Greenhouses are an excellent growing solution to address unpredictable weather, short growing seasons, and other threats to a healthy garden. Luckily, it is relatively easy to create your own customized greenhouse that fits both your size and budget needs. Greenhouses vary from small raised beds to full-sized complex structures, so there is a solution for everyone – once you have the information to decide what kind of greenhouse you need.
Factors to Consider
There are many factors to consider (besides size and budget) that you may not be aware of. However, these factors can have a huge effect on the efficiency of the greenhouse as well as its legality.
In some towns and cities, you may not actually be allowed to build a greenhouse structure, or you may not be able to build a greenhouse without a specific permit. Greenhouses are often classified as outbuildings, similar to a shed, garage, or pool house, and are not universally allowed in all developments. If you live in a neighborhood or area with a Home Owners Association, you may need to get explicit permission from the HOA before building. Many HOAs do not allow outbuildings at all, so check before you start building.
Location and Sun Orientation
Greenhouses don’t work without being properly exposed to the sunlight. Ideally, a greenhouse should be positioned in such a way that it will receive at least six hours of uninterrupted sunlight per day. If possible, the longer sides of the greenhouse should face east and west, respectively, to maximize the total amount of sun that the plants get year-round. You will want to find a spot that has ample sunlight and good drainage (or else create a drainage system, if that is an option) to ensure the maximum effectiveness of your greenhouse. If you will be using a hose or other attached water system to irrigate your plants, ensure the greenhouse is within easy reach. Likewise, if you will be using an electric heater, lights, commercial exhaust fan, paint booth exhaust fan, or other appliances with electrical needs, make sure that you have access to a working electrical outlet.
Does Your Greenhouse Need a Foundation?
It is not necessary to pour a foundation for the greenhouse, but it can may be a good idea for certain types of greenhouses. One of the main benefits of a greenhouse foundation is that in very cold climates, greenhouse structures may sag or otherwise become compromised due to the freezing and dethawing of the ground every year. A foundation with frost-free footers provides a stable base that prevents this kind of shifting and sagging, protecting the structure of the greenhouse. This is also important if your back yard doesn’t have stable ground in general.
However, once a foundation is built, it cannot be moved. Foundation-less greenhouses are more portable and can be moved depending on crops, seasons, or changing sunlight. Greenhouses both with and without a foundation will work just fine, but which is better for your back yard depends on the climate conditions of your area and your budget. Gravel, bricks, and landscape fabric are options for less-expensive and more portable materials that drain well if a permanent foundation isn’t an option.
Whether you’re thinking about the foundation, the floor, the glazing, or the frame, the materials of nearly any aspect of your DIY greenhouse can be adjusted to meet the needs of your back yard. Here are a few things to keep in mind when considering which material to purchase for the various components of your new greenhouse.
There are a few options to build a greenhouse frame. Which frame is appropriate also depends on what the rest of the greenhouse is made of, because strength needs will vary. Wood is one of the least-expensive and easiest to work with, but may not be suitable for larger greenhouses. Even from a kit, wood can be easily adjusted with a few power tools and a bit of know-how, whereas metalworking is much more specialized. However, metal is also much more durable because it won’t naturally rot over time. Aluminum is a good middle-ground for a relatively lightweight and inexpensive metal that resists corrosion.
Glazing refers to the transparent part of the greenhouse that allows sunlight to filter through. Glazing materials vary depending on need and budget, so there are many options to choose from. Traditionally, greenhouses are glazed with glass, but glass can be heavy, expensive, and delicate, so it may not always be the best option for a DIY or hobby back yard greenhouse. Other options for glazing include fiberglass, polyethylene sheets, polycarbonate, or acrylic, which are all less expensive and less fragile.
There are many options for greenhouse flooring (including leaving the floor completely bare). Concrete is durable, but it can be quite expensive to pour and doesn’t drain well in wet climates. If the greenhouse is located in an area surrounded by trees with aggressive root systems, the roots may also crack and break up the concrete over time. You can leave the floor as plain dirt, but this may not be a good option if you live in a rainy climate or have a high water table because it will get very muddy. For drier climates, a plain dirt floor is the least-expensive and easiest option. Gravel flooring is a great middle option, because it drains well and cannot be damaged by root systems (just add more gravel).
For the less-handy or convenience-orineted greenhouse builder, there are countless greenhouse kit options.
In cold climates, just the greenhouse effect may not be enough to keep the plants safe and warm. Likewise, extremely hot climates may actually cause the temperature to get too high within the greenhouse and result in harming the plants inside. For extremely cold climates and seasons, consider installing an exhaust fan or different fan type along with an electric heater to circulate warm air around the greenhouse.
For hot or mild climates, less drastic measures can be utilized. For example, adding shade or opening rooftop vents and windows can help the heat from becoming too stifling for the plants in the summer. For only moderately cold climates, there are many less involved tricks to maintain a warmer temperature during the night. For example, leaving barrels of water in the greenhouse to warm during the day and slowly disperse warmth during the night is an easy and inexpensive option for more mild winters.
While it isn’t absolutely mandatory to install a water system in your greenhouse, it can make the greenhouse experience much more efficient and easier in the long run (especially for large greenhouses with a lot of plants). You can build your own water system from scratch, but if you have a relatively simple greenhouse layout, you can buy ready-made greenhouse water systems online or in a local gardening or home improvement store. For an extremely DIY option, you can take an old hose, poke holes for water to leak out into the plant pots or beds, and snake it through the greenhouse.
Plants to Grow
Many types of plants can flourish in a greenhouse setting, whether you’re considering herbs, vegetables, flowers, fruits, or specialty plants like cacti and bamboo. All of these plants can benefit from the protection and temperature regulation that greenhouses offer, but the driving factor should be the reason that you are building a greenhouse in the first place. If you want to spice up your home cooking, grow herbs and vegetables that you use in the kitchen and can pick straight from the back yard. If you are selling the plants, profitability should be the driving factor. That said, here are some plants in each category that may do well in greenhouses:
- Herbs like basil, cilantro, oregano, parsley, thyme, and mint
- Vegetables like lettuce, peppers, broccoli, cucumbers, cabbage, peas, and tomatoes
- Fruits like berries, grapes, citrus (lemons and oranges), and peaches
- Flowers like petunias, roses, violets, salvia, and geraniums
How to Build a Greenhouse from a Kit
When you purchase a greenhouse kit, all of the needed materials and pieces are already provided for you. While this limits the ability to customize, it is an excellent option for anyone who doesn’t already own a lot of tools or who doesn’t have extensive carpentry knowledge. When building from a kit, take inventory before starting to ensure that you have everything needed and that nothing is missing. Some kits require you to have some of your own tools, so double-check which tools or other materials (like scissors) you may need on hand before choosing a kit that is appropriate for you skill level. Detailed instructions will come with the kit, so it may be good to read through them a few times before starting to make sure you have a solid understanding of the construction process and to help avoid confusion down the road.
How to Build a Glass Greenhouse
Glass is one of the most popular materials to glaze a greenhouse, but there are a few things to keep in mind to ensure that you are working with the glass in a safe manner. You will want to set up the frame and then raise the glass into place from the ground. Because you may need to the cut the glass to ensure that it fits correctly into place, make sure that you are working with safety glass that will not shatter into large, jagged pieces. Additionally, choose glass that is not made to filter out sunlight, because the whole idea of a glass greenhouse is to capture as much sunlight as possible.
How to Build a Wooden Greenhouse
While wood is one of the most flexible and least-expensive options, there are a few things to keep in mind when building with wood. High heat and humidity within the greenhouse can promote the faster rotting of wood, but some types of lumber (like cedar) are more resistant to these conditions than others. That said, wood can be an excellent choice for dry, hot climates. You can also purchase wood that is treated for outdoor use to help extend its lifespan. If you are also using wood in the foundation, choose a type of lumber rated for ground contact, or it may rot quickly and compromise the structure.
How to Build a PVC Greenhouse
PVC is an excellent framing material for a greenhouse because it is lightweight, inexpensive, and more resistant to the elements than natural materials like wood. PVC may not be durable enough for the weight of large or glass greenhouses, but it can be a great option for smaller greenhouses. You may want to look into UV-resistant PVC to help the frame last longer in rough outdoor conditions, but it isn’t necessary. PVC greenhouses are usually paired with polyethylene sheets due to the lighter weight.
If you plan to move your PVC greenhouse, you can use temporary fasteners like zip ties and bolts to make a structure that is easy to disassemble and move later on. Otherwise, screws or PVC glue are durable options for a more permanent structure.
How to Build a Mini Greenhouse
If you’re only growing a handful of relatively small plants, you can build a mini greenhouse just large enough for the flower bed it covers. Mini greenhouses can be made with recycled windows and a simple A-frame design. Wood or PVC are great options for a mini greenhouse, depending on available tools and aesthetic preference, and you can build a hinge system in the top or side of the mini greenhouse for easy access to the plants inside.
No matter your motivations for wanting to build a greenhouse, there are options available for the humblest beginner and the most advanced carpenter. Regardless of the style, size, and materials you end up choosing, we hope that our guide was helpful in narrowing down your options.