Now that you have decided to have a greenhouse, you will want to investigate the numerous types and styles offered by various firms-some long established others comparatively new offering the latest in greenhouse construction. If you have nurtured your desire for a garden under glass for some time, you will probably have definite ideas as to just where and how you would like to build it. You will do well, however, to make haste slowly and not to let yourself be carried away simply because you have finally made the momentous decision.
First send for the catalogues of two or three firms whose advertisements you will find in garden magazines or online. Study these catalogues, noting particularly the construction features stressed by each manufacturer. You will find that some features are exclusive with certain firms, that some seem to be offered by all of them. Yet there will be small differences in construction that can make one greenhouse superior to others for your particular use.
You may be surprised by the number of types, styles, and sizes of greenhouses available. Perhaps you will be perplexed by the jargon of the trade: ridge refers to the central and highest member of the roof of the glass structure; the eave is the definite break your eye encounters as it travels from ridge to ground.
In standard construction, an unbroken line goes from eave to sill. The sill rests upon a wall that may be made of masonry (poured concrete, cement blocks, cinder blocks, bricks, or decorative rocks or stones set in concrete); of wood reinforced with steel; or of wood reinforced with wood. All kinds of walls, including the glass sides of a glass-to-ground design, rest on footings, which may be of poured concrete, steel, or redwood or cypress. Footings extend from grade (ground level), or a couple of inches above grade, down to frost level or a few inches below frost level. Your local building department will tell you the official frost level for your area; if your building codes require that you have a permit to erect a greenhouse, your footings must go down to the official frost level, and they should anyway so that alternating freezing and thawing of the ground will not heave your greenhouse up and out of alignment.