How to Build a Greenhouse

Choose a site with good drainage and good sun exposure throughout the day. Position the greenhouse so it will face south and an open sky. This will maximize sun exposure during the cold months. The site should also be level or close to level.

Most gardeners also choose a site close to a source of electricity and water.

Not all greenhouses are built on foundations, but you may want one if your ground is not stable. Take into consideration how you’ll attach it to the greenhouse frame.

• When building your own greenhouse, start by leveling the site. Cold climate gardeners should put their foundations below the frost line and insulate them, if desired.
• Material choices for a foundation include ground contact-rated wood and poured concrete.

Whether you pour concrete or build a wooden foundation, use a tape measure and make the foundation slightly larger than the base of the greenhouse will be when it's finished.

• If you don’t use a foundation, use landscape fabric, bricks, gravel or another material that drains easily for the greenhouse floor.

Lumber, PVC pipes, aluminum and galvanized steel are often used to make greenhouse frames.

• Wooden greenhouses are beautiful, but high humidity and dampness can cause rotting. Use a moisture and rot-resistant timber such as cedar and a ground contact-rated wood for the foundation.
• PVC pipes are easy to use, inexpensive and lightweight. They're good to use for small backyard greenhouses. Most PVC greenhouses are covered with polyethylene sheeting. Choose UV-resistant PVC pipes to make the frame last longer.
• Aluminum doesn’t rust and makes a good frame for glass or polycarbonate panels. For a strong, sturdy greenhouse, use heavy gauge aluminum.
• Galvanized steel will rust, so it’s not a common choice for a backyard greenhouse. However, commercial growers often use galvanized frames and polyethylene greenhouse coverings.

Choose a covering for your DIY greenhouse that can withstand weather extremes. Different materials allow different amounts of light to enter. Greenhouse covering choices include:

• Greenhouse glass panels: These can break if they’re hit by hail or a stray object. However, if the glass is tempered, it will shatter into small pieces that are less dangerous than standard glass that breaks into sharp shards. Greenhouse glass panels are also beautiful and sturdier than plastic sheeting or polycarbonate sheets. Glass panels allow plenty of light to enter. They may be more expensive upfront, but they can last for many years. Double pane glass is a better insulator than single pane glass.
• UV-resistant polycarbonate sheets: Made from a thick plastic, UV-resistant polycarbonate is durable and less expensive than glass. It’s not as heavy as glass, yet it retains more heat and provides better insulation. Polycarbonate plastic for a greenhouse can become yellow or cloudy over time, which reduces the amount of light transmitted, so expect to replace it. Most UV-resistant polycarbonate is warranted for five to ten years. Some manufacturers' warranties go up to 15 years.
• Plastic sheeting: Also called polyethylene sheeting, greenhouse plastic sheeting is lightweight and inexpensive. It’s less durable than polycarbonate sheets, however. The sheets usually need to be replaced once year. Use double layers of the best greenhouse plastic you can afford for better insulation. Be aware that more layers reduce the amount of light plants get.

Glass greenhouses are the most popular types of greenhouses. Use a building plan or create your own. Practice safety when working with glass. Wear eye protection and use cut-resistant gloves.

• It’s usually best to build wall frames for a glass greenhouse on the ground or other flat surface and then raise them into place.
• For a relatively simple greenhouse, build an A-frame roof with rafters.
• You may need to cut your greenhouse glass or have it cut to fit. For safety, use tempered or safety glass that will not break into jagged pieces. Do not use glass made to filter out sunlight.
• Install the glass panels after the frame is up.

• You'll need lumber, hardware and covering materials for a greenhouse made out of wood. Rental trucks are available to help you transport your tools and supplies.
• Consider your climate before you choose the materials for your greenhouse. Wood is a good choice for a warm, dry climate.
• Wood greenhouses can be designed to complement the style of your home.
• Wood is durable, a good insulator and long-lasting, especially if it's pressure treated or otherwise treated for outdoor use. If you use treated wood, be sure it is completely dry before using it.
  Use ground contact-rated wood for a foundation.
• Wood can be cut with a miter saw, and pieces can be joined with screws, nails or other types of fasteners.

PVC pipe is easy to cut, lightweight and inexpensive. Sunlight may eventually discolor PVC, but in general, it makes a long-lasting and durable frame.
Keep in mind that greenhouse kits are a convenient, all-in-one solution.

• Cut PVC pipes to the size you've chosen and connect them with PVC glue for a permanent bond. Follow the manufacturer’s direction when using PVC glue or cement and work outside or in a well-ventilated area.
• If you plan to move the greenhouse, use temporary connectors such as bolts or screws, or drill holes in the pipes and zip-tie them together so you can reassemble it later. If the greenhouse is small enough, you may be able to move it in one piece.
• Use PVC fittings like elbows, tees and wyes to join PVC pipes at various angles.
• PVC pipes can be gently bent to form arches and other shapes.
• After you learn how to build a PVC greenhouse, consider using lightweight plastic sheeting to cover it. Tuck the sheeting around the PVC and secure it to eliminate any gaps.

This is an overview of building a greenhouse from windows. Ask a building associate with The Home Depot for advice if you need help.

• Use old or recycled tempered or safety glass windows if possible. Standard glass can break into dangerous shards.
• Build a foundation for a greenhouse made of old windows, since it will probably be heavy.
• Start with old windows of about the same size. Put them on the ground and arrange them into four sections for the walls. Leave an opening for a door and for a fan, if desired.
• Have a friend help you raise the sections onto the foundation.
• Seal any gaps and cracks and paint the wood or use a sealant.
• Use a lightweight, waterproof material for the roof. Slant the roof so rain and snow don’t accumulate.

A small DIY greenhouse is perfect for growing a few plants. It's handy to have in early spring when you're ready to start seeds. You can purchase a mini greenhouse or build one following these guidelines:

• Start by using six old windows of the same size.
• Build a wooden frame to hold the windows.
• Build an A-frame to support the roof and attach it to the frame.
• Screw five of the windows onto the wooden frame.
• Attach the last window with a hinge on one side, so you can open it and reach inside.

It's also easy to make a mini-greenhouse from PVC. Simply cut PVC pipes to the sizes you want and join them with PVC fittings. Cover the greenhouse with plastic sheeting.

Greenhouse supplies and accessories, if you have room for them, can make your greenhouse more useful and enjoyable.

• Use roof vents or open a door or flap to prevent overheating from the sun. Electric and automated, temperature-sensitive ventilation systems are available.
• Use a fan to circulate air.
• Add a dehumidifier if humidity becomes a problem and opening doors and vents doesn't help.
• Add greenhouse shelves, benches or tables to hold plants and potting supplies.
• Install hooks to hold tools.

When you build with a greenhouse kit,all of the pieces are conveniently provided for you. For this project, we used the Palram Snap & Grow Greenhouse Kit, but there are many kits available for other types and sizes of greenhouses, including those made of metal, wood and resin. Assembly instructions will vary by kit, so follow the manufacturer’s instructions on how to build a greenhouse. Basic steps are listed below. Detailed instructions are included with the kit.

• Take inventory before beginning. Unpack the kit and make sure you have all the pieces listed in the manufacturer’s instructions. In addition to the listed tools and materials, you will also need scissors and cleaning cloths.
• Assemble the base and corner uprights.
• Attach the roof frame.
• Install wall uprights and roof rafters. You must assemble the frame in the order specified by the manufacturer to keep the structure stable during the building process.
• Install wall panels
• Optional: Install ventilation windows.
• Install doors.
• Install supports.
• Customize your greenhouse with shelves, benches, tables, hooks or other accessories.