Mini hoophouse construction question

17 years ago

I'm considering all of the details in the construction of a mini hoophouse. I have 2 beds, each 2' wide and 10' long. I have plans to put sweet potatoes in those beds. They are presently covered with black plastic in order to get the soil warm enough to plant. After planting, I want to cover the plants with hoophouses in order to keep the heat high enough to have the sweet potatoes succeed in this zone. I've started my research to successfully construct these structures.

My initial plan is to anchor 4 hoops for the 10' bed length, equal distant apart. (The hoophouse will be 4' wide to cover the bed and still have some "fudge room" on each side- just in case!) Any recommendations for what to use for hoops? Checking prices, I'm leaning toward water pipe that comes in a roll. But what thickness would be best? I don't want to waste money on something that will not be strong enough to do the job, but don't want to spend money unnecessarily. It seems that there are two... pressure levels? 100 or 160 psi. Is the 160 psi more rigid. and would thus provide more support? Or will the 100 psi be more than sufficient? For 100' in the 1" thickness, the 160 psi will cost twice as much as 100 psi ($50.00 as oppposed to $27.00). For 100' in the 3/4" thickness, the cost is $32.00 (160 psi), or $21.00 (100 psi). Which would be preferable? As an aside, if this project is successful, I will keep the structures to try to use as cold frames throughout the winter.

Now the plastic. DW recommends just buying regular 6 mil plastic to start, instead of making the initial investment in greenhouse plastic. The price difference appears to be substantial. I am leaning towards regular plastic until we see if all this succeeds! In the back of my mind I have already started planning for a full size greenhouse structure (maybe in a couple of years) so all of this learning will help for that as well.

Any suggestions will be greatly appreciated.

Rob Mac

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Comments (4)

chuck60
17 years ago
Rob,

First, why do you need to cover the sweet potatoes? I guess if you want to start them earlier than the suggested planting date for your zone it might make sense, but I have no problem growing sweet potatoes here without protection.

Secondly, I don't think you want to use the flexible water line. PVC water pipe works great and is really cheap. Plus, there are connectors you can get to make all kinds of shapes with it. If you want a really long lasting structure, you can also go to metal pipe. There's a thread here somewhere about a bend-it-yourself jig that makes building metal pipe hoop houses very affordable.

Chuck
trianglejohn
17 years ago
I'm not sure my experience will help you out - I build a pvc pipe hoophouse in the garden each winter to store large potted tropicals in and to keep the squirrels out of my potted bulbs. I've bought greenhouse plastic and used 6 mil plastic sheeting from Home Depot. I prefer the plastic sheeting because it doesn't allow much light in, it allows the heat in but it is kinda milky and seems to act as a filter for bright sunshine. I am trying to keep things asleep in my structure. I am not trying to grow anything. The 6 mil plastic sheeting is cheaper but I doubt it will give you the intensity of light you want to grow sweet potatoes - they seem to like it hot and full sun.
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robbiemac
Original Author
17 years ago
Chuck- This is my first year veggie gardening seriously. All I know about sweet potatoes is that they are a hot weather crop, mostly grown in the south, but can be grown further north. (And that they are very good eating!) I don't know where that puts me as far as my location goes. I was figuring that the more heat I could generate early in the season, the greater chance of success. Most of my knowlege base is coming from what I am reading on line- not any real life experience. But that was the reasoning behind the hoophouse idea. The beds that I will be using for them is in full sun.

I might be okay without any plastic?
sfallen2002
17 years ago
I found that PVC pipe over rebar worked pretty swell. My house was ~14' wide, maybe 5'-6" tall at the top of the hoop. I ran one pipe down the center of the roof as a purlin, and used 1x2 along each long wall for added support. 16-18 feet long or therabouts.

Plain ol' plastic - well, it'll work if you secure it really, really, really well. No kidding - anything loose and it will flap it's way off, probably on the day you really need the protection.

The greenhouse plastic costs lots more, but the stuff I got from Northern Greenhouse Sales went on, even mediocre tightness, and stayed on. It's the kind of material you do once and replace maybe 5-6 years later. I did the cheap stuff 3-4 times (same season) before I figured it was time to use the real thing.

Venting is important. Cold days in the winter when temps were 35-40 and the sun shining - got me to 70+ inside during the daytime. When summer hits, temps go ballistic - you gotta have enough vents! I had a doorway at both ends I could leave open a bit for max cooling.

Good luck whichever way you go. You can help insure the structure with some clothesline secured over the hoop house (like the low row covers) with a bungee on one end, so the elastic ensures the rope stays snug to the plastic - helps keep the flapping to a minimum.. :)