Everything You Need to Know Before You Build a Greenhouse

At first glance, greenhouses may not seem like a necessity as far as backyard projects go. But on closer inspection, they have a lot of compelling benefits. If you happen to be a gardening enthusiast with a backyard full of leafy greens and homegrown spices, you should consider building a greenhouse. These climate-controlled structures are great additions to any garden for a variety of reasons. For one, having all your prized plants in a warm environment means you can grow your crop year-round. A greenhouse makes all the snow, frost, storms, and sudden temperature changes of the natural world irrelevant. There’s something to be said for the peace of mind that comes from knowing your plants are no longer at the mercy of mother nature’s caprice. 

If you’ve always dreamed of growing some zesty pineapples, but couldn’t because you’re trapped in a temperate climate, a greenhouse may just be the answer. Building a greenhouse gives you a much wider range of possibilities as far as what you want to grow. The greenhouse’s hot and humid environment allows you to grow all manner of tropical delights. As a bonus, the hermetic nature of the greenhouse keeps your juicy crops safe from pests. And as National Gardening Month (NGM) rolls around, there’s no better time to build a greenhouse. 

Why You'll Love Having Your Own Greenhouse

While these advantages may be quite persuasive, you likely still have some important questions to ask. Namely, how much will a greenhouse cost? What if I have a small garden? Should I buy or build a greenhouse? Will I need a permit?

If so, you’ve come to the right place. In this article, we will cover these questions and more so that you know everything there is to know before building your own greenhouse. 

How Small Can Your Greenhouse Be?

How Small Can Your Greenhouse Be?

When it comes to small greenhouses, there aren’t any fixed benchmarks. Generally, the most popular dimensions for a “small” greenhouse are 6x8 feet. That gives you 48 square feet to play around with, which is plenty for most people’s needs. You should have enough room in a greenhouse of this size for all the plants and vegetables you would want. Because this is such a popular size for greenhouses, there are a lot of options available in terms of construction materials and size. If you need something smaller, 6x4 greenhouses are also an option. There are also hoop houses, which are usually around 4 feet high and 10 feet in length. Hoop houses present a more compact alternative to a full-size greenhouse, and as such are better for those with limited garden space. 

Mini Greenhouse Ideas

If you need something even smaller, there are also mini-greenhouses. These are small boxes or shelves covered in transparent material. They work the same as a normal-sized greenhouse but are too small to walk into. Instead, mini-greenhouses are usually accessed by zipper doors or lids. These are a great option if you have a tiny garden or no garden at all and want. A larger mini greenhouse will be about 40” x 20” x 60”. 

Greenhouse Ideas for Any Size and Space

How Much Does it Cost to Build a Greenhouse in Your Backyard?

If you hire a licensed greenhouse contractor to build you a greenhouse in your backyard, it will cost you around $14,000 on average. It is possible to have one built for much cheaper. For instance, a small 100 square foot greenhouse built with a wooden frame and polyethylene or glass siding can be built for as little as $1,000. Of course, this assumes that you won’t be installing any HVAC systems or artificial lighting in your greenhouse. More advanced greenhouses cost around $25,000 to construct. A greenhouse of this price will be much larger at around 750 square feet and will be made with more expensive materials like polycarbonate, fiberglass, and steel. High-end greenhouses also feature concrete floors which prevent erosion and are gently sloped to keep water from pooling. Installing a climate control system and plumbing will cost at least $8,000. 

What You Need to Know To Build a Greenhouse

Many local governments require permits to build a greenhouse. If this applies to you, you’ll need to spend an extra week or two going through the permitting process. The cost of a greenhouse permit varies depending on where you are, but costs at least $1,500 in California. If you plan to build your own greenhouse you can cut down on the cost quite a bit. Using simple materials like reclaimed wood, PVC, and plastic sheeting you can build a backyard greenhouse for just $165! The beauty of a DIY greenhouse is that you can design it to be as affordable or as pricey as you want. A homemade greenhouse can therefore be a lot more flexible to design and build, and it’s a great option if you don’t need something very complex. 

Advantages of Building Instead of Buying a Greenhouse

Advantages of Building A Greenhouse Yourself

Greenhouse kits tend to be more expensive however than building your own. The cheapest greenhouse kit goes for around $2,500, and the most expensive kits can cost as much as $35,000. Greenhouse kits also come with some other caveats. The biggest drawback of a greenhouse kit is the lack of customization. Because a kit consists of a premade design, you don’t have much latitude to make changes to greenhouse plans. You have to make do with what the kit provides for. While it is possible to order a kit tailored to your requirements, this will inevitably increase the price. 

By contrast, the design of a built greenhouse can be changed throughout the construction process. You might decide that you want the pitch of the roof lowered, or realize it would be better to move the greenhouse’s door to another side. A contractor can work with you to make these changes to a greenhouse while it is being built. This can’t be changed as easily when assembling a greenhouse kit. Greenhouse kits do have one major advantage which will matter to some people, and that’s time. It will take at least four weeks to get all the materials in place you need for your built greenhouse, and there can be additional wait times for permits and delays. A greenhouse kit can be shipped to you in as little as a week.  

What Materials Should You Use for Your Greenhouse?

What Materials Should You Use for Your Greenhouse

What materials you end up using to build your greenhouse depends on what you want from your greenhouse and how much you’re willing to pay. When it comes to siding, greenhouse glass is a great choice if you want something affordable($2.50 per square foot) and durable. Glass is heavy, however, and will need a stronger frame to support it. Glass is also prone to burn plants when the sun is at certain angles. Polyethylene is the cheapest material you can use at just 12 cents per square foot, but it isn’t very durable. In general, you can expect to replace polyethylene siding every three years or so. 

Polycarbonate siding offers you the transparency of glass but can better disperse light so it won’t cause burning. It’s also cheaper than glass at $1.72 per square foot. Fiberglass is a great choice if you want something more durable and more flexible. It’s also one of the cheapest materials at $1.50 per foot.

As far as framing goes, you have the choice of wood, aluminum, or steel. Wood is usually cheaper at just $1 per foot, whereas steel and aluminum are more than double that price. The tradeoff here is that a metal frame will have more structural integrity, and will be able to support much more weight. Metal frames are also more durable and will have lower long-term maintenance costs than wooden frames. If you want to build a bigger greenhouse using heavier materials like glass, getting a metal frame is a worthwhile investment.      

Bonus Tips

• Foundation: All walk-in greenhouses will need some form of foundation to help support their weight. Greenhouses of this size are really like miniature buildings, and will similarly need concrete foundations with proper drainage. So take some time to design your foundation. You don’t want to spend the time and money to design and build a greenhouse only to then have foundation problems.
• How big the door is: You should also think about the size and placement of your greenhouse’s door. You want the door put in a place where it won’t be blocked by plants or debris so that it can be used safely. Your greenhouse’s entryway should also be big enough to fit through whatever equipment (wheelbarrows, watering cans, rakes, hoes, etc.) you’ll need.