Introduction: The Hydroponic, Automated, Networking, Climate Controlled Greenhouse Project: Construction

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This Instructable will cover the construction of my Hydroponic, Automated, Networking, Climate Controlled Greenhouse Project. The construction phase of the project covers the concrete footings, the framing and the glazing of the greenhouse.

Other Instructables that cover elements of the "Hydroponic, Automated, Networking, Climate Controlled Greenhouse Project" are listed below with many more to come:

Part 1: The Construction of the Greenhouse
Part 2: The 72 Plant Vertical Garden

The greenhouse when completed should be equipped with a large, centralized hydroponics system capable of supporting up to 40 large plants (tomatoes, bell peppers, banana peppers, etc.) and up to 72 small plants (lettuce, spinach, strawberries, etc.) for a total of up to 112 plants. The greenhouse will be equiped with an arduino based climate control system capeable of monitoring the indoor environment through a variety of sensors (temperature, light intensity, humidity, CO2 concentration, etc.) and automaticly adjusting each variable by controlling different devices (exhaust fans, louvre doors, heaters, grow lights, solenoid valves, pumps, etc.). The readings from all the sensors as well as the on/off status of all of the devices should be sent out over the internet and be viewed remotely and in real time from any computer or mobile phone.

As of this moment the greenhouse's skeleton is all that is completed. I didn't get as much done over the summer as I had hoped because of the nasty weather. However, over the winter I am working on constructing most of the hardware to go inside the greenhouse including the climate control system. I hope to be up and running by the time it's warm enough to start growing.

Each major section of this project should be it's own instructable and when it's all finished I'll compile it into a guide. For now I'll show you how I went from patch of land to a greenhouse skeleton.

Step 1: Considerations to Make Before Starting

I would venture to say that the single most important thing to consider when choosing a site for a greenhouse is sun exposure. A greenhouse should get as much sunlight as possible and in order to accomplish that it should be exposed to the open southern sky. Large objects on your property such as your house, a garage, a tool shed, fences, trees and embankments tend to cast long shadows on their north side and you don't want your greenhouse in any of them. This isn't much of a problem in the summer months or at low lattitudes but at high lattitudes in the fall, winter and spring this effect is quite profound. For instance, I live at 48 degrees North latitude and on a sunny winter's day my house casts a shadow almost all the way across the street.

In my particular case I got lucky because my backyard is totally southern exposed. The rear wall of my house faces almost perfectly south. It's only off by about 7 degrees to the east. I knew that I wanted to have both a garage and a greenhouse and my backyard is too narrow to put them both side by side. Even if I could put them side by side, the greenhouse would be in the shade of the garage either in the morning or in the evening, depending on which side it's on. So my solution was to put the greenhouse behind the garage.

The first picture is taken from an upstairs window looking south out over the backyard. The large orange rectangle closest to the camera is the site for the garage while the smaller rectangle out farther to the south is the greenhouse. The second picture is an "after" shot from the same location to clarify the meaning of the first picture.

You should also think about your local laws and building codes. In my municipality a building permit was required for my greenhouse and I had to follow a number of rules such as a 1.5 meter variance, a maximim size of 33% of my backyard and to keep it behind my building line (it has to be behind my house, not in front) to name a few. If you want a hydroponics system you may have to dump waste nutrient solution into the ground from time to time. Your town may forbid this, especially if there are drinking water wells nearby. You may also be required to let all of your neighbors know in advance and you might not be able to build if any of them have any objections. You should find out all of this in advance before you build because if you violate any municipal laws you'll probably be forced to tear it down and pay a fine.

Step 2: Preparing the Site

Once I decided where I was going to build the greenhouse the very first thing I did was use some orange marker paint to draw an outline of the greenhouse in the exact location I wanted it.

The next thing was to dig a trench about a foot wide and a foot deep centered on the orange lines. The trench is located directly under the concrete footing of the greenhouse. The trench would later be filled back in with crushed stone for the purpose of collecting excess rainwater and snow meltwater and directing it into the french drain that will run along my west property line about 5 feet away. Excess water underneath the greenhouse footing is bad because if it freezes it may lift the concrete and crack it up.

Before the trench was completely filled with stone I prepared a piece of PVC sewer pipe and laid it in the channel that connects the greenhouse trench to the french drain. The sewer pipe serves as a drain for waste water and nutrient solution from inside the greenhouse.  The sewer pipe will connect with the french drain and direct waste water into the storm drain (ditch) in front of the house.

Once the sewer pipe was in place, the entire site was filled with crushed stone, leveled and compacted with a vibratory plate compactor (or a "Jitterbug" as I like to call them). The Jitterbug is necessary to ensure the concrete has a nice firm surface to be poured on. The difference is actually quite remarkable. Before the Jitterbug the loose stone felt almost like walking on sand but after the jitterbig it was like walking on asphalt.

Now we're ready for the forms!

Step 3: The Concrete Form

I decided to build the greenhouse with a concrete footing mostly to discourage our infamous Newfoundland winds from picking it up from my yard and delivering it swiftly to the next town. In September of 2010 when Hurricane Igor hit, that's almost precisely what happened to my neighbor's patio of about 10 by 15 feet. So yeah... concrete footing it is.

The footing itself is 5 1/2 inches tall by 5 1/2 inches deep going all the way around the perimeter of the greenhouse. The outside dimensons are 10 feet 2 inches by 14 feet 2 inches and the inside dimensions are 9 feet 3 inches by 13 feet 9 inches. The framing is 2 by 4 lumber  so when the bottom wall plates are placed on the concrete the is an inch of concrete exposed all the way around both inside and outside.

The form itself is constructed out of 2 by 6 lumber with some 1 by 3 strapping for braces. This should be pretty stright forward to anyone with decent DIY skills. I built the form in the driveway and then moved the whole thing into position later.

Next came the anchor bolts and rebar. I drilled holes in each piece of strapping and inserted the anchor bolt, secured temporarily by the washer and nut. Then came the rebar. I bought the rebar in 8 foot lengths so it worked out that I only had to make one cut to get it all to fit right. That cut I made rather tediously with an angle grinder. I took advantage of the hook shape of the anchor bolt to hold the rebar up off of the ground a little, so that it is suspended inside the concrete rather than underneath it. Everything was tied up nice and tight with tie wire before calling that a day.

Before pouring the concrete I made sure everything was nice and square by checking the measurements of the corners. The distance between each pair of opposite corners should be the same or it's not square...even though it may look like it.

FInally, the last picture shows the PVC sewer pipe for the greenhouse drain. It goes from the inside of the greenhouse, underneath the footing and ends right where the french drain will be running perpendicular to it.

Step 4: Pouring the Concrete

This step was not fun at all. I mixed all of the concrete by hand in a wheelbarrow with a spade shovel... all 300 or so liters of it. It was a lot more work than I thought and if I could do it again I would have got one of those minature mixers that you can tow with your car.

I bought bags of portland cement and followed the recipe on the bag to make concrete. The recipe is 1 part portland cement to 2 parts sand to 3 parts crushed stone. I had a truckload of crushed stone on hand for my landscaping and I went to the local quarry to buy about 30 gallons of sand for 5 bucks. By buying the portland cement and following the recipe instead of buying bags of premixed concrete mix I saved a ton of money. It's not rocket surgery.

Once I had the form filled and the concrete screeted relatively smooth what I should have done was tapped the form all the way around with a hammer to work all the air bubbles to the surface. Instead I completely forgot to do this because I was so frustrated with mixing all of that concrete by hand as quickly as possible I was just glad to be done. The result was some rather rough looking concrete refered to as "Honeycombing" in the masonry trade. To fix this I made some sand/topping mix from 1 part portland cement to 3 parts sand and trowled it onto the footing to make it smooth, much like frosting a cake. I wet the concrete with a spray bottle as I went along to help stick the topping mix to the concrete. I had to fix the "Honeycombing" so that water couldn't pool in all the crevaces in the concrete and freeze, cracking ti all up.

Step 5: Framing and Erecting the Walls

The walls are very simple structures consisting of a pressure treated bottom plate, a spruce top plate and 81 inch tall studs spaced every 24 inches. The total hieght of the framed walls is 7 feet. The two 14 foot long walls worked out great because the length of the wall is an even multiple of the stud spacing. The two ten foot walls are actually 9 feet and 5 inches long to allow for the thickness of the two longer walls butting into them. The total length then becomes ten feet. The stud spacing on these shorter walls must then be adjusted accordingly. The center of the first stud must be 24 inches from the outside of the longer wall, not the edge of the shorter wall. So when you're marking out the stud locations of the shorter wall the first stud must be centered 20 1/2 inches from the edge.

One short wall is a little different because it has a doorway in the center. Not too hard, just a 24 inch opening with a jack stud and a king stud on each side and a header on top.

Before the walls could be erected I had to drill holes in the bottom plate for the anchor bolts to pass through. This was easy enough, just measure, mark and drill. If you have a friend this would be a good time for some help. I was alone at the time so I had to carry the walls over from the driveway and then lift them up over the anchor bolts and then lower them into place by myself. Have some lumber ready to use as temporary braces because the walls will not stand up on their own.

Once all four walls are in place all nailed together with an overlapping double top plate it's just about time to start roof framing.

Step 6: Framing the Roof and Installing the Purlins

A complete explanation of exactly how this was done will require a pretty deep excursion into framing methods and tool usage and measuring and marking devices and the like. However, it wasn't hard and it turned out well. It's the first time I ever did something like that and I was reling only on some internet research, some youtube videos and some previous experience with the tools I used.

To make a long story short, the first step was to erect the ridge pole which is a 14 foot long piece of 2 by 6. Then, each 2 by 4 rafter is put in place on 24 inch centers and secured both to the ridge pole on top and the wall's top plate on bottom. A strip of 1/2 inch plywood was secured along each side of the ridge and another strip of plywood run along the bottom edge of each side of the roof. This plywood serves as an attachment point for the glazing and to hold the roof square.

The rafter tails overhang the walls by one foot. The facia and soffit are dressed in 1/2 inch plywood. 

The roof and walls are all dressed in purlins which are the horozontal members that are used to support the glazing and serve as an attachment point. They are made from 8 foot long pieces of 2 by 6 lumber ripped down into 3/4 inch strips. This method is way cheaper than buying the strapping from the store. All that was needed was a table saw and some patience.

Finally, corner braces were added to each corner of all four walls for a total of 16. These are necessary to hold the structure stiff and square since there is no sheeting to handle that task. The ridge pole was also supported by a diagonal brace on each side to help hold the roof square. The final structure is as stiff and solid as a rock.

Step 7: Openings for the Doors and Exhaust Fans

Some accomodations were made in the framing for the openings for the exhaust fans, the louvre doors, and the person door.

Each opening was trimmed around the edges with the 1 1/2 inch by 3/4 inch strapping used for the purlins. This is so that the edges of the glazing can be secured to the trim.

Step 8: Painting

Now everything needed to be painted, mostly for aesthetics but aslo to protect the wood from exposure to sunlight and water. There's not much to report here. I just grabbed a bucket of paint and a brush and got going.

To save time and sanity, a paint and primer in one was used. It was a little more expensive but well worth it. In all, a little over three gallons were used.

Step 9: Adding the Glazing

The final step to completing the construction phase of the greenhouse would be to add the glazing. The glazing material in question is 8mm twin wall polycarbonate panels. A really good feature of these panels is that they have a bunch of cells that each have a small air space and provide a good degree of thermal insulation. I'm going to try to take advantage of this insulation to stretch the growing season as long as possible and maybe even all year. The panels are strong too. The manufacturer braggs that the panels are something like 25 times stronger than glass and 5 times stronger than acrylic and built to withstand golf ball sized hailstones.

Unfortunately I couldn't install the panels this season because of the nasty weather. As soon as I was done painting the greenhouse I had the concrete slab for the garage poured so I had to concentrate on building that. Constant wind and rainstorms diring the construction of the garage set my schedule back so far that by the time I was finished it was too cold out to use the caulking necessary to install the panels.

But for the time being, I have much to work on indoors such as:
  • The climate monitoring and control system. Based on the Arduino mega I got for Christmas and a whole bunch of sensors and devices.
  • The vertical garden. A modular configuration of hydroponic grow tubes stacked vertically. It will be able to hold up to 72 small plants. The whole thing will be built in my workshop and transported and installed as a unit (hence the modularity). Once a couple of plumbing connections are made it should be ready to go.
  • The main components of the large grow tubes such as the grow tubes themselves and the micro sprinkler irrigation systems that will go inside them.
  • A solar thermal collector so that I can produce and store hot water in the daytime and use it to heat the greenhouse in the night time.
  • Plus more!
This article will be expanded as soon as the glazing is installed but I guess that's it for now. I hope you enjoyed the read and please stay tuned for updates and related articles. Maybe you could even subscribe! Cheers!