Johnny's Quick Hoops™ Gothic High Tunnel & DIY Seedling Heat Mat
After a season of spending countless hours in 2016 driving to and from our tiny greenhouse located on family-owned property in Dartmouth, MA, we decided it was time to invest in a new heated space. With limited funds available after buying all of the necessary seeds, supplies, & amendments for our 2017 season, we were open to exploring any cost effective method to starting our transplants. I was introduced to the Quick Hoops™ Gothic High Tunnel system designed by Eliot Coleman with help from Johnny's Selected Seeds at the Young Farmer's Conference held at Stone Barns in NY. I was immediately drawn to the simple design that used supplies available at any local hardware store, eliminating the high cost of shipping usually associated with such projects. As we researched the possibility of using this system to create a new greenhouse, we found it to be a great fit for a temporary greenhouse that could be used in our fields for season extension after all of our transplanting is complete. We decided to build two modules for a greenhouse that is 14'x32'
It is helpful to gather all tools and supplies before you start, here's a list of what tools we used:
-Electric cordless drills (having 2 was very helpful)
-5/16'' drill bit
-1/8'' drill bit
-Ratchet set ( 1/2'' )
-Clamps (at least 6 are helpful)
-Phillips head driver bit
-5/16'' hex head driver bit
First, we placed our orders with many different purveyors in order to save money on supplies. We used the calculator to figure out exactly what supplies we needed and brought them out to the farm. There was still a good 12 inches of snow on the ground when we started but luckily the weather warmed up for most of the time we were building.
We spent the first day measuring, cutting, and pre-drilling all the pieces to make assembly quicker. We would suggest that you read the whole instruction set before beginning because some of the instructions are a little out of order and you could save time by crimping and measuring/cutting everything at the beginning. We started by setting up the bending jigs from Johnny's and bent all of our side hoops and peak sections. For the side hoops, we found it best to slide the 1 3/8'' top rail through the side hoop bender a foot or so at a time and bend it bit by bit for a smoother, straighter bend. We lag bolted it to a stack of very large, heavy pallets and had one person bending and one person receiving the pipe to keep it from corkscrewing. Make sure whatever you bolt the bender to is heavy enough to not move.
Timelapse of bending the peak sections and side bows:
By the day's end, we had bent the side hoops and peaks, measured and cut the rail for the bottom rails and ridge pole, and crimped the ends of the 3/4'' EMT for the cross bars.
I apparently did not get any photos of us setting up the jig to assemble the bows, but it is pretty self explanatory if you follow the instruction manual. We found it helpful to make sure the measurement from the top of the peak to the brace bands was equal on both sides to make sure the collar tie was straight. Pre-drilling through the brace bands was very necessary so keep that in mind.
After the bows were assembled, we lined up the bottom rails and measured the distance between corners to square the base. We then got them standing by inserting them into the T clamps along the bottom rails. It is helpful here to read a few steps ahead and to slide on the brace bands in preparation for the corner braces, knee rails, and end wall angle braces. You can save some work by ordering a few extra T clamps for the knee rails instead of brace bands so you can avoid crimping and drilling the ends.
For the ridge pole, we followed the directions and lined it up with the bows to figure out where to pre-drill. We would suggest drilling all the way through with the 5/16'' bit and then reaming out the top hole with a slightly larger drill bit to accommodate for the square shape under the head of the bolt. We were worried that if the head of the bolt stuck up above the peak that it could catch on the plastic when we were covering it.
After the ridge pole was up, we put on the corner angle braces and started on the second module.
The two modules ready for wiggle wire channel:
We found it easier to pre drill through the wiggle wire channel even though we were using tek screws. Using strong clamps was important as well as using one clamp from each side to prevent it from springing back when you were bending it around the bows.
After the wiggle wire channels were installed, we assembled the poles for the scissor doors.
The next step was the plastic! Luckily it was a calm day with a few small gusts but very manageable. Throughout the process we had between 3 and 6 people helping at once. It's helpful to have one person at each corner on the ground and one person on both ends on ladders to pull it taught.
The instructions recommended setting the houses 1 foot apart and leaving extra plastic on each module to overlap and lock it into the wiggle wire on the tunnel. We found this extremely challenging and frustrating because it meant you had to stand on a ladder and blindly reach your hand up and over to attach the plastic. You can not really get over the tunnel enough to attach it, I don't know how they expected anyone to do that! We aborted that plan after about 45 minutes of trying and decided to cut a 1.5' strip of extra plastic and used that to bridge the gap, starting at the bottom rail of one side and working up and over the peak. We started by putting one piece of wiggle wire in the channel on one tunnel, then alternating sides along the way. The calculator did not recommend for us to buy enough wiggle wire as we needed so we pulled up the wire on both modules on the connecting end bows and put the two pieces of plastic under one wiggle wire. It probably doesn't look as neat as the other method but it was simply impossible for us to do and aesthetics weren't our major concern.
Once the plastic was on, we got the roll up sides together. The tek screws proved to be difficult again here and the drill slipped a few times and poked the plastic roll up side. We avoided this by putting a piece of cardboard over the plastic to guard it from getting poked as we were putting in the screws.
We used wood pallets to temporarily anchor the tunnel before we could get the ground anchors in. One of the final projects was the scissor doors. We opted to put in a 5/16'' x 5'' eye bolt through both doors and the knee rail as the instructions suggest to close the doors securely during windy days or the off season. We secured this eye bolt with a wing nut for easy removal. We used some duct tape to cover the sharp ends of the end wall angle braces because they caught on our clothes as we stepped into the tunnel.
We drove in the ground anchors by hand using the body of the hook & hook turnbuckles through the eye of the anchor until we had enough room to swap it for a piece of rebar. We attached the eye bolts horizontally to avoid the end of the bolt poking he roll up sides / scissor doors.
We put a few finishing touches on like screwing eye bolts through the scissor door and the end wall angle braces so we could keep the doors open to vent. We used a small carabiner clip to attach the eyebolts together and keep the door open. We found this to be the easiest solution for venting and using the scissor doors as an entrance.
This is how it looks from the inside when the door is open for venting:
If you face the eye bolts in the same direction on both scissor doors you can use the carabiner clips to keep the doors temporarily closed when you're inside or going in and out. It was very windy this week so this came in handy as we were getting set up.
Here is a view of our more permanent door closure for over windy nights or during the winter to keep it on lockdown. It's a long eyebolt with a wing nut to keep it closed. This eyebolt is longer than we would have preferred but it does the job.
We got right into setting everything up so we could start seeding our alliums! Our goal was to use as many low cost options inside as we could to make this project affordable. We have opted for milk crates as the legs for our pallet table tops. All milk crates were donated to us from friends at restaurants and the pallets were from a furniture warehouse we got for free from Craigslist.
DIY SEEDLING HEAT MAT
We also made a DIY seedling heat mat that was inspired by the video we watched here. The materials were as follows: 4' x 1.13' foam insulation boards from Lowes ($8.48 for a 6 pack) 48' soil warming cable from Amazon ($26.00) 1/2'' insulated metal cable staples from Lowes ($3.98)
48'' wide aluminum screening in "bright" color (it should be bright aluminum colored) from Lowes ($9.98)
Excess greenhouse plastic or painter's plastic
Wood pallet (40X48)
Most people can find duct tape, plastic, and a pallet, so without the expense of those items the total cost would be $48.44 This is about 1/4 the cost of most other heat mats. To get the same square inches of coverage you would need to buy two of these heat mats and they cost $79.99 each!
This design may not be perfect for everyone but so far it has been working for us. The cool thing about it is also that you can make any shape/size given that the soil heating cables come in different lengths. If your potting benches are not the same size as pallets as ours are, it can easily be adapted to any other shape.
The foam boards we bought from Lowes perfectly fit a pallet when laid out three across. The package came with 6 boards so we just doubled them up to give it more strength in case we needed to move it. We used duct tape to attach the boards together and lined the edges with duct tape to make it sturdier.
Next we laid out the heating cable. It has to be laid out in a way that the cables never touch each other and we used insulated cable staples to hold it down. It is a continuous loop of cable that has a thermometer at one end and the power cord at the other end.
It took a few tries to figure out how to lay out the maze but the styrofoam and insulated staples are easily moved.
Next we cut a piece of aluminum screen a little larger than the top of the heat mat so we could fold the edges over to avoid getting poked by the sharp metal. We used duct tape over the edges of the screen to keep it from fraying and used insulated staples to tack it down in the 4 corners. After that we laid a piece of greenhouse plastic over the top and also tacked it down with the staples from the sides.
That's it! It only took us a trip to Lowes and about 20 minutes to make it.
You can see it here covered in 10x20 trays. You can fit 8 trays on it at one time with a tiny bit of the trays hanging off the edge. For us, this works because we use soil blocks that don't fill the entire tray so we can hang the empty row off the edge of the mat.
Thanks for reading! If you have any questions feel free to email us at firstname.lastname@example.org -Jordan