How to Build a Small Greenhouse from PVC: A DIY Guide - Plant Care Guide

Creating a controlled environment for your plants can extend your gardening season, protect delicate seedlings, and even allow you to grow a wider variety of crops. Learning how to build a small greenhouse from PVC offers a cost-effective, relatively simple, and customizable solution for any home gardener looking to expand their growing capabilities without a hefty investment.

Why Build a PVC Greenhouse?

Opting to build a small greenhouse from PVC offers numerous practical advantages, especially for the home gardener. It's a fantastic entry point into greenhouse gardening without the significant financial or time commitment of a traditional structure.

Here are the compelling reasons why a DIY PVC greenhouse is a smart choice:

• Cost-Effective: PVC pipes are relatively inexpensive, making this one of the most budget-friendly ways to get a greenhouse. You can often build a functional structure for a fraction of the cost of pre-fabricated kits.
• Easy to Build: PVC is lightweight and easy to cut, assemble, and work with. Most projects require only basic tools and can be completed by a single person or with minimal help.
• Customizable Size: You can tailor the dimensions of your greenhouse to fit your specific space and growing needs. Whether you need a small cold frame or a walk-in structure, PVC offers flexibility.
• Portability/Temporariness: Unlike permanent structures, a PVC greenhouse can often be disassembled and moved if needed, or used as a temporary season extender. This is ideal for renters or those who want flexibility.
• Lightweight: The frame is light, making it easy to shift or adjust if necessary.
• Rust-Resistant: PVC does not rust, which is a major advantage over metal frames, especially in humid greenhouse environments.
• Extend Growing Season: Protects plants from early frosts and extends the harvesting period into cooler months.
• Seed Starting: Provides an ideal warm, humid environment for germinating seeds and hardening off seedlings before transplanting them outdoors.
• Protection: Shields plants from harsh winds, heavy rains, excessive sun (with shading), and some pests.

What Materials and Tools Do You Need?

Before you begin to build a small greenhouse from PVC, it's crucial to gather all your materials and tools. Having everything ready will make the construction process much smoother and more efficient.

Materials:

1. PVC Pipe:
   • Schedule 40 PVC Pipe: This is the standard, rigid white pipe. For small greenhouses, 1/2-inch to 1-inch diameter PVC is generally sufficient. 1/2-inch is good for very small, low structures, while 3/4-inch or 1-inch provides more rigidity for taller, wider greenhouses. You'll need several long sections, typically 10-foot lengths.
   • Quantity: Depends on your greenhouse design. It's always wise to buy a little extra for mistakes or future modifications.
2. PVC Fittings: These connect the pipes to form the frame.
   • Elbows (90-degree): For corners.
   • Tees: For joining three pipes, often for horizontal supports.
   • Crosses (4-way tees): For joining four pipes at an intersection (less common but useful for complex designs).
   • End Caps: To cap off open pipe ends for a cleaner look and to prevent dirt/pests.
   • 3-way, 4-way, or 5-way Corner Fittings: Specific PVC fittings designed for structural corners, making assembly easier and stronger than multiple standard fittings. These are often labeled "furniture grade" PVC fittings.
   • Couplings: For connecting two straight pieces of pipe.
3. Greenhouse Plastic Sheeting (Covering):
   • UV-Resistant Polyethylene Film: This is the standard for greenhouses. Look for at least 6-mil thick, UV-treated film. It's designed to resist degradation from sunlight and often includes anti-drip features. Purchase a size that will fully cover your frame with extra for overlapping. Greenhouse plastic film is essential.
4. Fasteners for Plastic:
   • Spring Clamps or Snap Clamps: These are the easiest way to attach the plastic to the PVC frame. Heavy-duty spring clamps (like those used for woodworking) work well.
   • Duct Tape or Greenhouse Repair Tape: For securing edges or making minor repairs. UV-resistant greenhouse repair tape is best.
   • Zip Ties: For extra security in some areas.
5. Anchoring Materials (for outdoor use):
   • Rebar or Ground Stakes: To anchor the PVC frame to the ground and prevent it from blowing away. You'll need pieces of rebar slightly smaller than your PVC diameter (e.g., 1/2-inch rebar for 3/4-inch PVC) cut to about 18-24 inches long.
   • Concrete Mix (Optional): For a more permanent base, PVC can be set into small concrete footings.
6. Base Materials (Optional):
   • Treated Lumber or Railroad Ties: For a sturdy, level base for your greenhouse frame to sit on. This can also prevent the PVC from sinking into soft ground.
   • Gravel: For drainage inside the greenhouse.

Tools:

1. PVC Pipe Cutter: This specialized tool makes clean, straight cuts through PVC quickly and easily. A ratcheting PVC cutter is highly recommended.
2. Tape Measure: For accurate measurements of pipe lengths.
3. Marker: To mark cut lines on the PVC.
4. Drill and Drill Bits: For drilling pilot holes if using screws for reinforcement (less common with PVC cement, but good for custom attachments).
5. Rubber Mallet (Optional): For gently tapping fittings together if they are very tight.
6. Shovel or Post-Hole Digger (for outdoor anchoring): To prepare holes for rebar or base.
7. Level: To ensure your base is even.
8. Safety Glasses and Gloves: Always protect your eyes and hands when cutting and working with tools.

Designing Your Small PVC Greenhouse

Before you cut a single pipe, planning and designing your PVC greenhouse is crucial. A good design ensures stability, functionality, and optimal growing conditions.

Consider Your Space:

• Available Footprint: How much space do you have in your yard, patio, or balcony? Measure the length and width precisely.
• Height Restrictions: Are there any overhead obstructions (trees, eaves)?
• Sunlight: Observe where your chosen spot gets the most sunlight throughout the day and across seasons. Ideally, your greenhouse should receive at least 6 hours of direct sun daily. Orient the longest side towards the south for maximum light exposure.

Determine Your Needs:

• What will you grow?
  • Seed Starting: A shorter, bench-height greenhouse might suffice.
  • Tall Plants (Tomatoes, Peppers): You'll need adequate height, especially in the center.
  • Overwintering Plants: Consider size and insulation needs.
• Walk-in vs. Cold Frame: Do you need to stand inside or just access from the top/side?
• Ventilation: How will you manage heat buildup? A roll-up side, a door, or vents are necessary.
• Door Access: Will it have a full door, or will you lift a side?

Sketch Your Design:

Draw a simple diagram, including dimensions (length, width, height). This will help you calculate the amount of PVC pipe and fittings you'll need.

Common PVC Greenhouse Designs:

1. Hoop House/Quonset Style:

   • Description: The most common DIY PVC greenhouse. Arched hoops form the roof, offering good wind resistance and shedding snow.
   • Frame: Usually, a rectangular base with PVC arches bent over it.
   • Pros: Good for shedding snow and wind. Relatively easy to build.
   • Cons: Less vertical side wall space, so plants can't be pushed right to the edges.
   • Good for: General purpose, seed starting, growing row crops.

2. A-Frame/Gable Roof Style:

   • Description: Resembles a traditional house roof, with angled sides meeting at a ridge.
   • Frame: More complex, involving multiple triangular sections.
   • Pros: More vertical side walls, allowing plants closer to the edge. Good drainage.
   • Cons: More cuts and fittings required. Can be more challenging for beginners.
   • Good for: Walk-in structures, where maximum interior space is desired.

3. Cold Frame (Mini Greenhouse):

   • Description: A small, low structure, usually less than 3 feet high, with a lid that opens.
   • Frame: Simple rectangular box, often just a few pipes and corner fittings.
   • Pros: Very easy to build, uses minimal materials. Ideal for seed starting and hardening off.
   • Cons: Limited space, not walk-in.
   • Good for: Protecting small plants, extending season in a limited space.

Calculate Materials:

Once you have your design and dimensions, calculate the total linear feet of PVC pipe needed for all horizontal, vertical, and arched sections. Then count all the necessary fittings (elbows, tees, corners, etc.). Add 10-15% extra for errors or future adjustments.

Step-by-Step Construction: Building Your PVC Greenhouse

This guide focuses on a popular and relatively simple hoop house design, often the best type of small greenhouse from PVC for beginners.

Phase 1: Building the Base Frame

The base provides the foundation and anchors for your PVC greenhouse.

1. Choose Your Site: Select a level, sunny spot for your greenhouse.
2. Prepare the Ground (Optional but Recommended): For better stability and drainage, you can lay down a perimeter of treated lumber (4x4s or 2x6s) to create a rectangular base for your PVC frame. Level it carefully.
3. Cut Base PVC Pipes: Based on your design sketch, cut four pieces of PVC pipe for the length and width of your base.
   • Example: For a 6 ft x 8 ft greenhouse, you'd cut two 6-foot pipes and two 8-foot pipes.
4. Assemble Base: Connect the four base pieces using four 90-degree PVC elbows to form a rectangle. Dry-fit first to ensure everything aligns. You can use PVC cement for a permanent connection, but for a temporary structure, dry-fitting allows disassembly.
5. Anchor the Base (Outdoor Use):
   • Drive rebar stakes (approx. 18-24 inches long) into the ground along the inside perimeter of your base frame, spaced about 2-3 feet apart. Leave about 6-12 inches of rebar sticking out of the ground.
   • Slide the assembled PVC base frame down onto the rebar stakes, ensuring the rebar fits snugly inside the PVC pipe. This will prevent your greenhouse from blowing away in the wind.

Phase 2: Creating the Hoops (Arches)

The hoops form the main structure of your greenhouse's roof.

1. Determine Hoop Length: The length of your PVC pipes for the hoops will determine the height and width of your greenhouse.
   • General Rule: For a typical 6-foot wide greenhouse, a 10-foot long PVC pipe will create a hoop approximately 6 feet high at its peak. Longer pipes will create wider or taller hoops. You can test bend a piece to find your desired curve.
2. Cut Hoops: Cut multiple identical pieces of PVC pipe for your hoops. The number of hoops depends on the length of your greenhouse (e.g., for an 8-foot long greenhouse, you might need 5 hoops, spaced 2 feet apart, one at each end).
3. Install Hoops:
   • Slide each cut hoop pipe onto the protruding rebar stakes on opposite sides of the base frame. The PVC should bend naturally into an arch.
   • Repeat for all hoops, ensuring they are evenly spaced along the length of your base.
   • If you don't use rebar, you can attach the hoops directly to the base frame using specific PVC cross-fittings designed for this purpose, which can be more complex to source and assemble.

Phase 3: Adding Ridge Poles and Supports

Ridge poles add rigidity and connect the hoops, making the structure strong.

1. Cut Ridge Poles: Cut long pieces of PVC pipe to span the length of your greenhouse, connecting the tops of the hoops. You'll typically need at least one central ridge pole. For wider greenhouses, you might add two more parallel ridge poles halfway between the center and the sides.
2. Connect Ridge Poles: Use PVC tees or special snap-on ridge pole clamps to connect the ridge poles to the top of each hoop.
3. Add Side Supports (Optional but Recommended): For increased stability and to provide attachment points for shelves or equipment, you can add horizontal support pipes along the sides of the greenhouse. Connect these using tees or 4-way fittings.

Phase 4: Constructing the Door Frame (Optional)

If you want a walk-in greenhouse, a door frame is essential.

1. Design Doorway: Decide on the size and location of your door. Typically, one end of the hoop house is chosen.
2. Cut Door Frame Pipes: Cut vertical and horizontal PVC pieces to form a rectangular door opening within one of the end hoops.
3. Assemble Door Frame: Use 90-degree elbows and tees to create the door frame. Attach it to the existing hoop structure. You can add a vertical support from the center of the base to the top of the door frame for added stability.
4. Create Door Panel: Cut a separate piece of PVC and plastic for the actual door. This can be a simple rectangle that pivots on hinges (made from extra PVC, or actual PVC hinges) or a roll-up flap.

Phase 5: Applying the Greenhouse Plastic Covering

This is where your PVC frame truly becomes a greenhouse.

1. Choose a Calm Day: Pick a day with minimal wind to apply the plastic.
2. Drape Plastic: Drape the greenhouse plastic film over your entire PVC frame. Ensure there's plenty of overhang on all sides.
3. Secure One Side: Starting on one long side, pull the plastic taut and secure it to the base PVC pipe using spring clamps or by burying the edge in the soil.
4. Pull Taut and Secure: Go to the opposite long side, pull the plastic very taut to remove wrinkles, and secure it. Repeat this process for the ends, pulling tightly around the curves of the hoops.
5. Seal Edges: Use greenhouse repair tape or duct tape to create a strong seal around all edges, especially at the base and around any door openings. This minimizes drafts and heat loss.
6. Form the Door: If you have a door frame, cut the plastic to fit the opening, leaving enough excess to create a flap that can be secured with clamps, zippers, or Velcro for easy access.

Phase 6: Final Touches and Reinforcement

• Reinforce with Zip Ties: For added security, especially in windy areas, use UV-resistant zip ties to fasten the plastic to the PVC frame at critical points.
• Dig a Trench (Optional): For better insulation and wind resistance, dig a shallow trench around the base of the greenhouse and bury the excess plastic film.
• Add Vents: Cut openings for vents (can be simple flaps secured with clamps) or create a roll-up side for ventilation. Good airflow is essential to prevent overheating and fungal diseases.

Optimizing Your PVC Greenhouse for Growth

Building the structure is just the first step. To ensure your plants thrive in your new PVC greenhouse, you need to manage its internal environment effectively.

Ventilation is Key

One of the most critical aspects of greenhouse management is ventilation. Without it, temperatures can soar on sunny days, cooking your plants, and stagnant air can encourage fungal diseases.

• Roll-Up Sides/Ends: Design one or both long sides, or the ends, to be roll-up. This is often done by securing the bottom edge of the plastic to a pipe, which can then be rolled up and secured with clips or ties.
• Vents/Windows: Cut openings high up on the greenhouse walls or ends. These can be simple flaps secured with clamps, or you can add screened windows to keep pests out.
• Fans: For larger PVC greenhouses, a small solar-powered fan or an oscillating fan can significantly improve air circulation.

Temperature Management

Controlling the internal temperature is vital for plant health.

• Thermometer: Place a minimum/maximum thermometer inside the greenhouse to monitor temperature swings.
• Shade Cloth: In hot climates or during peak summer, temperatures inside can become excessive. Drape shade cloth over the greenhouse to reduce direct sunlight and lower internal temperatures.
• Heating (Optional): For overwintering or extending the season in very cold climates, a small electric heater for greenhouses with a thermostat or even simple heat sinks (like dark water barrels) can provide warmth.

Humidity Control

High humidity can encourage fungal issues.

• Ventilation: Again, good airflow is the best way to manage humidity.
• Watering: Water plants in the morning so excess moisture can evaporate throughout the day. Avoid overhead watering late in the day.

Internal Setup

• Shelving: Add simple PVC shelving or wire shelves to maximize growing space vertically.
• Raised Benches: Build small raised benches inside for easier access to plants and improved air circulation around pots.
• Water Source: Consider a nearby water source or a rain barrel to make watering convenient.

Troubleshooting Common PVC Greenhouse Issues

Even with the best small greenhouse from PVC, you might encounter some common challenges. Knowing how to address them ensures your plants remain healthy and your structure lasts.

Problem: Greenhouse Blows Away in Wind

• Cause: Insufficient anchoring.
• Solution: Reinforce anchoring! Drive rebar deeper, add more stakes, or secure the base to heavy timbers. For severe winds, consider adding external guy ropes anchored to the ground. Burying the plastic edges in a trench also helps.

Problem: Plastic Tears or Degrades Quickly

• Cause: Using non-UV treated plastic, insufficient thickness, or poor installation (too much tension in one spot, sharp edges).
• Solution: Always use 6-mil UV-treated greenhouse plastic. Ensure there are no sharp edges on your PVC frame that could abrade the plastic. Use greenhouse repair tape immediately for any small tears to prevent them from growing.

Problem: Plants Overheating

• Cause: Insufficient ventilation, too much direct sun.
• Solution: Increase ventilation by opening doors/vents wider. Add more vents if needed. Consider adding shade cloth during the hottest parts of the day or season.

Problem: High Humidity/Fungal Diseases

• Cause: Poor air circulation, overwatering, too much moisture on plant leaves.
• Solution: Maximize ventilation. Water plants in the morning to allow foliage to dry during the day. Consider a small fan to move air. Ensure adequate spacing between plants.

Problem: Structure Sags or Collapses Under Snow Load

• Cause: Insufficient pipe diameter, lack of enough hoops/supports.
• Solution: For areas with heavy snow, use larger diameter PVC (1-inch or more) and add more hoops and horizontal supports. If snow is expected, actively clear it from the roof. This type of greenhouse is not designed for heavy, prolonged snow loads without intervention.

Problem: Poor Plant Growth

• Cause: Too little light (if greenhouse is in a shady spot), improper watering, nutrient deficiencies.
• Solution: Ensure the greenhouse location gets at least 6 hours of direct sun. Monitor watering. If plants are mature and show signs of nutrient deficiency, a balanced plant fertilizer may be needed.

Building a small greenhouse from PVC is a rewarding project that empowers you to take greater control over your gardening environment, allowing you to grow a wider array of plants, extend your growing season, and enjoy fresh produce or beautiful blooms year-round.