7 Things You Need to Know Before Buying or Building a Greenhouse

Choosing the right greenhouse isn’t just about picking something cheap or small—it’s about setting yourself up for long-term success. While a DIY project might seem like a good idea, a flimsy structure can easily collapse in a storm, costing you more in the end. If you're serious about greenhouse gardening, it’s important to take the time to define your goals and understand your needs. Only then can you choose the right greenhouse to match your vision, resources, and future growth.

Here are 7 things you need to know before buying or building your greenhouse, and why each is crucial—but often overlooked.

 

1. Choose the Right Size for Your Needs

What You Need to Know: The size of your greenhouse matters more than you think. A small greenhouse might be a good idea for beginners or those with limited outdoor space, but it can quickly become too cramped. On the other hand, the largest greenhouse might be too costly or challenging to maintain.

Why It's Necessary: You need enough space for your plants, tools, and a heating system while leaving room to walk and work comfortably. Think about your long-term goals, whether you plan to grow citrus trees, start seeds, or cultivate exotic plants and how much time you plan on spending in the greenhouse to add certina levels of comfort like a small working area or a large work table with seating. 

Why It's Overlooked: New greenhouse owners often underestimate how much space their plants will need, overlooking not only how small plants grow into larger pots but also the vertical space that often goes unused, which could otherwise support climbing or hanging plants.

2. Understand Your Climate and Its Impact

What You Need to Know: The local climate will significantly influence your greenhouse needs. For example, during colder months, a cold frame, lean-to greenhouse, or one equipped with temperature control is essential. In hot climates, adding evaporative cooling systems can help combat excessive heat and maintain ideal growing conditions.

Why It's Necessary: The greenhouse's role is to maintain ideal conditions regardless of the outside temperature—ensuring a reliable heating system during the winter months and efficient, easy-to-run ventilation and cooling systems in the summer months.

Why It's Overlooked: Many underestimate how much heat loss or high temperatures can affect their plants, especially tropical plants or seedlings with specific germination rates. This is why a greenhouse built to withstand temperature fluctuations and tailored to your climate provides a strong start for your plants.

3. Find the Best Spot for Your Greenhouse

What You Need to Know: The perfect place for a greenhouse offers plenty of light and protection from bad weather. As a rule of thumb, it should face south or southeast to maximize natural light while being shielded from strong winds.

Why It's Necessary: Your greenhouse needs full sun exposure during early spring and late autumn to thrive, reducing energy use and making it more self-sufficient and cost-effective. Poor placement can result in inconsistent internal temperatures, low light levels, poor plant growth, and unnecessary expenses.

Why It's Overlooked: New greenhouse builders sometimes prioritize convenience over light availability, leading to inefficient results; however, conducting simple tests to find the best spot with optimal daylight and less wind exposure can make a significant difference.

4. Consider Your Foundation Options

What You Need to Know: A greenhouse can be built on bare ground, native soil, or a concrete slab, but keep in mind that a solid foundation helps prevent structural damage and improves insulation.

Why It's Necessary: The foundation impacts drainage, heat retention, pest control, structural stability, and long-term durability. Without a solid base, water pooling or uneven settling can compromise both the structure and the health of your plants.

Why It's Overlooked: DIY greenhouse builders might skip this step for simplicity, but a simple solution like gravel or treated wood can make a huge difference. For permanent structures, invest in a concrete foundation and if it's an addition to the house, consider adding a ground heating system. This can help maintain a consistent temperature, making the greenhouse a comfortable, year-round space—almost like a small tropical paradise to relax in.

5. Plan for Temperature and Humidity Control

What You Need to Know: There are many temperature and humidity controls available to help manage your greenhouse, suited to different needs and budgets. Options range from electric heaters, heat mats, and hot air systems in colder climates to fans and vents for ventilation. It’s important to choose systems based on the specific usage and plans for your greenhouse.

Why It's Necessary: Maintaining the right internal temperature is crucial for your plants. Overheating or excess moisture can damage seedlings, lower germination rates, and increase the risk of diseases while humidity can promote mold, root rot, and other plant diseases.

Why It's Overlooked: Many people assume a greenhouse naturally maintains a warm environment, but this isn't always true. 

6. Assess Your Available Space and Future Needs

What You Need to Know: The available space in your yard or outdoor garden will determine whether a freestanding greenhouse or an attached greenhouse is feasible, as well as the activities you plan to do there. Consider whether the greenhouse will primarily be used for gardening, or if you’ll be gardening and transplanting plants. If you’d like a small area to relax, it’s important to factor in additional space for pathways, storage, and potential future expansion.

Why It's Necessary: Your greenhouse should fit comfortably into your outdoor space while leaving room for other uses. For example, hobby greenhouses are ideal for small spaces, while freestanding greenhouses are better suited to larger properties.

Why It's Overlooked: It’s easy to focus solely on the greenhouse itself without considering how it fits into your yard. Careful planning of your layout is essential to avoid wasting valuable square feet and to ensure efficient use of your outdoor space.

7. Factor in Your Budget and Long-Term Goals

What You Need to Know: Greenhouses range from affordable high tunnels with clear plastic sheeting to high-end traditional greenhouses or side-leaning frames attached to the house. The choice depends on your needs and budget.

Why It's Necessary: Investing in the right structure ensures your greenhouse lasts for years and suits your goals, whether it’s growing citrus trees, extending the gardening season into colder months, or creating a space for hobbies or workouts.

Why It's Overlooked: It’s tempting to choose the cheapest option, but poorly built greenhouses often fail in cold weather or high winds, leading to a bad investment. A good choice balances cost, durability, and future expansion.

Final Thoughts

Building or buying a greenhouse is a big investment, but it requires careful planning. Once you have a clear idea of your gardening goals take the time to plan your greenhouse accordingly. A well-designed structure will help your plants thrive and turn your garden into a productive, efficient space.