All garden sheds need a base or foundation for the structure to rest upon. Shed kits using steel, vinyl or wood do not include a base. Therefore, a garden shed base or foundation must be built before you begin to assemble the shed. If you make your own garden shed plans or purchase them, you must do so before you decide to build the base.
The kind of base you choose to make may depend on (a) land form, level or sloping area, (b) type of soil, sand or solid clay, including drainage, (c) weather conditions such as very dry, heavy rainfall, severe frost or high winds, and (d) size of structure, large or small.
A foundation made of poured concrete or cement blocks to form a wall under the perimeter of the shed might be your best choice for a large building or areas subject to poor drainage and severe weather conditions. The floor area can be left as dirt or made of poured concrete or wood after the structure is built. The building suppliers can give you all the information as well as materials needed to build a concrete or a cement block foundation wall.
For a smaller garden shed and where the area is quite level, a slab of poured concrete on several inches of gravel or crushed stone makes a very solid and durable base. A building anchored to this base can withstand extreme weather conditions. Furthermore, it provides a smooth and solid floor area for storage and work space.
A simple base can be made by laying cement or sidewalk slabs on several inches of gravel to form the perimeter of the shed. On top of the slabs, build a framework of treated 2″x6″ lumber and nail sheets of waterproof 5/8″ or 3/4″ plywood on top of the framework. This is ideal if you prefer a wooden floor. In high windy locations the base should be anchored to the ground with heavy stakes or steel rebars.
Remember, choosing a garden shed base is part of the planning process, whether you plan to purchase a garden shed kit or build a garden shed from scratch. Building suppliers are quite eager to help you to decide on the best building plans. There is also a good deal of information on the internet.