There are a variety of greenhouses types and an assortment of structural components and framing materials. It's important to examine and consider each type of greenhouse to see how they compare to other materials and structures. Doing so allows for the best greenhouse selection for a specific application.
Lean-to greenhouse structures are rarely used commercially, and are typically used by hobbyists. A lean-to greenhouse only has three sides, as it is made to be fastened to an existing structure. This greenhouse is less costly than most types of and is easily accessible during the winter.
Detached greenhouse structures are free standing, but have corridors that connect multiple structures together. These commercially used structures are popular and have solid walls and domed rafters.
Ridge and Furrow
Ridge and furrow greenhouses typically have a curved arch or a gable (triangular part of a wall amid an inclined roof's edges) arch. These greenhouses don't have a wall below the gutter, as it decreases effectiveness. A gutter at the eave connects multiple greenhouses together. Greenhouses with a gable arch work well for heavy construction materials, whereas curved arches can accommodate light materials.
Gutter-connected structures have at least two bays that are attached by a shared wall. These greenhouses are typically used commercially. Double layers of polyethylene film cover gutted connected greenhouses.
Rafters are the main reinforcement of a greenhouse. Depending on the necessities, the rafters are positioned on 2 to 4 foot centers. Purlins support areas between rafters, and are typically spaced 4 to 8 feet apart. Cross ties can be connected to purlins in order to supply extra reinforcement. Additional structural components are columns and side posts. The height of these components varies from 1 to 10 feet. Columns and side posts are important components have an effect on the efficiency of the greenhouse.
The most popular framing materials are wood, steel and aluminum. Aluminum is the most inexpensive of the three and lasts longer. Aluminum also can be pressed into an assortment of shapes and width. Wood degrades faster, so it's used less often. The faster degradation is due to the moist environment in the greenhouse. If using wood, be sure to use pressure-treated wood that withstands decomposition.