Equipment for growing plants as distinguished from equipment for controlling the climate is an essential aspect of gardening under glass. You will need benches or plant trays, maybe both; pots; storage space for soil and other supplies; a convenient work area for potting; a plant-propagating area; and you will find some shelves useful. Of course, there are a few necessary tools if you have a garden, you probably have all you will need of these. Then there is that overall classification of "sundries" plant tags, stakes, and other useful items to make your greenhouse work easier and more fun.
What you want to grow determines the type and arrangement of benches. For plants in beds, install regulation benches at a convenient height for working, say about 2 1/2 to 3 feet.
To make wood benches, space bottom boards of rough-sawn 1-inch-thick redwood about three-quarters of an inch apart, making the sides and ends of smooth-finished redwood. For upright and cross supports, use redwood or three-quarter-inch hot galvanized steel pipe. To insure long service in the high humidity of a greenhouse, insist on heart California redwood. Benches of standard lumber or soft wood, even when treated with a wood preservative, rot quickly. Fasten the sides and end boards to bottom boards with angle braces of hot galvanized steel.
To make asbestos cement-board benches the ideal, long-lasting type, impervious to moisture or bacteria get quarter-inch corrugated asbestos cement-board for the bottoms of the benches and smooth-finished redwood for sides and ends. Sides and ends are fastened in place with steel angle braces. Legs and cross supports are made of pipe. Corrugations (in the asbestos cement-board) running the short way across the bench provide drainage to front or back. Under-bench areas then stay dry and may be used for storage or for additional growing space.
Benches with legs precut to exact length can be ordered from greenhouse manufacturers. If pipe legs are used, split tees are furnished for quick assembly. Wood for sides and bottoms is furnished in random lengths so there will be extra material to allow for waste when benches are cut-to-fit in place. Necessary hardware and fittings are of hot galvanized steel.
If you build your own, make the side benches 2 feet 10 inches wide and the full length of your greenhouse. If your greenhouse is as wide as 14 feet, it will also accommodate a center bench make this approximately 3 feet 8 inches wide and about 5 feet shorter than the length of your greenhouse to allow space for a walk and a work area at each end.
With a supply of pipe on hand, you can also build the pipe legs, a fairly simple job, since split tees make assembly possible without threading of pipe.
At the start, line your wood benches with newspapers or burlap. This prevents soil from falling through the bottom before moisture from watering makes the boards swell enough to close up the spaces. To prevent legs from sinking into the ground (and consequent uneven settling of benches), place a brick or concrete slab footing under each support.