To Build a GreenHouse

Winter is coming and our succulents need a protective home. Also, we want to continue to grow vegetables despite the cold. The solution was a greenhouse. A quick check of the prices of commercial greenhouses was a little shocking. We saw small 6’x8′ greenhouses for $2500! The one we wanted needed to cover around 25′ and commercial units were close to $10K! What’s a guy to do? Internet to the rescue.

I saw lots of people putting up low cost greenhouses using PVC pipe as the main “skeleton”. Most of the ones I saw were simple and people made due with whatever parts they had. They boasted of building their houses for $50. Well, I needed something a bit nicer and also something that I could disassemble if needed. This is the story of how I built our 25′ long by 9′ wide by 8′ tall greenhouse.

I started with a base using 2″x 6″ pressure treated lumber. Putting 3 x 8′ foot pieces end to end gave me 24′. That was going to be the size of our green house. I simply used a 2′ piece with screws to tie the 8′ boards all together.

Pressure treated lumber is used for ground contact areas.

Next up was building the ends of the greenhouse. I wanted to have large 3.5′ x 6′ doors on both ends so that we could walk through the green house. It’s also great for ventilation. The width was going to be 9′ to fit in the side yard. I used a 9′ board and cut out the opening for the door. At the ends I fastened a 20′ length of PVC pipe in order to get an idea of the shape of the arch. Then around this I build a frame for the door out of 2″x4″ lumber.

The end pieces (2x) with the door cutout.

The ends of the PVC are secured in two ways. First I used a 1″ pipe strap to locate it. Then I used a drywall screw through the PVC to make it immobile. The same idea was used for each of the hoops that form the skeleton of the greenhouse.

Pipe straps keep the frame in place. This is before final assembly and the addition of a drywall screw to keep everything in place.

The ends of the greenhouse was fastened to the sides and the main body was built up all using screws. I used screws because there was a possibility that we would move this green house in the summer. We wanted to make sure that it was possible to disassemble it all if needed. This was one major departure from what I saw online in other plans. Most assume that this thing is never going to move.

A word about the pipes. I used schedule 40 PVC pipe for the ribs. This is just standard stuff you can buy at the sprinkler store. The one I used was 3/4″ internal and 1″ external diameter. This stuff is fairly cheap. For me a 20′ length cost about $7.50. The nice thing is that one end has a “bell” so that it easily slides into the next piece of pipe. Using this feature to my advantage, I had them cut all the pipe in half to 10′ lengths so that it fit in the car. Before assembly, I just friction fit the pipes together to get the 20′ length back and then bent the pipe and secured the ends to form the arch. It was simple and it worked perfectly.

For the top roof rib, I used a bit larger 1 1/4″ pipe and used a drywall screw to fasten it to the joint of the rib. Using this screw served a double purpose. It made the joint immovable because of the screw and it also gave me more pipe material for the screw to bite into. Recall the bell housing with friction fit on top.

To make my greenhouse, I spent $94 on pipe. This was for 9 x 20′ pipes of 1″ and one 25′ pipe of 25′. This was one of the cheapest parts of the project!

Up to this point, it took about 1/2 a day to get to the main frame of the greenhouse. The next trick was to figure out where to get all of the special plastic that would be the skin of the house. As it turned out, that was easy!

Frame built, doors coming next before the skinning.

One thing I should mention is that to make the door frame stiff, I used a 6′ steel fence post. They came pre-painted and I just had to drive them into the ground with a baby sledge hammer and then screw them to the frame.

After some research, I came across the Greenhouse Megastore. Now this place caters to professional growers. I learned that using regular plastic film was a bad idea. It would only last for a year or so with all the exposure. The greenhouse megastore offered a special 6 mil plastic that was treated to be UV resistant, reduce condensation, retain heat and have a light dispersion property. Not only that, their 20′ x 25′ roll was perfect for my application. I would get a smaller roll for the ends of the greenhouse. As for fastening, they had PVC clips that were designed for the pipe size I had used. So I build the doors, painted all the wood and wrapped the plastic on the end frames. I just used heavy duty staples to fasten and then sandwiched the film between wood where ever I could. I was also told that I needed to put something between the PVC and the plastic film since they apparently can damage each other. There was a self adhesive felt that they sold for this. OK, gimme some felt – kinda expensive at $16 a roll and I needed 4 rolls.

Doors in place with a small sampling of the succulents that will live in the greenhouse.

Now came the super tricky part. How was I going to guide and fasten a 20′ x 25′ piece of plastic across the top of the frame? Also, how was it going to fasten to the ground? I thought of a pretty clever solution. 😉

I got some 1″ x 8′ strips of wood at the lumber store. They were precut and came in a bundle of 12. The plan was to sandwich the length of plastic film in these strips at both ends. Then i would roll it up to form a bundle of wood rolled in plastic. Getting some help, I would thread the roll through one side of the green house and then unroll the length of it over the frame.

Laying the plastic film on the driveway and fastening the wood strips to the ends.

No only would this make it easier to handle, but it would also allow me to securely screw the wood strips to the treated base lumber. All this is accomplished without puncturing the plastic where unnecessary and also in keeping with the goal to make is possible to disassemble if needed. So after unrolling and then fastening the sides to the base, here is what I have.

View inside the greenhouse after the sides are secured.

Now the last step was to secure the ends to the plastic side pieces. This was done with the PVC clips. This was remarkable easy to do and allowed me to stretch everything tight before fastening. I was worried that the plastic may rip, but that was unfounded. That 6 mil stuff is strong!

Greenhouse near completion. Building the shelves inside is for next weekend.

So here’s a shot of the near complete greenhouse. I painted the doors and put in some nice gate latches in order to make the doors secure.

So what did all this set me back? Here’s a rough estimate.

1. PVC pipe = $94

2. Wood for frame, base and doors = $220

3. Plastic film and accessories = $224

4. Hardware = $60

So for roughly $600 I have a fairly large greenhouse that is a lot nicer than many of the other quick projects that I have seen out there on the web. It is also a fraction of the cost of “kits” that you can buy; not to mention the fact that most kits are much, much smaller than this one.

So we are looking forward to our first winter with this green house. We have big plans for the various things that are inside already. Besides the succulents, there are peppers, citrus and vegetables that will be grown inside.

We are planning to construct 4 levels of shelves on each side of the green house so it’ll have quite a massive capacity of plants housed inside. We also discovered that we can hang plants from the top center rib, so there are already a few hanging plants in there.

As we complete the interior of this greenhouse, I’ll post some pictures.

This took a few weekends to complete and I think that anyone with the desire can pull it off!

=====< Update on April 10, 2015 >=====

Well the plants made it through the winter with flying colors. The greenhouse residents (plants) continue to grow and I have added places to hang plans as well as overhead lights so that my wife can work in the greenhouse at night.  Everything has worked out well. Here’s an interior picture where you can see how the shelves greatly increase it’s capacity. This was before the lights and the table and chairs that are in there now.

The greenhouse is packed for the winter.