Building a Hoop House

I've always dreamed about having a greenhouse.  As a child, I thought I'd live in a mansion with a nice greenhouse built in the back wall.  I always loved the idea of growing interesting plants all year long, and also starting seeds in late winter and early spring.  But, as an adult I realized that I'm a city person and apartment dweller, so no backyard or attached-to-the-house greenhouse.  Thus the ambition has been scaled back to running a greenhouse at a job.  Hoop Houses, also known as High Tunnels, are a nice economical way for farms to reap all the benefits of greenhouses, such as early spring seed starting, season extension, and for educational gardens, indoor gardening classes for rainy or cold days.   

Last fall we learned that another food-justice focused organization would fund a hoop house if we host a volunteer event.  I was thrilled, looking forward to the construction and then our winter gardening.  Then, I found out that the event could only be scheduled on January 20, to coincide with the Martin Luther King Day of Service.  My initial reaction was "Hell no!  Is people crazy?" but soon after I figured that there's no downside.  I think it was understood, although unstated... if there's a terrible blizzard on January 20, the equipment will still be ours and the event would be postponed.  It's not like we would be forced to put volunteers on high ladders with power tools, during a 20 degree, windy snow storm.  So, I agreed to run a big volunteer event in the middle of the winter, risk and all.  Anyway, we tend to have just as many cool January days in the 40s, as in the teens.  Brooklyn is not my native Chicago, where no outdoor event would be planned for January.  The catch was, that I was responsible for getting the ground ready for January 20, whether or not the weather would eventually allow for the event to go on.

Early January saw the so-called Polar Vortex.  Some people thought we couldn't do any work because the ground would be frozen solid.  But, as soon as the first post-vortex thaw, we got on it.  Time was a ticking.  I also learned was that if the top part of the ground is frozen, a few inches below is softer.  A little pick axing can solve the problem.

 

After choosing an ideal location and roughly measuring out the 36' x 20' foot print, a good crew of helpers and I began removing the rows of soil (every day that the weather allowed).  Then, we peeled back the landscaping fabric.  Soon, we had a clear space, apart from the four wooden raised-beds, which we would work around.  

I used a string level to see how much we needed to flatten the area, and it turned out that we were indeed on a big slant, in both width and depth.  So, the goal was to remove around 6-12" of base soil at the upper edges, and gradually fill it in at the lower edges.  

Unfortunately, that strategy proved more difficult to achieve.  Under each layer of soil and clay, there were tons of bricks, rocks, larger boulders and concrete.  The new strategy was to sink the upper posts a little deeper, and the lower posts a little shallower (and that remaining space will be filled in later).  The fourteen posts are 3' long, with 2' supposed to be driven into the ground.  There is enough room to make the above adjustments and still have a secure structure.  The posts would all be level, even if the base ground isn't.

Soon after we began breaking ground, our hoop house arrived!  This 800 lbs package was shipped from Iowa.




 

Luckily the instructions were clearly labeled so easy to locate!

One of my early tasks was to take inventory of all parts, big and small, to make sure we aren't short of any essential components on the big work day.

More ground leveling...

The big work day was scheduled on a Monday (Martin Luther King's birthday, observed), so we worked around the clock to get the ground ready during that weekend.  One of my carpenter friends came on Saturday and we drove in the initial post, measured out the four corners so they're perpendicular, then drove in the three remaining corner posts, and made sure that all four corners were at the same level.  Just getting these precise measurements took a few hours.  Then, we measured out the remaining ten post positions (seven posts on each side).  It was nice having a professional give me his opinion on just how precise we needed to be.  A few inches off in the X or Y direction was okay.

First corner post driven into the ground!

(See photo to lower right) The line level set to the first corner post will be used to set the level of the remaining three.  Here, the lines are perfectly level and perpendicular, and reach the center of the two adjacent posts, exactly 20 and 36' away.  Or more or less exactly.

On the Sunday before the big work day, we had a good group of volunteers come to drive in the final posts.  All the measuring was done, but still a full day of hard work. 

On Monday, my carpenter friend returned to run the crew.  The volunteer group of around fifteen people was very good, each taking their delegated tasks.  Here is the first hoop set in place.  Our good placements of the base posts, proved to be fine so far, as everything fit.  Before the second hoop was joined at the top to the first, we needed a lot of people (and ropes) to hold it in place. 

Once two hoops attached, the rest easy...

By the end of the work day, most of the main structure was completed.  All seven hoops, plus the straight bars (called "purlines") were up.  Now, it seemed that we just needed a few hours of warm weather to complete the project.

The day after our work day, there was a blizzard.  We totally lucked out with the three previous days being "okay" weather, cold and breezy but dry.

Over the next month or two, I tried to get out there with a few people to add the remaining components before the plastic. 

ribbon boards attached.

Ribbon boards and u-channels above, base boards below

First we added the ribbon boards and u-channels, which are shown in two photos.  These are ~ 4.5' above the ground, running the length of the hoop house.  The ribbon board is a 1"x3", which holds the aluminum u-channel.  The u-channel holds the plastic film, allowing a metal spring to wedge against it's walls, keeping the film in place. 

The next step was to attach the base boards.  These don't provide much structural support, but they form a horizontal support to prevent the base poles from sinking in the ground.  Kind of like a wide snowshoe.  They also help seal the side walls from wind.  We used some re-purposed scaffolding boards.
 

The plastic film, as it came in the original packages.

Finally, we were ready to contemplate the installation of the covers.  One of the rolls was 28'x28', to be cut into two 14'x28' sheets, for the end walls.  These would have to be trimmed to half circles, after installed. The other roll was 38'x40' for the main cover.

First piece of plastic being attached!

Finally in mid-April, the carpenter returned with his 10' ladder and he helped us install the end walls.  Another full day for five or six people on a Sunday.  We probably could have done this a bit earlier, but the winter was a bit too intimidating for me to push for anything more than small incremental steps.  Once we opened the plastic, it really had to git done...

Finally some visible progress!  Huge relief.  Now we have one end wall attached, sans door, but it's a start.  

One more thing accomplished on that Sunday, was that we installed another set of u-channels.  Once we installed the end walls, which were attached by metal clips and screws, we attached the u-channels right on top of the clips and plastic, on the upper-center edge of the two outer hoops.  The method is that the plastic cover will be attached to a continues line of u-channels, covering the two outer round hoops, and the 36' straight, horizontal ribbon boards (4.5' above the ground).  The remaining flaps of the cover will be secured by a roll-up mechanism, so can be opened or closed.  The aluminum u-channel material is soft enough to bend to the contour of the hoops.

End walls!

On Good Friday, we had another volunteer group coming as part of their Spring Break.  This group was mostly middle schoolers from out-of-state, plus a few Brooklyn high school kids, and some of our regular adult volunteers.  The timing was great because we needed many hands to hoist and pull the top over the metal structure.

We removed all sharp rocks and twigs, and laid out cardboard on the ground adjacent to one of the side walls, so the plastic won't get ripped.  Then, we rolled out the film along that area.

The plastic cover is gently set in place

We added three squares of Gorilla Tape as a reinforcement, and then cut a hole and tied ropes to the two end corners and one center edge of the plastic.  I was hoping that these would be strong enough to hold as we hoist the film over the top.













Three ropes were thrown over the top purlines.  Then, we had several people feed the plastic over the top, while three people "gently" pulled the ropes.  All three ropes did eventually tear their piece of Gorilla Tape and plastic, but we went on ladders to reattach.


















As the plastic got stuck, two of us were on the ladders to fix or push it along.  With only one 10' ladder and one 8', we had to constantly move the ladders horizontally to cover the 36' length. 












We also prodded the plastic up and over using the round, handle ends of shovels.  Once over the top purline, the rest was easy.  Before this point, each of the three ropes snapped, but cutting a new hole and re-attaching was easy from the ladders.  We had enough slack at the end of the cover, so a little damage on the final two inches wasn't a huge deal.  After more prodding, tugging, pushing and pulling, the cover was over...

Cover is finally over-the-top!

The next step, while volunteers were still available to hold down the corners, was to get on the upper peak of one edge hoop, and attach the initial spring.  The plastic gets wedged into the u-channel, and the spring pushes outwards, keeping it in place.  We followed the instructions, attaching springs in a continuous pattern, from one upper peak, outwards, and then the horizontal u-channels connected to the ribbon boards (4.5 feet above the base boards).  Any extra slack would be bunched together in a corner.

After all springs secured the perimeter of the cover, the next step was to connect the 36' poles (which were structurally the same as purlines, made of six 6' poles screwed together) to the edge of the covers.  These were clipped and screwed to the far edges of the two side flaps.  A handle was attached to an end of each side 36' pipe, which allows us to roll up the side flaps when needed.  Below is how our hoop house will appear during the summer months. 

Sidewalls in "up" position.  During the summer, we will tie up the opposite end, so there's no sagging.

So, we finally have a hoop house that's up-and-running.  There are a few more small things need to be added, such as the anti-billow cords on the sides, and then before November we're going to add a wooden frame to help support the end walls, plus we may add storm-doors for easy exit and entry.  For now, we will soon prepare the inside for growing.  We'll add more rows of soil, and also set up shelves and a table for some late seed starting.  We will also plant tomatoes a few weeks earlier than those that will be planted outside.

It would have been nice to have this hoop house up by early March, but we did our best.  Next Fall and Winter will be great.  For spring of 2014, we will still get some nice use, but I really look forward to the coming fall, winter and early spring.  There will be no more "off-season" on our small farm in Brooklyn.

 

Now we need to organize the inside, add more rows and start planting...

Turning an urban vacant lot into a farm

A Google Maps Street View of the space, "before".

Last summer I was hired by a food pantry to run their gardening programs, and also oversee the building of a small farm
on a nearby vacant lot.  A few months earlier, they already added fifteen wooden raised beds; I will describe the further expansion that I was involved with.


The large, 7,000 square foot lot was surrounded by raised beds, but filled with weeds.  Our goal was to turn the bulk of the area into growing space.  

Here are is the lot when I first saw it.

After making several phone inquiries, I chose to order soil from the Long Island Compost Company.  They delivered a "full truckload", which was 60 cubic yards, of a 50/50 topsoil compost mix.

Once we had the soil, our first task was to figure out what to do about weed control, and more importantly, soil toxins.

My employers already tested the base soil.  A many decades standing vacant lot has seen a lot of debris, so not only did the soil have very poor nutrients, it wasn't safe to grow food in the soil due to toxins. 

Our strategy was to block off the weeds with cardboard, and add landscaping fabric on top.  This doesn't create a perfect seal, but it is considered a standard procedure for growing on top of urban vacant lots.  Very few roots will penetrate into the base soil.  The vast majority of the plants' water and nutrients will come from the new soil, so the resulting food should be very safe...especially compared to conventionally grown crops that use toxic pesticides.  This isn't a perfect science, so all urban gardeners need to keep up-to-date on the latest findings and protocols.

Cardboard added for blocking weeds

Landscaping fabric added like a carpet

We blanketed the area with landscaping fabric, covering both the paths and the growing area.  The goal isn't to just seal off the planting area, but to prevent any of the base soil from blowing or spilling into the growing area.  The standing/meeting areas will be covered with mulch to do the same.
 

To the left, we are starting to add rows of soil.  We kept 18" paths between the 24" rows, so adults and school groups can easily walk through the rows.  Going forward, I would suggest creating wider growing rows.  30" rows with 18" paths is a good standard to follow.



We added wood chips and coffee bean sacks in between each row.  These paths made the farm look pretty cool, but after several rain storms, the lines got visually blurred.  My main goal wasn't to keep a nice clean space free of mud, but to create a clear, delineated set of paths, so that visitors will understand where they can and can't walk.  Often adults and kids alike will not quite get the concept of path vs. row, and we will find foot prints in the growing areas, which is a huge no-no.

Finally, the crops started to appear.  Planting started less than a week after our soil delivery, in early August.   Since planting is the easiest task, and the growing season was limited, we began planting every day after each new sets of rows were created.  Some of our crops were transplants, but most were direct sown.

Luckily the raised beds had some longer season crops such as tomatoes, peppers, eggplant and okra.  The only new things we added were root vegetables and leafy greens, plus a small amount of peas and bush beans.  The bulk of our new crops were kale, collards, chard, beets, turnips, rutabaga, pak choy, Chinese Cabbage, lettuce and arugula.  Nearly all were a huge success, so it's nice to know that one can still get a good harvest starting that late in the season.  Now, we look forward to the first full growing season!

Lacinato Kale

Lots of chard!

Arugula

Finally the season came to an end around the New Year