Components of a DIY Greenhouse
Whether your DIY greenhouse is going to be a simple poly-tunnel or a Victorian glass palace, the basic components are going to be the same: the foundation, the flooring, the frame and the covering material. Everything else, like doors, windows, benches, drainage system, environmental control (fans, heaters, misters, sprinklers etc.), can come later.
Small home greenhouses can be built over bare ground, and part of the foundation can be even used for direct planting, but most people prefer to make a solid foundation, which usually means a concrete floor. Concrete floors are clean, drain well (if well poured), and will keep a greenhouse free of pests, weeds and fungus. Light-colored concrete floors also reflect light. Another important advantage of a concrete foundation is that it provides good base for any type of the greenhouse frame.
A cheaper, but also good, solution for the foundation is a plastic barrier over well-leveled ground consisting of three to four inches of gravel or crushed rock. Gravel and rock are easy to install, drain very well, and retain moisture, which evaporates during the day, adding to the cooling effect inside your greenhouse. With this type of foundation, you will have to install a base frame to which you will attach the wall frames for the greenhouse. It usually means digging a ditch around the perimeter, filling it with a layer of gravel for drainage, and placing a solid wood base frame on top of the gravel.
Your major consideration when choosing a frame for your greenhouse, besides the cost, is your location. If you have heavy snows, the frame has to be able to support heavy loads. If the strong winds are a problem, you need a heavier, more solid frame. If the climate is humid, you should stay away from more sensitive wood. The load-bearing capacity is mostly determined by the space between roof beams or hoops. The closer they are, the stronger the frame will be.
Stainless or galvanized steel framing is by far the strongest and the longest lasting framing, but also the most expensive.
Aluminum is durable and resistant to weather and will not rust. Most greenhouse kits have aluminum framing. Aluminum is strong, but fairly costly.
Wood makes very attractive greenhouse frame, but it requires regular maintenance. Wood is sensitive to humidity, and it has to be treated yearly, to prevent it from rotting. It is an excellent choice in a dry climate.
Plastic (PVC) greenhouse frames are cheap and easy to install, but light and not suitable for heavy winds. Plastic also deteriorates in time even if it is UV-resistant.
Glazing or covering is what makes the greenhouse what it is. It is supposed to permit the light and sun inside, to conserve and retain heat and prevent the cold from entering the greenhouse. The right choice of the greenhouse covering is what will make or break your greenhouse.
Glass has been used in greenhouse construction for centuries for its beauty and heat retention, especially if double or triple glazed. Glass is fairly expensive and fragile and does not defuse the sun very well, so it requires shading to prevent plants from burning. It also needs a very solid frame to sit upon because of its weight.
Fiberglass is very similar to glass, with the advantage of being less fragile, was the first practical substitute for glass. It is much lighter than glass and is translucent, what means it diffuses light. It does not last as long as glass and in time it becomes less clear and allows less light for plants.
Polycarbonate is a relatively new material, which offers many advantages for greenhouse glazing. It is strong, offers great insulation; it diffuses light and is fire-resistant. It is also one of the longest lasting glazing materials – up to 15 years.
Polyethylene is the most commonly used greenhouse glazing material. More than 90 percent of people chose poly film for their greenhouses because of affordable price, ease of installation, lightweight, have excellent light transmission and retain heat very well. The only downside to poly film is its short life – about two years. The best kind of polyethylene glazing has two layers, with a layer of air between, for increased heat retention.
Greenhouse Vents and Windows
Greenhouse vents, shutters and windows all serve the same purpose: to allow fresh air in and hot air out, helping to keep the temperatures moderate, and providing air circulation for the plants. Vents can be simple greenhouse panels that are opened when needed. Windows do the same job. Vents and shutters can also be automated, so that you do not have to be around every time when the vent has to be opened or closed. Some vents are solar-powered and do not require electricity. Fans installed in front of vents increase the circulation of the air in the greenhouse and ensure that the heat is evenly distributed.
Greenhouse Benches and Shelves
Benches and shelves not only keep your plants off the ground and away from bugs, fungus and bacteria, but they help organize your greenhouse and allow for more space for growing beds, pots, trays, tools and materials. They can be made of metal, plastic or wood, can be single-level or multi-level, fixed or on casters, but they all have to allow free drainage of water and easy cleaning and maintenance.
The Rest of It
You might start with just a foundation, frame and glazing, but very soon you will want more: misting systems, a watering system, fertilizing system, heating system, you will want to automate everything so that you would be free from boring chores and have the time to enjoy the fruits of your labor. But, to start with, you can do without all those time saving tools. Start with just a few plants and let your DIY greenhouse grow naturally.