In starting to look at the factors in building a greenhouse, there are several factors to consider that I’ve learned in building more than a dozen greenhouses over the years.
Level The Ground
All the books say you have to build your greenhouse on level ground. And for the most part, this is superb advice. My first one (only 1500 square feet) was constructed into the side of a hill but the structure was level. I brought tons of fill in to make the outside level and shore up the concrete blocks I used for a foundation.
My First Greenhouse Was A Killer
This was my big solar greenhouse, a Brace Institute design with a solid north wall and then I sunk it into the ground and filled the “basement” with large rocks laced with air tubes for a heat sink (another story but it didn’t work very well) This was a pricey option but a good one for a propagation house – light levels were too low for producing anything other than bedding plants
My Second Set of Greenhouses
For my second set of greenhouses, I got smart and leveled out the ground first with a bulldozer. Then I built the next 5 greenhouses on level ground as you’re supposed to do. These worked out well although they were traditional steel hoop houses covered with plastic
The Third Phase and I Regret Having A Hilly Farm
The third and final commercial sized range went onto another hillside. I didn’t level this one but built 4 houses up and down the slope. These houses were only used in the late spring for bedding plants (and no year round growing) so I didn’t think the costs of leveling the ground were warranted.
There’s good news and bad news here. The slope creates a serious temperature differential between the upper and lower ends. You have to pump your heated air down the length of the greenhouse to the bottom of the slope allowing it to rise naturally upslope.
This demanded a heat vent (plastic sheeting) on both large furnaces plus another fan running to circulate the air within the houses. Normally, I’d only have the furnaces pumping hot air and use those two vents to both heat and circulate. Trying to do that on a slope didn’t work and I had to have the third fan running constantly to keep the temperature constant.
On the other hand, we got very good at putting crops that liked cooler air at the bottoms of these big houses (3000 square feet each) so that was a bonus.
Level is better
Ground deep enough to anchor
It is surprising to many folks how easy it is for a greenhouse to blow away in a big wind. The next time you see a greenhouse, imagine it’s an airplane wing rather than a greenhouse and when the wind blows across the top of it, all that plastic wants to “lift” up.
So it has to be well anchored if you want to build a greenhouse properly.
Oe one of my houses, the rock was very close to the surface 🙂 and I drilled holes in the rock with a big rented compressor and air-drill. Then I sunk the foundation pipes into those holes, cementing them in.
You can’t be too careful with this size of plastic (100-feet x 40-feet) or it will easily wrap itself around the nearest tree (even if the tree is several miles away)
I learned this hard way when I moved to our very windy island. I installed a quick, plastic garage (one of the tubular steel covered with plastic types) and thought I had anchored it quite well.
Faint chance. It did indeed pick up, wrapping itself plastic and all, around the nearest downwind tree.
Forewarned is forearmed
- The real thing here if you’ve read all of the above is that I’ve spent different amounts of money over the years levelling and making sure the anchoring is right.
- And doing it right does indeed cost money.
- So when you’re figuring out the costs to build your greenhouse, let me suggest you take a good look at your foundation anchoring and levelling.
- Because when it comes to building a greenhouse, there’s only one right way.