A lean-to greenhouse is an attached greenhouse that is built against a building, garage or house, using the existing structure for one or more of its sides. It gets its name because it is supported by another structure that it seems to “lean” on. It is usually an extension of the existing building or is designed and added to a new building.
The lean-to greenhouse is generally made up of three walls, a door, some ventillation, and a sloped roof. A lean-to structure is usually built on the south or east side of a building, to get maximum exposure to the sun. The location of windows and doors of the supporting structure is also kept in mind when building a lean-to structure, to avoid the risk of snow, ice or heavy rain sliding off the roof or the house onto the structure. You can access such greenhouses from the within the house without having to go outside, using a doorway in the supporting wall that connects it to the house.
Their main advantage is that lean-to greenhouses are closer to available water, heat and electricity. Therefore the cost of heating a lean-to greenhouse is lesser than heating a freestanding greenhouse of the same size, as one side of the lean-to greenhouse is attached to an existing wall and no separate installations for water and electricity are required.
Their disadvantages include limitations on space, sunlight, ventilation and temperature control. Temperature control is more difficult because the supporting wall may collect the sun's heat but the translucent covers of the greenhouse will lose the same heat rapidly. Their size is also limited by the size of the walls of the supporting structure. Another disadvantage when compared to freestanding structures is that these greenhouses do not get adequate sun exposure during the day if they are built facing another direction due to space limitations.
Lean-to greenhouses are available in various sizes and structures to suit different climates, individual needs and budgets. They are primarily designed for people with a limited space for gardening and are considered to the cheapest option for a gardener who wishes to expand his interest.