How to Build a Greenhouse in 8 Steps

Greenhouses are a great way for homeowners to grow veggies and ornamentals all year round. If you’ve ever wanted a greenhouse for your property, look no further. It’s as easy as one, two, tree if you follow our step-by-step guide on how to build a greenhouse.

Tools and materials

The tools and materials required to build your own greenhouse can depend on the type of greenhouse you want to make. However, these 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. There are many greenhouse design plans available online, but you can also draft your own. You can also buy a DIY greenhouse kit or even 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 greenhouses. They’re typically attached to the side of a house and can only house a few small potted plants, like herbs. These small greenhouses don’t have a heat source.
• Attached greenhouses, as their name suggests, 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 that 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 greenhouse 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 quite strong.
• PVC pipes: PVC pipes are the cheapest framing materials, but they’re also the least durable ones. Make sure to choose UV-resistant pipes so they last longer.
• Wood: Wood is charming, but untreated timber will rot in damp environments. Make sure to use treated wood, but take note of the type of treatment used; some wood treatments aren’t food-safe. Some types of wood 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. 

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 going with clear plastic film for your greenhouse cover, consider low-density polyethylene (LDPE), which is more expensive but is non-toxic and lasts longer. Greenhouse plastic will need to be replaced every few years.

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, you can go with acrylic (Plexiglass), which lets more light through but is not as durable.

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 will probably need to replace it if you’re worried about aesthetics. Over time, fiberglass turns yellow and cloudy.

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, you can 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.

You’ll want to position your greenhouse facing south or southeast so that it gets the maximum amount of sun exposure, even in the wintertime. 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, you’ll need to prepare the site. There are two ways to prepare the greenhouse site. You can add gravel or some other form of weed barrier (or both), or you can build a foundation.

No foundation

If the site where you plan to build your greenhouse has uneven ground, you’ll have to level it. Usually, this means adding topsoil and evening it out with a rake. If you’d like more detailed instructions, you can 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. 

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, you’ll want to place your foundation below the frost line to keep your plants warm during the colder months.

Make sure the ground is level. Then, lay down a foundation that’s slightly larger than the base of your greenhouse. You can pour concrete or build a wooden foundation. If you’re going with a wooden foundation, make sure to use contact-rated, pressure-treated timber.

You should 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 that 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. Make sure to seal your covering to the frame with sealant or studs as closely and as securely as you can. 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 nasty things 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, you should strongly consider a greenhouse heater of some sort. Electric heaters are the cleanest option, but you’ll need a source of electricity. Wood-based or oil-based heaters won’t need an electric source, but you’ll need to vent the smoke outside. Learn more in our article about how to heat a greenhouse. 

Highly recommended: Create raised beds

There are many benefits to raised bed gardening, such as good drainage and better accessibility – no need to bend down so far to water your plants! They can even make your greenhouse look prettier, too. If you’re building a foundation for your greenhouse, you’ll most likely need to make raised beds.

Check out our step-by-step instructions to build a raised garden bed if you choose to add this step to your process. 

FAQ about building a greenhouse

How much does a greenhouse cost?

On average, a professionally built greenhouse costs $11,000. However, the cost of a greenhouse can range between $2,000 and $25,000.

DIY greenhouses typically cost around $5,000, but you’ll be paying in time and effort.

Why should you build a greenhouse?

The main reason why you would want to build a greenhouse is to garden even outside of the typical growing season, as the greenhouse protects your plants from the elements. Greenhouses can also help you maintain specific growing conditions, like a tropical environment for palm trees or birds of paradise. They can also house your tools, doubling as a garden shed.

What’s the best size for a greenhouse?

The most common size for a greenhouse is 8 by 6 ft, but you can definitely go larger or smaller. The best size is the size that fits your needs; you can go with a big or mini greenhouse. However, you should try to maintain a 1:3 size ratio.

Do you need a permit to install a greenhouse?

It depends on the area. While most small residential greenhouses probably won’t require any special building permits, it’s best to consult your local zoning office.

When to hire pros to build your greenhouse

Building a greenhouse takes a lot of work and planning, and you might run into problems if it’s built incorrectly. If you’re poring over the specifics when you’d rather be pouring love on your plants, consider hiring a contractor to build your greenhouse for you. And if you would rather admire your beautiful garden without getting your hands dirty, you can hire a local gardening pro to do all the work while you sit back and enjoy the view. 

Lawn Love can connect you with small lawn care and landscaping businesses in your area who offer services like gardening, lawn mowing, weed control, fertilization, seasonal cleanups, and more. Get a free quote today through our online platform and unlock your garden’s full potential!

Main Photo Credit: Antema | Canva Pro | License