In 2014, I designed and built a backyard lean-to greenhouse for my clients. They needed to replace their deck but decided to put a greenhouse there instead. As you can see from the image, my clients also wanted a space to entertain guests in the backyard.
The goal was to see how much food we could grow in this greenhouse and whether it would last the harsh Canadian winter. We will go over the design and construction process step-by-step, so you can go about making your own greenhouse. This was an east-facing greenhouse that got great morning sun. There were, however, many challenges to this greenhouse, and we go over the solutions I devised at the end of this post.
The greenhouse design
1. Cedar structure
The greenhouse structure was made out of cedar. We did this for the longevity of the wood and the fact it is food grade. Cedar also protects against different types of insects, so that was another benefit.
Everything was built to standard building sizes of 16″ on centre, rafters, and a 2% sloped roof on the top. The total height was just over 6′ on the inside. This was fine as the clients were short in stature and could easily stand in there.
2. Polycarbonate Siding
We chose to use polycarbonate siding on the greenhouse as it was lightweight, durable, and insulated the space. Working with this material was easy, but we needed an air compressor to make sure we could clean out the insides from the cuts we made. To cut this, we used a skill saw and turned the blade around.
To fasten the siding to the wood structure, we used special screws with rubber washers. This prevented water and air flow front entering the green house. We also made sure we used silicone in areas that connect to the roof to have a more of a tight seal.
3. Ventilation
We installed two temperature-controlled window opener vents in the greenhouse. One of the main reason for the two vents was that it would enable have air flow going through the green house if it got too hot.
We also installed one of the window vents upside down. This was done as it was a small space, and it could heat up easily and quickly. To make sure the hot air got out of the greenhouse fast, it was important to have the vent as close to the top of the greenhouse as possible. To make sure water wouldn’t fall into the greenhouse, we extended the roof cover.
4. Rain catching
The eavestrough ran along the greenhouse and down under the stairs, where it was connected to a rain barrel system. This system was used to water the plants of their backyard.
5. Double door entry
The greenhouse was off the back door to the house. We wanted to ensure that this door could be used regularly but also not affect the temperature of the greenhouse. To do this, we installed a door to the greenhouse as well as another door to the backyard.
This was they could come in and out of their home easily and also go into the greenhouse without loosing a lot of heat to the outside temperature.
6. Insulated floor
The floor of this greenhouse was insulated, as it was above a basement apartment. We wanted to make sure that cold air wouldn’t come in from below during the winter. I added a sloped floor with roofing tar roll and had water drain to the door area in the front. This was to make sure you would not have to worry about watering your plants and have all the extra water drain out.
7. Extra places to grow
Since their home was in an urban setting, it was crucial to use the space as best as we could to grow food. On the north side of the property, we had some extra space near the benches and belt, an area for beans and other climbing crops. Used a 4″ × 4″ mesh for the plants to climb up.
On the south side it of the property, we installed a raised-raised bed! On the top of the fence, we put another spot to grow food. It ran the full length of the backyard and was a great spot to really grow full sun-loving crops!
8. Light sensor
On the outside, we installed a light sensor that controlled the lights of the greenhouse and stairs. This was to make sure when the light got low enough, we would get extra growth in the greenhouse. The grow lights that we used are T5 fluorescent lights that ran the extent of the growing space.
9. Shading cloth
At the height of summer months, this greenhouse got hot — almost too hot to grow things inside. You know, just one of many wonderful challenges of growing food in the Toronto climate, too cold in the winter and too hot in the summer. To combat this, we installed a retractable shading cloth that would cover the whole greenhouse when necessary.
10. Growing beds
The growing beds were made out of 1 × 6 cedar planks. The bottom one was one tier tall, while the top one was two. The idea was they could grow leafy greens on the bottom and larger crops on the top, like peppers.
The wood was lined with pond liner to keep the water in. We laid stones on the bottom so a water reservoir could be formed, and lined that with a nylon mesh to keep the dirt out of the reservoir. Finally, we used a compost mix for the soil.
What we learned from this build
Well let’s start by saying it was a great honour to have such an amazing project in the heart of Toronto! It was a project that made me think about all the ways we can really use the available space in the city to grow 21st century victory gardens.
- Climate control. All the things that are needed to keep the ideal temperature of a greenhouse all year round.
- Pest control. We started to get pests in the greenhouse, from aphids to slugs. We would put diatomaceous earth on top of the soil, copper around the entry points, lady bugs, washing the plants — you name it we tried it. Might even do a post on all the things that we went through to find a healthy balance.
- Great clients. Really, having people that want to be part of your vision is so important. These homeowners wanted to see what was possible with everything. They were amazing to work for.
