Greenhouses are a great way for homeowners to grow veggies and ornamentals all year round. How to build a greenhouse may seem daunting, but it’s as easy as one, two, three if you follow our step-by-step guide. If you’ve ever wanted a greenhouse for your property, look no further. How to build a greenhouse starts with understanding the tools and materials needed and continues with selecting the right design, framing, and covering materials. Let’s dive into how to build a greenhouse and turn your gardening dreams into reality.
Tools and Materials
The tools and materials required to build your own greenhouse depend on the type you want to make. However, here are some common tools and equipment needed for these projects:
- Framing materials
- Covering materials
- Basic hand tools
- Safety gear
- Drill
- Impact driver
- Framing nailer
- Level
- Miter saw
- Sawhorse
- Table horse
- Scissors
- Landscape fabric
- Gravel
- Concrete (if building a foundation)
Step 1: Decide on a Greenhouse
There are many types of greenhouses that you can choose from—different styles, shapes, and sizes. You can find various greenhouse design plans online or draft your own. You can also buy a DIY greenhouse kit or convert an old structure into a greenhouse.
One of the most important things to consider is if your greenhouse will be a standalone structure or an attached one. Consider these options:
- Cold-frame greenhouses are the smallest and simplest. Typically attached to the side of a house, they can only house a few small potted plants, like herbs. These small greenhouses don’t have a heat source.
- Attached greenhouses are attached to an existing wall, like a house. They’re bigger than cold-frame greenhouses and typically have a heat source. They can usually share electricity with the structure they’re attached to.
- Standalone greenhouses are freestanding structures. They’ll need an electrical connection and heat source if they’re not close to an existing structure.
Step 2: Choose Your Framing Material
A greenhouse frame has to be sturdy to withstand high winds and the general weight of the structure itself. Homeowners can choose from a variety of materials to frame their greenhouse:
- Aluminum: Aluminum is one of the most expensive materials for a greenhouse frame, but it’s rust-resistant, lightweight, and strong.
- PVC pipes: PVC pipes are the cheapest framing materials but are also the least durable. Choose UV-resistant pipes so they last longer.
- Wood: Wood is charming, but untreated timber will rot in damp environments. Use treated wood, but ensure the treatment used is food-safe. Some woods are naturally rot-resistant too.
- Galvanized steel: This material is typically used by commercial growers. It’s very sturdy, but it’s expensive and can rust.
Step 3: Choose Your Covering Material
Some covering materials go better with certain types of framing materials. Make sure to pick a covering material that’s right for your build. Consider the following options:
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Clear plastic sheeting: Plastics like UV-stabilized polyethylene are lightweight, cheap, and easy to find, but they don’t last. Some plastics also contain BPA, which is toxic and unsafe for growing food.
If you’re using clear plastic film for your greenhouse cover, consider low-density polyethylene (LDPE), which is more expensive but non-toxic and lasts longer. Greenhouse plastic will need to be replaced every few years.
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Hard double-walled plastics: These plastics are more durable than regular clear plastic; polycarbonate is up to 200 times stronger than glass. Most polycarbonate panels contain BPA, though.
If you want a non-toxic option, go with acrylic (Plexiglass), which lets more light through but is not as durable.
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Fiberglass: This material is durable, clear, and UV-resistant, but it’s not cheap. It’s a decent option if you’re building a framed greenhouse, but you may need to replace it if you’re concerned about aesthetics. Over time, fiberglass turns yellow and cloudy.
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Glass: Glass greenhouses are arguably the most beautiful; however, they have their fair share of downsides. Glass is fragile and expensive, even when it comes to repairs. On the bright side, you don’t need to replace it if it’s not broken.
Consider getting tempered or safety glass if you’re worried about your greenhouse breaking—especially if your area gets hail. If you want to save money, look into recycling old glass, old windows, or even old greenhouse panels.
Step 4: Choose a Location
Choosing a location is probably the most important factor influencing the success of a greenhouse project. If you build your greenhouse in a shaded area, don’t expect your plants to grow properly. You also want to pick a place that has access to electricity and soil that drains well.
Position your greenhouse facing south or southeast to get the maximum amount of sun exposure, even in the winter. Placing your greenhouse in the southwest is also an option if you live in an area that doesn’t experience extreme heat.
Make sure you choose a place that doesn’t have many bushes or trees—especially evergreen ones like pines—that can cast shadows on your greenhouse.
Step 5: Prepare the Greenhouse Site
Once you have your building materials, prepare the site. There are two ways to prepare the greenhouse site: adding gravel or some other form of weed barrier (or both) or building a foundation.
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No Foundation: If the site where you plan to build your greenhouse has uneven ground, you’ll need to level it. Usually, this means adding topsoil and evening it out with a rake. If you need more detailed instructions, check out our guide on how to level an uneven lawn.
Leveling the ground is crucial, as uneven ground can lead to pooling water. It’s also generally easier to build on even ground.
Once the greenhouse site is level, lay down a well-draining material that blocks weeds from growing in your greenhouse. You can use gravel, landscape fabric, or bricks. You can even lay down gravel on top of landscape fabric for a double layer of weed protection.
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Foundation: If you opt to build a foundation for your greenhouse, you’ll need to dig out a few inches of topsoil to house it. If you live in an area that gets very cold temperatures, place your foundation below the frost line to keep your plants warm during the colder months.
Ensure the ground is level. Then, lay down a foundation slightly larger than the base of your greenhouse. You can pour concrete or build a wooden foundation. If you’re using a wooden foundation, ensure it’s contact-rated, pressure-treated timber.
Consider building a foundation if you’re using heavier construction materials, such as glass.
Step 6: Construct the Frame
This step will be highly dependent on the greenhouse plan you decide to go with. Follow the instructions included with your greenhouse plan or DIY greenhouse kit.
Step 7: Add the Covering to the Frame
For the most part, continue following the instructions for your greenhouse plan or kit. Ensure you seal your covering to the frame with sealant or studs as closely and securely as possible. Leave space for ventilation and the door.
Step 8: Add Ventilation and Temperature Control
Ventilation is important not just for temperature control but also for proper air circulation, which keeps mold, mildew, and other issues from developing on your plants. Install roof vents (or other vents) and fans to improve airflow. Ideally, they should be adjustable; the fans should also be able to run constantly during the winter months to spread heat out evenly.
For temperature control, consider a greenhouse heater. Electric heaters are the cleanest option, but you’ll need a source of electricity. Wood-based or oil-based heaters don’t require an electric source, but you’ll need to vent the smoke outside. Learn more in our article about how to heat a greenhouse.
