How to Build a Backyard Greenhouse
Michael Franco | Zillow Blog | September 16, 2013 | link
Source: Groundswell Design Group, LLC
Shorter days, colder temperatures and frozen earth: For most, the advent of winter marks the year’s end of planting, pruning and picking. Greenhouses — backyard structures of varying sophistication — extend the growing season well beyond the sun of spring and summer, providing a soul-warming haven of green for their cultivators. In fact, a well-maintained greenhouse can supply fresh vegetables for the dinner table, even in the midst of a snowstorm.
It doesn’t really matter where you put the birdbath, but choosing an appropriate site for a greenhouse is critically important. The ideal location is the south side of your property, where the greenhouse is most likely to receive the most sunlight throughout the seasons. A west-facing site is a good second option.
No matter the location you ultimately choose, take pains to ensure the greenhouse is going to get good morning sun. Observe the way light falls over your yard throughout the day, and plan around any trees or outbuildings that cast shadows on your property. Don’t avoid foliage entirely, as deciduous trees provide valuable shade that protects a greenhouse from the strong midday summer sun. And when the leaves drop in winter, the greenhouse welcomes the scant winter light.
While sun exposure takes priority, it’s also important to protect your greenhouse from the elements. Areas rimmed by a fence or a line of shrubbery are preferable, as those barriers tend to diminish the strength of winds that otherwise would steal vital heat from the interior of your grow zone.
Source: Cross Country Greenhouses
Design & layout
In the case of greenhouses, size matters. If you’ve never had a greenhouse before, you might be tempted to build a small one. Counterintuitively, small greenhouses are the most challenging, even for experienced growers, because they are prone to dramatic temperature fluctuations.
Meanwhile, a larger greenhouse requires commensurately more powerful heating and cooling equipment, making the initial and ongoing costs mount. The recommended minimum dimensions are 6 feet wide by 12 feet long. A 17-foot-wide design offers an appealing ratio between the size of the structure and the amount of usable area inside.
A favorite layout involves three long tables — often called “benches” — with one running down the middle and one along each side, leaving a walkway between. For maximum flexibility, consider adding caster wheels to a collection of several benches so you can reconfigure the greenhouse as the light fluctuates from season to season.
Buy or create benches topped with a durable waterproof material, as much for easy cleanup as longevity (laminate countertops are a popular choice). As a safeguard against rust, opt for plastic or fiberglass storage shelving.
As you plan the construction of your greenhouse, two central questions must be answered: In what shape will it be built, and what materials will be used?
Shape. The right shape for your greenhouse depends on your climate. If you live somewhere that frequently gets snow, a pitched roof is a must. Elsewhere, a rounded roof structure may be used (options include Quonset or Gothic styles). If you’re tall, however, be aware that it may be difficult for you to stand upright inside an arched greenhouse.
Framing. Materials used to build greenhouse framing generally fall into one of two categories: wood or metal. Wood must be pressure-treated, as greenhouses are moist environments that would promote rot in traditional lumber. Among metals, galvanized steel and aluminum rank as favorites due to their light weight and rust resistance. Live in a mild climate? You might consider inexpensive PVC piping, especially if you’re only seeking a temporary solution.