| Owenlea Farm
Nov 14, 2002
Here is a low cost greenhouse type structure that I built at Owenlea Farm. It is 22 feet wide and 48 feet long. The building is made of low cost, locally available materials. It is immensely strong and rigid. It can be built with ordinary farm labor with ordinary farm tools.
It could be adapted for many purposes. For example, this building could enclose 26 Jersey size freestalls with an 8 foot scrape alley. It could be a hay barn to store large squares. It might be a machinery shed, a machine shop, a pit milking parlor or a flat barn parlor.
This particular building has been used for growing flowers and vegetable plants. It has frequently been used for a meeting room and seats over 100 people comfortably.
Plans? You want plans? We haven't got any real plans. But down further is a line drawing.
The large door can be closed in about five minutes with a piece of plastic or canvas and some "wiggle" wire.
The square grate-like things at the top corners of the big door are air intakes. When all the doors are closed, the big fan at the far end runs on a thermostat. When it runs, it pulls air in through the two louvers. I bought the louvers in an auction for a dollar each (or there abouts).
In a pinch, for example if your house blew away in a tornado , you could live in this building. You could also live in it in the high arctic and maybe even on Mars.
Actually NASA's is going to blow away and mine isn't. They don't have theirs fastened down well enough. GRIN!
I backed a tractor in here so you would get a better idea of scale. Up in the loader bucket is my radial arm saw that blew away in the tornado last Sunday.
The material for the 13 bows is native hardwood sawn 1 inch x 4 inches. Oak or ash is fine. This material costs 30 cents per board foot or 10 cents a running foot. Each bow has 36 lineal feet or $3.60 worth of lumber. That works out to 13 bows x $3.60 = about $50.00 of rough native number.
There are 6 planks making up each bow. The verticals are cut 4 feet on the long edge. The other four planks are cut 7' 2" measured on the long edge.
All joints are butt joints. All cuts are 18 degrees.
Two 18 degree cuts butted together make a 36 degree change in direction.
From grade to peak, we have:
(18 + 18 = 36) + (18 + 18 = 36) + 18 = 90 degrees.
This also makes a 4/12 slope from the shoulder to the peak.
In addition each bow has 10 plywood gussets. We can get 24 gussets out of a 4 x 8 sheet of 1/2 inch treated plywood. So there is another $3.00 per bow. Each bow also requires about 1/3 of a tube of glue and exactly 100 square drive screws 1.5 inch to hold it together until the glue sets.
These plywood gussets are the heart of the building. They are 24" x 8" with a 4/12 pitch. The small ends are 4 inches. These gussets are glued with the type of glue that is advertised as for use on "wet, treated, or frozen lumber". The ten square drive screws are ONLY to hold the gussets until the glue sets. They are NOT nearly strong enough to be used without glue!
Each bow is bolted to a ground stake. These ground stakes are rusty old 1.5 inch steel pipe cut 5 feet long. These cost 10 cents per foot at the junk yard. We pounded them in with a hand post driver. They are in the ground at least 3 feet and up to 4 feet depending on the slope. Those are 3/8 inch cariage bolts with 1/2 washers on the wood side.
Here is the inflation fan, which gives the building it's rigidity and a jumper tube to carry air pressure around the corner. There are two layers of plastic film. This is four year plastic. By inflating the space between, we clamp the whole building together with immense force.
If you were to whack this inflated plastic with your hand, it would be about like whacking a piece of 3/4 inch plywood.
Inflation fan. Cost about 50 dollars.
Here is some "wiggle" wire track and some "wiggle wire". This is how we fasten the double plastic film skin to the building.
Closer picture of wiggle wire.
Here is the outside bottom corner showing two layers of plastic clamped onto the building with "wiggle" wire.
Here is another way to fasten plastic film to a greenhouse structure. The black stuff is agriculture "drip" line used for irrigation. It's tough. This batten material is stapled on with a staple gun using 5/8 inch staples about 1/4 inch apart.
The end braces are important for rigidity.
Here is the floor material. It's standard nursery ground cover. This stuff never wears out. What you see has been outside in the weather here at Owenlea Farm for 5 years. We have it fastened down with "landscape timber" spikes but it's cheaper to make giant staples with 5/16 steel rod.
Here is the fan. I bought a truck load of these in an auction. I sold most of them and more than paid for this greenhouse.
These are common and cheap, as greenhouse operators go broke even faster than dairy farmers! And for the same reason. They have got to expand so they can pay for the last time they expanded!
The fan came with a three phase motor. But one of the neighbors, who doesn't have electricity, had just bought a fancy Delta table saw with this motor on it. I bought it at a good price. It was the wrong speed for the pulleys that we had, so we put in the jackshaft (middle).
Outside looking through the fan. Louvers are open but shut from gravity when fan is not running.
The fan box on the north end of the structure.
A door. This has a double layer of plastic and cost next to nothing to build.
Make sure the door has clearance and opens inward because of snow.
It's just common 2x4's that are notched a little bit.
More door detail.
Here is how we built the threshold.
And that's it.
Thanks for visiting Owenlea Farm.
I believe greenhouse structures are an essential ingredient in Low Cost Structure dairy farming.
I'll go the extra mile to explain details on how to adapt this to your specific dairy farm application.
I think you could go up to 30 x 96 with this design. It would be simple to set this on a poured concrete wall about 4 feet high.