder, and my friend, the greenhands) are very happy in general with the performance of the thing.
PD: if some of this text makes no sense please let me know and i will fix it (if possible).
thanks for reading