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How to Build a Greenhouse: A Step-by-Step to Build DIY Greenhouse

How to Build a Greenhouse: A Step-by-Step to Build DIY Greenhouse

A greenhouse allows you to extend your growing season and grow plants that normally couldn't survive your climate. With the right design and materials, you can build your own greenhouse that will last for many gardening seasons to come. This comprehensive guide will walk you through all the steps and considerations for planning, constructing, and using your backyard greenhouse.

Key Takeaways

  • Choose the perfect location by considering sun exposure, wind protection, accessibility, drainage, and access to utilities. South-facing with 6+ hours of direct sun is ideal.

  • Build a sturdy foundation at least 1 foot deep to withstand the load and prevent frost upheaval. Install drainage gravel and sand.

  • Assemble the frame using weather-resistant materials like treated lumber, aluminum, or steel. Join pieces securely and add diagonal bracing.

  • Select durable glazing like polycarbonate panels or tempered glass to balance insulation, light transmission, and cost.

  • Add temperature controls like vents, fans, shade screens, and heaters for ideal growing conditions. Automate systems for easier management.

  • Customize the design with amenities like shelves, sinks, storage, and irrigation to maximize space and create your ideal plant environment.

an image of a man building a lean to greenhouse

    6 Steps to Build a Greenhouse

    1. Choose the Perfect Location for Your Greenhouse

    Choosing the right spot to build your greenhouse is one of the most important decisions you’ll make, as it will affect everything from the amount of sunlight your plants receive to how easily you can access the structure. Keep these key factors in mind when selecting your greenhouse site:

    Factors to Consider When Selecting a Greenhouse Site

    • Sunlight: Your greenhouse should receive at least 6 hours of direct sunlight daily, especially during the cooler months when the sun is lower in the sky. An east-west orientation often provides the most light exposure.

    • Wind protection: Shelter your greenhouse from strong winds, which can damage the structure. Build the greenhouse near a windbreak like a fence, trees, or shrubs.

    • Accessibility: Pick a spot that is easy to reach from your home so you can tend to your greenhouse plants conveniently. Allow enough space around the greenhouse for cleaning and moving plants in and out.

    • Drainage: Your greenhouse site needs good drainage to prevent water from pooling. Avoid low spots and grade the soil if necessary so water flows away from the foundation.

    • Utilities: Situate your greenhouse close to available water and power sources for convenience. This makes watering, heating, and lighting systems much simpler to install.

    Ideal Placement for Optimal Sun Exposure

    The best place to set up a greenhouse depends on several factors, such as the climate and environment of the area. Generally speaking, an ideal location should have plenty of sunlight, good air circulation, protection from strong winds and pests, and easy access to water.

    Here are some optimal greenhouse placements to maximize sun exposure:

    • Along the south side of your home or another structure that provides wind protection. This takes advantage of passive solar heating.

    • In an open, sunny spot in your yard that gets sun for most of the day. Avoid shade from trees.

    • On the east side of your property if your backyard faces west. An east-facing greenhouse takes in the morning sun.

    • In a south-facing garden bed area that gets sunlight throughout the day.

    • Against a darkened wall or fence that absorbs heat from the sun and radiates it back into the greenhouse.

    Take note of sun patterns on your property before choosing the perfect spot. Observe the site at different times of day to determine the total sun exposure.

    2. Build the Foundation of Your Greenhouse

    A proper foundation is crucial for any permanent greenhouse structure, as it must bear the weight of the greenhouse and withstand forces from wind and soil movement. Taking the time to build a robust foundation will pay off with a greenhouse that lasts for many years.

    Setting Up the Foundation Frame

    The foundation of a greenhouse is crucial for its stability. It should be able to withstand its own load and the weight of the greenhouse on which it rests. Start by creating a rectangular frame with the exact dimensions of your planned greenhouse using weather-resistant lumber like cedar, redwood, or treated pine. Secure the frame together at the corners using galvanized brackets and screws.

    Bury wood foundation frames are at least 1 foot deep in the ground to protect them against frost and provide stability. If your location has freezing winters, bury the foundation 2 or more feet deep to prevent frost upheaval.

    Pouring a Gravel Floor for Drainage

    A well-drained area is essential for a greenhouse. If your location is uneven, you may need to fill in the area to encourage drainage. Place 4 to 6 inches of gravel within the foundation frame to create a floor that allows water to drain away easily. Paver base gravel offers the best drainage.

    Compact the gravel layer with a plate compactor. Then pour a 2-inch layer of sand over the compacted gravel and flatten it for a smooth surface. The sand will help level any dips and holes in the gravel base. Installing landscaping fabric under your gravel can inhibit weed growth.

    3. Assemble the Greenhouse Structure

    Once your foundation is complete, it’s time to build the frame and enclose the greenhouse space. The main structural components include roof beams, wall framing, side posts, and rafters. Follow your greenhouse plans carefully during assembly.

    Joining the Frame Pieces Together

    The main components of a greenhouse are its structural components like trusses, purlins, and side posts. Most frames are made from steel, aluminum, plastic, or wood. Connect the frame pieces together as specified by your building plans using the appropriate hardware. Ensure diagonal bracing is installed for extra stability.

    For small to mid-size wooden greenhouses, assemble a simple frame using 2x4 or 2x6 lumber. Use metal brackets to connect the lumber at the corners and joints. Wood frames assembled with screws allow more customization and future modifications.

    Aluminum frame kits offer lightness and durability. PVC frames are low maintenance but can be more difficult to modify later on. Steel provides the greatest strength for larger greenhouses but requires precision assembly.

    Attaching the Wall Panels

    The wall panels, often made of polycarbonate, fiberglass, or glass, allow sunlight in while insulating your greenhouse and protecting your plants. Measure and cut panels to size as needed to fit within the frame. Use the hardware recommended by the panel manufacturer to affix the glazing while keeping condensation drainage in mind.

    PC panels offer high durability and good insulation. Fiberglass lets in more light but is not as impact-resistant. Tempered safety glass has the highest clarity but is heavy and prone to breaking.

    Installing the Roof Panels

    The roof glazing materials have a big effect on the internal temperature of your greenhouse. PC panels are easy to work with and provide good insulation. Fiberglass panels transmit the most light.

    Make sure any roof vents and ventilation systems are installed before attaching the main roof panels. Seal all connections with silicone and use rubber washers when securing the panels to prevent leaks. The roof angle will depend on the materials used and your climate, but a minimum slope of 14 degrees allows condensation and rainwater runoff.

    4. Select the Right Covering Material

    The glazing materials used for the walls and roof are what really define a greenhouse and have a major impact on its performance and growing conditions. Take time to select the right covering materials for your needs and budget.

    Comparing Glass vs. Plastic Polycarbonate Panels

    Siding for your greenhouse should be your major consideration since it will affect the cost and efficiency for years to come. Glass and polycarbonate are two of the most popular options:

    Glass provides the highest clarity and lasts almost indefinitely, but has drawbacks like expense, weight, and fragility. Tempered safety glass is a good glass choice for greenhouse glazing.

    PC sheets offer high durability and good insulation at a lower cost, though they can become brittle and discolored over time. Polycarbonate is easy to work with using basic tools.

    There are also multiwall structured polycarbonate panels with air gaps that provide even better insulation for energy savings. Polyethylene film is inexpensive but less durable.

    Pros and Cons of Different Greenhouse Coverings

    No greenhouse glazing material is perfect. Consider these advantages and disadvantages when choosing greenhouse covering:

    Glass: Excellent light transmission, long-lasting, resists discoloration over time. However, glass is expensive, heavy, and fragile. Safety glass is a better option than standard glass.

    Polycarbonate: Affordable, good insulator, impact resistant. Can become brittle with age and eventually discolors. Upkeep is required to clean.

    Fiberglass: Transmits the most light for optimal plant growth, a decent insulator. Not as impact-resistant as polycarbonate and is more expensive.

    Polyethylene film: Low-cost material, easy to install. Can tear easily, degrades over several seasons, and allows less light through. Best for temporary structures.

    Rigid plastic (PVC, acrylic): Much stronger than polyethylene while remaining lightweight and easy to work with. Lifespan is 5-10 years. Not the best insulator.

    5. Maintain Ideal Temperature and Ventilation

    The environment inside your greenhouse needs to be controlled to support healthy plant growth. Proper ventilation, air circulation, and temperature modulation are key.

    Adding Vents, Fans, and Shutters

    Ventilation is crucial in a greenhouse. Air vents provide a breath of fresh air and a cool breeze for stifling heat. Roof vents allow rising warm air to escape and are operated manually or automatically. Sidewall shutters bring in fresh outside air near the plant level. Small portable fans improve air circulation.

    Evaporative coolers are a good option for hot, dry climates. In humid areas, exhaust fans help reduce stickiness. Automated temperature-triggered vents provide climate control when you’re away.

    Controlling Humidity Levels

    Humidity directly affects plant transpiration and diseases. The optimal humidity level for most plants is around 60%. Dehumidifiers can lower moisture during humid weather. Fogging systems boost humidity in dry periods but increase potential disease issues.

    Season Day Temperature Night Temperature
    Spring 65-75°F (18-24°C) 55-65°F (13-18°C)
    Summer 75-85°F (24-29°C) 65-70°F (18-21°C)
    Fall 65-75°F (18-24°C) 50-60°F (10-16°C)
    Winter 55-65°F (13-18°C) 45-55°F (7-13°C)

    Opening vents regularly helps reduce condensation and control stuffiness. Air circulation from fans inhibits fungal growth and other moisture-related problems. Positioning heaters and intaking drier outside air can further manage humidity and temperature as needed.

    6. Customize Your Greenhouse Design

    While functionality is important, don’t neglect the design side of your greenhouse. Take time to consider how you will use the space. Include amenities like shelving, sinks, counters, and storage to create your ideal plant-growing environment.

    Adding Benches, Shelves, and Storage Solutions

    To maximize your greenhouse growing space, think in all directions. Use hanging baskets or upside-down grow bags for vertical production. Include wide shelves for starting seeds and moving plants. Sturdy benches allow easy access for caring for plants at waist height.

    For a compact footprint, incorporate tiered shelving on the walls. Install utility hooks, rods, and overhead racks for hanging tools. Optimize organization with bins, cabinets, and drawers for storage. A potting station or workbench also comes in handy.

    Incorporating Automatic Openers and Irrigation

    If you’re not home during the day, you may want to invest in an automatic ventilation system. These systems will turn on either by a timer or by sensing the humidity and heat in the greenhouse. Automatic openers control the operation of vents, windows, circulation fans, shade screens, and more to regulate the environment.

    Installing a watering system frees you from daily hand watering. Drip irrigation, misters, and foggers deliver efficient hydration. Connecting your system to a timer or electronic moisture sensor further reduces greenhouse maintenance.

    a product image of the Exaco Janssens Retro Royal Victorian VI (Three Sizes)

    Choosing Between a DIY Greenhouse or Greenhouse Kit

    You have two main options when it comes to obtaining a greenhouse: building from scratch using plans or purchasing a greenhouse kit for assembly. Weigh the pros and cons of each approach:

    Assembling a Greenhouse From Scratch

    Customization: A DIY greenhouse lets you create exactly the size and features you want. The possibilities are endless when building from the ground up.

    Cost savings: Sourcing your own materials may be cheaper than a pre-made kit, especially if you use salvaged windows and other repurposed building supplies.

    Challenging construction: Building a greenhouse from scratch requires significant DIY experience, time, and hard work. The lack of instructions can make the process frustrating.

    Benefits of Buying a Complete Greenhouse Kit

    Efficient assembly: Greenhouse kits include all the required parts and hardware along with step-by-step instructions for straightforward construction.

    Convenience: No need to design plans, shop for supplies, or cut lumber when using a kit. All the materials are delivered to your door ready to assemble.

    Potential cost savings: If you are buying a standard-size kit with no modifications to it, you may be able to find this at a lower price than what it would cost you to assemble all of the materials you will need.

    If you have great DIY skills, building from scratch may be rewarding. For an easier process, choose a quality greenhouse kit.

    a product image of the Hoklartherm Riga Greenhouses 3S

    Maximizing Your Greenhouse for Year-Round Growing

    One of the biggest advantages of a greenhouse is the ability to start growing earlier in spring and continue harvesting later into fall. With proper design choices, you can extend your greenhouse growing season into winter.

    Extending the Growing Season

    Here are tips for getting the most use from your greenhouse during cooler weather:

    • Install a heating system like a thermostatically controlled space heater to maintain above-freezing temperatures on cold nights.

    • Choose glazing materials like polycarbonate that provide good insulation.

    • Reduce heat loss by sealing any gaps and adding insulation.

    • Add grow lights to supplement natural light on gloomy winter days.

    • Shift to growing cool weather-tolerant crops like kale, chard, herbs, and root veggies in winter.

    • Start your summer garden early by growing heat-loving plants like tomatoes and peppers indoors.

    Winterizing Tips for Your Greenhouse

    To make the most of your greenhouse aim to design it much as you would a tiny house. Find creative ways to cram in as many plants and functions as possible while still creating a pleasing space to meet your emotional and psychological needs too. Here are some winterizing tips:

    • Ventilate on sunny winter days but seal up at night to retain warmth.

    • Add thermal mass like barrels of water to absorb and slowly release heat.

    • Insulate the Foundation Frame and edges of the greenhouse with rigid foam boards.

    • Keep plants off the cold floor by using benches, shelves, and hanging baskets.

    • Move outdoor container plants like citrus trees into the greenhouse for the winter.

    For a comprehensive guide on how to effectively winterize your greenhouse, check out our article on how to winterize a greenhouse.

    a product image of the interior of the Solexx Conservatory 16x20x96 - DELUXE

    Conclusion

    Building your own greenhouse gives you control over the design, cost, features, and functionality. Follow this guide to properly plan and construct a customized greenhouse suited to your gardening needs and climate. The satisfaction of growing your own plants in a hand-built greenhouse is well worth the effort.

    FAQs

    What type of plastic sheeting is best for a greenhouse?

    Polyethylene and polycarbonate sheets are common greenhouse plastic coverings. Polyethylene is inexpensive but less durable. Polycarbonate is more expensive but provides better insulation, durability, and light transmission. 4mm or triple-wall polycarbonate panels are ideal for home greenhouses.

    What is the best type of greenhouse for a beginner gardener to build?

    A freestanding greenhouse is the easiest type for a beginner to build. Lean-to and attached greenhouses require more advanced carpentry skills. Start with a small 6x8 freestanding greenhouse with a simple wooden or PVC frame that uses poly sheeting for glazing. DIY kits are also great for first-time builders.

    How can I keep my greenhouse warm in the winter months?  

    Insulate the north wall, add polycarbonate panels, seal any drafts, use thermal curtains, install a heater, and shift to growing cold hardy crops like kale and chard. You can also move container plants inside and utilize passive solar heating in cold months.

    Where can I learn how to build a greenhouse if I've never done it before?

    There are many resources for learning DIY greenhouse construction. Watch online video tutorials, read greenhouse building books and magazines, take a class at your local nursery, join a building forum to ask questions, and use step-by-step plans or kits for guidance during your first build.

    What type of greenhouse should I build if I want to build one perfect for growing vegetables and herbs?

    A gothic-arch-style greenhouse with a polycarbonate panel roof and walls is ideal for growing vegetables and herbs. The arched roof provides plenty of overhead space and sunlight exposure. Install raised beds on the gravel or concrete floor for ease of access.

    What are some greenhouse ideas for utilizing the back of my property while building on a budget? 

    Consider a lean-to greenhouse attached to a back fence or wall to save space and materials. Use PVC pipe or repurposed windows for the frame, and cover with poly film plastic sheeting. Add a screened door to help control temperature and pests. Decorate the back wall with paint or murals. Use shelves and vertical hanging racks to maximize space.

    Previous article Building vs Purchasing a Greenhouse: An In-Depth Comparison
    Next article What Direction Should a Greenhouse Face for Optimal Plant Growth?

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    About The Author

    Andy Wu - Resident Expert

    Andy Wu - Resident Expert

    Andy Wu is the resident backyard products expert and hails from Atlanta, Georgia. His passion for crafting outdoor retreats began in 2003.

    As a fellow homeowner, he founded Backyard Oasis to provide top-quality furnishings and equipment, collaborating with leading manufacturers.

    His main focus is on sheds and generators!

    In his spare time he like to hike the tallest mountains in the world and travel with his family.

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