Build a Backyard Greenhouse

If you're disappointed with the results of short growing seasons or a climate that limits your plant selection a backyard greenhouse is the solution. This structure will provide a controlled environment where -- depending on the environment you create -- exotic fruit, orchids, vegetables, herbs and flowers can thrive year round.

Types of greenhouses

Green houses are either free standing or a lean-to style that is attached to one side of the house or another building. A low-walled box with a covered, lift-up frame will work even in small yards. In areas where the earth can be dug easy, a sunpit is another option. Sunpit greenhouses are partly in the ground and this takes advantage of the earth’s insulation for cooling and heating, though they have the same ventilation and the other requirements as greenhouses. The plants you want to grow will serve as a guildline for which type of greenhouse to build. Vegetables for instance, need a large amount of light and space. Starting with a size somewhat bigger than what you think you'll need will give you room to expand. Also, for walk-in greenhouses, check with local authorities about building permits or other restrictions before you start work.

Material

A greenhouse consists of flooring, wall frames, walls, and roof material. A simple lean-to design with an earth floor and gravel path, cedar frame, and Fiberglass covering -- as well as any heating or cooling equipment -- should provide a suitable environment for most plants.

Location

Locate your greenhouse where there will be enough room and sunlight for the types of plants inside. Consider which direction light enters your property from and how intense that light is -- for example, if a large tree is blocking southern light, the west may be getting more light. In moderate climates in the northern hemisphere, the best location is south side of the house. During early spring and late autumn, this is where you will get the maximum exposure to available sunlight. This way a lean-to greenhouse will take advantage of the warm wall of your home. A location near the house will also make it easier to run water and electricity to greenhouse.

How to build a greenhouse: basic guidelines

An effective greenhouse doesn't have to be expensive -- a simple structure can be designed from scrap material. As to construction, the lean-to design is the easiest to build. Here are some guidelines from the ground up.

Foundation and flooring

The flooring for your greenhouse can be concrete or bare earth with a path of gravel, or brick, or flagstone down the middle to save you from walking in the mud. Many put in decorative brick or rock that is laid in sand. Whatever you choose, it should be porous to avoid pooling water and mud.

Frame

How you construct the framing will vary depending on the type of greenhouse you plan to build, but the material is essentially the same. Cedar or spruce two inch by two inch or two inch by four inch beams are cost-effective and sturdy enough to last. Square lumber, rather than rounded building logs, will make the construction simpler. Avoid railroad ties, which can leach toxic chemicals into the soil and water. For a greenhouse with low (two-foot-high or lower) walls, a frame with Fiberglass, plastic or glass covering can be attacted to the low main walls. Larger greenhouses may have the covering extend down to the foundation.

Covering

Fiberglass or other rigid plastic, either flat form or corrugated form, retains heat better and than glass or plastic film, is more durable that plastic film, and can be attached to a straight surface or a curved one. In warm climates, a fiberglass greenhouse requires less cooling and insulation and UV-resistant panels are also available. Fiberglass panels can be installed using large-headed roofing nails. Plastic sheeting, while effective, will fall apart quickly, but it's a low-cost solution for a temporary greenhouse. Plastic can be installed with a staple gun, stapling it down tightly and evenly to prevent the wind from lifting it and tearing it apart. Glass works well, but it's the most expensive and if damaged can be almost impossible to clean up.

Heating and cooling systems

Cooling, heating, and ventilation needs depend on climate and types of plants grown. Consider the individual requirements of each plant and locate it in the part of the greenhouse that will best meet its needs.

Heating a greenhouse

Cold climates require well-insulated greenhouses. A solar greenhouse will, as the name implies, absorb more light than the other types, which will save on the heating bill. Heat can be stored in any material that absorbs heat well, such as barrels or jugs of water or a brick or rock wall. Solar systems may be passive (which does not use a mechanical device to distribute solar heat from a collector) or active (which uses collectors to absorb solar radiation and electric fans or pumps to distribute the heat through the air).

Cooling a greenhouse

In very hot climates, the greenhouse will need cooling. Shade cloths are the simplest method of cooling, with swamp or evaporative coolers next in line. A swamp cooler is a large frame holding a fan walled in by pads of wood (usually aspen) fiber. These pads are kept wet by a water pump. As the fan draws hot air past them, the water evaporates and cools the air. This work well only in dry desert areas, but not in areas with high humidity.

Ventillation

Because a greenhouse is so well enclosed, ventillation is a special consideration. A door that can be propped open, or hatches or windows in the roof or walls are usually enough. For greenhouses with a larger crowd of plants, a fan can be installed.

Safety

In climates with frost, any water lines must be covered to prevent them from freezing and breaking. All electrical outlets must be water resistant and ground fault circuit interrupters should be used also. Keeping tools, as well as the entire greenhouse, clean will minimize plant disease.

Equipment

Many everyday chores can be automated, which not only saves time, but ensures precision. A ventillation fan, misting system, automatic watering system, and heating system -- depending on your needs -- can all help. Be sure that the accessories you choose are they appropriate size for the greenhouse. High quality equipment, although it may require a higher initial investment, will save money on repair and replacement costs in the long run.

Potting benches and tables will give you enough space to do your planting right. Tool racks -- even a simple board with nails -- helps keeps tools clean and ensures the tool you need is there when you need it. Hooks for hanging baskets can be added for more space to keep plants. A cabinet for potting soil, fertilizers, and other material will help keep things organized and prevent spills.