Wood, steel or aluminum is used for the supporting framework of greenhouses. Seasoned, construction-grade lumber should be used when building a wood framed greenhouse. When possible, rot resistant woods such as redwood and cypress should be used. If less rot resistance woods are used, they should be treated with copper naphthenate. Do not use ceosote and pentachlorophenol preservatives because they release vapors harmful to plants.
Greenhouses built with steel require constant maintenance to prevent the steel from rusting.
Aluminum is the best material to use for the supporting framework of a greenhouse. It is lightweight, strong, requires little maintenance and will last many years. Some greenhouses should be built on foundations. Others, such as plastic greenhouses, can be placed on the ground. In Florida, where the winters are mild, large concrete foundations are not needed.