The planning is over and the construction of my hoop greenhouse can begin. I decided to begin the construction by building the end walls first – even though it would be more fun to throw up the main structure in just an hour or so and make a big showing of progress.
I temporarily attached a joint of pipe to a piece of 1×4 to establish the outline. You might be tempted to make your greenhouse wider and lower at this point to get more floor space out of it – but be careful. If you have snow in your area, it will slide off of a high peak a lot better than it will if your greenhouse has more of a flattened shape -the same goes for heavy rains. If your greenhouse is to flattened, it will cave in the first time is snows or pours down!
Pre-drill the pipe and use one screw so that the pipe can swivel to whatever angle it naturally aligns to.
For now just let the wood “run wild”
I used pressure treated lumber for much of the polytunnel end frames (even though I usually try to avoid treated wood in the garden). In this case, I think it’s called for, or else the greenhouse probably wouldn’t last more than 2-3 years without rebuilding the frame.
Build the rest of the frame to accommodate the door size that you want to use. My door will be 5 feet wide, but in most cases 3′ wide would be adequate. If you want a longer lasting greenhouse, you should use “two by” lumber instead of “one by” that is shown here. Leave the piece that runs across the bottom of the door in place for now. Once everything is set in place, it will be easy to cut out with a hand saw.
I used a bit of weather resistant glue, at all of the joints, to help make it all more rigid. Notice the wood recycled from concrete form lumber.
Mark the final outline once the wooden parts are assembled. Watch out for that screw when you saw to the line!
Now just trim to the line – I used a reciprocating/sabre saw, but you could also use a hand saw or circular saw if it’s all you have. Just make a straight cut in about the right place.
Now re-attach the pipe to the outside of the frame (I used screws and wire ties because I’m a belt *and* suspenders kind of person). The end wall frames ended up being reasonably light and very rigid. BTW, you might notice that the second one is different (simpler) from the first one because this is a learn-as-I go process. Both of them work fine though.
Notice that the plastic that will be the roof and sides of your greenhouse are going to fold over the ends and staple to the wooden parts. If you don’t have enough wooden structure in the ends, you won’t be able to fasten the plastic and you will have trouble with it coming lose when the wind blows – and during heavy rain or snow you will be more likely to have problems with the very top sagging and holding water (or snow).
If the top sags, it holds water, that makes it heavy and it sags more, then it holds more water… eventually it collapses. You don’t want that, right?
Now for the plastic
The plastic sheeting that I’m using is plain old non-UV stabilized 6 mil “clear” plastic sheeting from the lumber yard. There is exactly one reason why I am using this particular variety instead of special polytunnel. Greenhouse plastic – it’s what I have. I cut a 22′ piece off of a 100′ x 20′ roll (which was about $90 for the roll). So in essence I used about $22 worth of plastic sheeting after you apply the 10% TN sales tax.
Also, It’s hard to buy large pieces of heavy duty plastic like this without buying a whole roll, so unless you know a contractor or Mom and Pop hardware store that will cut you a piece, you might really be better off ordering some of the good stuff. On the other hand, a big roll of plastic sheet is one of those things that comes in awfully handy sometimes.
I just rolled the plastic out on the frame…
and cut it off nice and clean with a sharp utility knife. A scrap of wood to cut over and a sharp knife make this much easier.
after stapling the plastic to the front, flip the frame over and fold over the plastic and staple it to the back. Just fold the excess together as you go. Fold in the direction that will be down so that condensation won’t collect under the folds.
Then trim off the excess. Be careful not to make a miss-cut!
Cut the plastic out of the door opening – leave enough to fold double before stapling it to the frame.
Notice the cuts back to the corners of at the top.
Mark out the locations of the door sides on the ground, and drive fence posts or long pieces of rebar at the sides of the door frame.
If you have too much wind, I would recommend using steel fence posts or rebar that is at least 5/8″ diameter in these spots. My fence posts don’t match because they’re leftovers from previous projects – remember, I’m on a tight budget!
Check the fence posts for plumb and bend them a little if they need straightening.
Tie the hoop house end frames to the fence posts with wire ties, wire or rope. The humongous wire ties made this really quick easy and strong, but If I didn’t already have them I would just use “baling” wire, and it would work as well.
Once the end frames are in place pull a string to line up the stakes for the ribs.
Drive rebar pins every 3 feet to secure the intermediate ribs.
At this point, it takes about 2 minutes to install the pvc pipes for the intermediate ribs – and the polytunnel takes shape. For a stronger structure use more ribs and put them closer together – or even use larger pipe.
I haven’t tried it, but I bet you could use up to 1 1/2″ pipe – although you might have to bend it into shape on a warm day.
As you can see it’s getting dark, and I’ll have to finish this later. Total time invested so far is about 2 and 1/2 hours. I believe that taking the greenhouse down next summer, and re-assembling it in the fall will probably only take an hour or so.
Since the site location where I’m building my greenhouse isn’t all that level I had to raise up one side of the end frames with some 2x6s that I ripped to fit – later I cut the tail off where it sticks out toward the fence. Also, notice that this means that the PVC pipes that are the intermediate ribs are too low where they hit the ground.
So, I extended them with some scraps of PVC conduit that I had – I never throw anything away. BTW, the gray PVC conduit is sunlight resistant unlike the white. You should probably use the gray conduit instead of the white pipe that I used.
If you live where it snows or even rains heavily, you need to add a 2″ pvc pipe to the very top of the frame like this:
This 2″ PVC ridge on TOP of the frame keeps the plastic from sagging in snow or hard rain and prevents the structure from collapsing.
I ran a screw up through the ribs into the 2″ ridge pipe, but I also tied a peice of 1/4″ rope around each intersection as well – I don’t trust screws alone in a spot like this.
When I originally built the greenhouse, I did not use the ridge pole, and it collapsed under a snow load! Since adding this feature, the structure has been through several snowfalls with no problem at all. However, when I know snow is coming, I have two 2×4 props that I put under the ridge just in case.
I strung it all together with 1x2s that I ripped out of some slightly used 2×4 studs. Using full 1x4s (which I later did) or even 2x4s for the top set of these would make the structure stronger.
I used a few wire ties to get everything located, and then drove a 1 1/4″ drywall screw at each joint to secure it. As you can see by the lay out marks, I first measured and marked all of the locations so that it would go together reasonably straight.
If you look really close in this picture, you will see the wires that serve as X bracing on the sides.
I used a doubled wire that I attached at the top and bottom of the ends using a washer and a screw.
I then used some scraps of wood to twist the double wires together and tighten them up like a rubber band airplane. You just want them to be snug, so don’t go nuts tightening them up. These wires really go a long way to make the whole structure more rigid and sturdy.
Now for the plastic covering – measure and cut your piece of plastic – you need a little extra in all directions – the piece that I used is 20′ x 22′.
My greenhouse is 15′ feet long so I cut a 2×2 x 15′ – Here I’m positioning it in the center of one of the 20′ edges of the plastic – leaving 2 1/2 of plastic past the ends of the 2×2. Staple it together, just to hold it in position.
Now roll the 2×2 under one complete turn so that the edge you stapled is facing up under the top layer of plastic sheet.
Now screw a 1×2 on to secure the plastic. By wrapping the plastic around the 2×2, and then sandwiching 2 layers between the 2 pieces of wood you make a very secure connection, and also add some weight to the bottom edges to help keep them from billowing up in the wind. Do the same thing to the opposite edge, and then roll it all up and get someone to help you carry it to the hoop house and unroll it across the top…
… Now you almost have your greenhouse.
Roll under the edges on the ends and staple them securely.
(Note: now that I have taken this down for the summer, I think that when I put it back up next fall instead of “stapling it securely” I’m going to just staple it a little bit to get it positioned, and then screw battens made of 1×2 or strips of plywood to hold it in place – it should be stronger and quicker)
Other than the doors the structure of your polytunnel greenhouse is finished. Total spent time at this point is about 6 hours. Everything is a bigger job than it seems like it’s going to be. Rake soil or mulch up to the gaps at the bottom to keep out drafts and (larger) critters. Cats in particular are likely to be attracted to such a nice sheltered spot with a bed full of soft loose dirt to dig in so pay attention to the details. Rocks, bricks or concrete stepping stones or blocks placed on top of the soil/mulch around the outside edges are probably a good idea.
This greenhouse uses clips made of sections of black poly pipe to attach the skin.
Before I even started on the hoop house, I tilled copious amounts of compost into the beds where the greenhouse was going to end up. So, even though I probably won’t get a chance to put up the doors until next weekend, I’m all ready to plant some lettuce and spinach for (hopefully) some fresh mid-winter greens. One of my goals in building this polytunnel is to have something fresh coming out of the greenhouse all year around. That might be a little optimistic, but I’m going to give it a try!
It’s time we all became a little bit more self-reliant
Since the mainstream idea of food production is becoming increasingly more out of touch with nature, it becomes clear that we need to begin thinking about growing our own food the nearest we can.
We can always go down the organic isles at the supermarkets, but sometimes the costs can be so high that we quickly go broke. In the end, we still don’t quite know where that food originates from.
And there’s more to it! Many a time even organic food we buy at supermarkets has traveled many miles before it got onto the shelves. This means that there are fewer nutrients in it than shown in the labels.
Complete list of materials for “Greenhouse”
Each Qty Total
$4. 23 6 $25.38 20′ x 3/4″ PVC schedule 40 plumbing pipe
$6.70 6 $40.20 1x6x8′ pt – ripped into 1x3s
$4.99 4 $19.96 8′ steel “T” fence post
$2.18 3 $6.54 2×4 stud – rip into 1x2s
$3.97 2 $7.94 1x4x12′ pt
$5.73 1 $5.73 2x4x16′ rip into 2x2s
$7.91 1 $7.91 20’x1/2″ rebar – cut into 18′ lengths
$4.88 .75 $3.66 8″ nylon wire ties – 100
$5.47 .5 $2.74 1 1/4″ x 1lb drywall screws
$6.97 .3 $2.09 16 guage galvanized utility wire – 200′ – for X braces
$2.97 .25 $0.74 3/8″ t-50 staples – 1000
$79.00 .22 $17.38 20′ x 100′ x 6 mil clear plastic
Scraps of plywood for reinforcements – scrounged
Finally, the food traveling around the world is not a nature-friendly way to bring food to our dinner tables.