FoxDog Farm: High Tunnel Greenhouse, 2009
A New High Tunnel Greenhouse
We knew we were going to need another greenhouse. The glass house that is attached to the southern side of our residence is big (12 x 30 ft) but not big enough to grow enough tomatos and peppers for our CSA and family needs. So we researched various other kinds of greenhouse and finally decided on a high tunnel hoop house. These hoop houses are constructed from PVC and greenhouse plastic and are meant to be temporary. They can be moved if necessary and are useful in the field or as a greenhouse.
The internet provided various plans, and we eventually went with the design available here. We felt that this plan had several benefits. The primary benefit is that it seems to be very sturdy. FoxDog Farm is windy (we call it Siberia) almost every day, because we have water on 3 sides of us. The plastic is removeable for the winter, if we so desire and this will enable the house to survive windstorms and snowstorms. The construction is simple, with simple skills required. The tunnel is roomy, and will provide enough room for our tomatos and other plants. The construction costs wouldn't run too high, although they did go a bit higher than we expected. In a pinch we can move this hoop house.
Siting
We decided to put the high tunnel near our glass greenhouse, so that it would be easy to transfer plants between the two. This also facilitates watering and any electrical needs we might have, although we forsee not needing electricity in the high tunnel and haven't planned for it. Therefore, the high tunnel is sandwiched between the goat area and the lawn, set amongst a few trees. The trees provide some shade, but it's only really a factor in the winter, when we don't think we'll be using the tunnel. In fact, the tunnel will probably have the plastic removed for the high winter.
Randy did a lot of work on the site we'd chosen as it had been something of a rough dumping ground previously. There was a lot of old farm junk there and dumps of excess gravel that we'd used in our herb garden. The willow tree/bush had to be cut back. The goats loved the trimmings!
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The area for the new high tunnel, prepped for construction.
The area which will be in front of the hoop house. The trees were planted 15 years ago, and are quite tall now.
Day 1: Setting up the Hoops/Bows
The plans called for an ingenious use of different diameters of pvc pipe to created the framework of the high tunnel. The hoops or bows are 1.5 inch pvc. They are set into 2 inch pvc anchors which are pounded into the ground. These are held stable by a framework of 2x6 lumber(the baseboards) and secured by carriage bolts. The plans linked to above are really good about explaining what is needed, although there is an error concerning this section of construction in the parts list. Ten 10ft long 2x6s are required, not 6 as listed in the parts list. Also, the carriage bolts for the purlins should be 5 inches long, not 4.5 inches. And you probably don't, or can't drive, 2.5ft of pvc anchor into the ground unless you have really silty ground. We have mucky clay with a hard clay layer about 1 to 2 ft down, and we couldn't drive them through the clay layer.
Our chosen site slopes down to the east. This is good because it makes drainage really easy. However, it also makes the construction a little unusual. We had to step down the baseboards and, eventually, the bows/hoops.
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Here we are laying out the baseboards after running plumb lines.
The baseboards were stepped down to deal with the slope of the site.
Jodie and Dave are cutting the bow anchors from the 2" pvc. Randy is 'helping'.
Randy pounding in the bow anchors. Dave is bravely holding the anchor steady.
The bows anchors are in, but they need to be cut flush with the baseboards.
Here the bow anchors are cut flush with the baseboards. We should have paid more attention to getting them super straight when we pounded them into the ground.
The bows are 30 feet long, and need to be assembled from two lengths of pvc (which generally comes in 20 ft lengths). Here they are laid out and primed for gluing.
The bows went up fairly easily, considering how long they are. Once they are bent, they will shatter if you try and straighten them too much. So care must be taken.
Jodie and Dave putting up a bow.
The bows/hoops are secured with carriage bolts through the baseboard and bow anchors.
Our youngest goat, Genevieve, checks over the trash pile for anything fun to play with. The goats supervise all the farm work, and Genevieve is learning her managerial position.
We quickly learned that the pvc will shatter if you drill too much through it. It sets in the bow shape very quickly and gets brittle under tension. We shattered and had to replace one bow after we tried to drill it the next day.
Day 2: The purlins and the hipboards
To stabilize the structure, and to create places to conveniently hang tomato strings, we wanted to put several purlins down the length of the hoop house. The central, and highest, purlin is secured by drilling down through the two pvc pipes (the purlins are pvc). The pipes are then held by carriage bolts. As mentioned above you really need 5 inch bolts for this, not 4.5 inch. Or, at least, we really needed them.
We got nervous about drilling through the bows after one shattered and decided to attach the two outside, and non-structural purlins by zip ties. We'll see how this works out, we might replace them with wire or some other kind of assembly.
The plastic which forms the cover of the hoop house is secured on hip boards which are about 3 ft above the baseboards. The plastic can be secured via lathe strips which are screwed down over it, or via wiggle wire strips. We used wiggle wire, so that the plastic would be easier to remove. The plastic is not screwed to the baseboard in order to provide an easy way to vent the greenhouse. The lower sides can simply be rolled or lifted and air can then enter the greenhouse when needed.
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The purlin was tricky to do with so few helpers. Here Dave is holding up the purlin while Randy wields the drill.
The drilling needed to attach the central purlin shattered one of the bows/hoops. Luckily we had 2 side purlins with which to replace it. The broken bow was glued back together and used as a side purlin.
The central purlin is in place. After this was done, we decided not to do any more drilling and to attach the side purlins some other way. Our handy dandy goat-fence makers, zip ties, came to the rescue.
The CEO of the farm, Reyna the FoxDog, got a bit tired out on the job. That happens when you are 14 1/2 years old, or umpty-teen human years old.
The hip board being installed. We decided to not step this down, as we had the baseboards, because then it would be awkward to roll up and down. Instead we lowered it a bit at one end (2 ft high) and raised it at the other (4 ft) to make it level.
The farm chairwoman of the board, Miss Mack, came out with her daughter, Genevieve, to inspect our work. It must have been take your daughter to work day!
The hoop house with purlins and hipboards. The hipboards have the wriggle wire channels attached. We still need to do the end walls and then put the plastic on. That'll be on days 3 and 4!
Days 3 and 4
Technically, it should be days 3 - 5, but we only did partial days work on all of them. Randy and Rikke built the endwalls on the third day. They were fairly easy to do, although we could have used a mitre saw at one point. We also added the lateral bracing from the end walls to the baseboards. This made things really sturdy.
The plastic greenhouse film comes with instructions as to how to put it on the house. Ours was delivered in a 'W fold', so that it was folded up from the edges along a center line. Instead of unfolding and pulling the whole thing over the bows of the house, the instructions said to feed it along the topline (the top purlin in this case) and let it unfold by itself. This worked like a charm, although it was rather difficult to feed it with only 4 people. Jodie and Rikke kept the film rolled up on a spare piece of PVC pipe, so that it wouldn't unfold. Dave stood in the back of the pickup and fed the film up to the purlin. Randy, the strongest of all of us, tugged it down the length of the purlin. Much cussing and panting did ensue, but it went on great.
After the plastic was on, we had to put the plastic on the endwalls. Randy and Rikke did this on the fifth day. It was pretty easy. We used a staple hammer and the wiggle wire channel, making sure that the top piece of plastic was not stapled, but only held by wiggle wire. This is so it's 'easily' removeable. Then we cut a door in the plastic and put up an old screen door we had laying around. We used the handy-man's friend, duct tape, to put the plastic on the door (we'll come up with something better later) and we were all done.
The greenhouse is very effective. It's steamy hot in there during the day, and it cools off fairly quickly at night. I would not grow anything in it in the winter, without using reemay as well. During July and August I expect that we'll have to vent it by lifting up the plastic along the side bottoms. Right now, that's not needed.
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Here is our framing of the end walls, before we put the bracers on.
The plastic arrived on a tube. We put a pvc pipe through it and rolled it out handily. The 'W fold' is pretty visible in this picture.
Dave is under the plastic, somewhere. Jodie is at her end of the pvc pipe roll. Rikke is taking the picture, and will be lifting and unrolling the other end of the pipe when it's time.
This shows Randy pulling the plastic down the purlin, and Dave is still under the plastic on the end of the truck, somewhere.
Looking through one end towards the other, which has plastic on it. Eventually we'll cut a door in this end, when we find another old screen door to use.
The near end wall with plastic on it, and the door cut out. On the ground inside the house is the 6 mil black plastic we will use as green house floor.
It's been a long week of hard work, with 14 hour days at times. Randy's camped out in the warmth of the hoop house. Note that this is before the addition of the plants and water, when it will become unbearably humid in there.
Here's the screen door framed in and on. It won't withstand a windstorm and we'll have to replace it with something sturdier in the winter (if we decide to use the house in the winter).
We gave the hoop house a name, in honor of our friends who helped us put it up.
Casa Emmons was really needed. The glass greenhouse was full to the brim with tomatoes and peppers. Here it is before we started moving the tomatoes out. It's impossible to water in the far corner at this point.
The other side of the glass greenhouse, stuffed just as full. Hard to believe that these plants were tiny seedlings just 45 days ago. Now they are flowering and putting on fruit!
The hoop house is so big that we are going to have a lot of room for growing. Of course, standing on a ladder to pick tomatoes is going to be interesting. Here are the first of the plants after moving and being attached to string for support.
