A shed is a great addition to a yard. It can provide space for potting plants and storing garden accessories or storage for tools, toys, out of season items or other objects. A shed can be a 4-by-4-foot tool bin or a 12-by-16-foot workshop. A shed can be built almost anywhere; the ground does not have to be perfectly level, but the foundation must be. Check building regulations; larger sheds will require permits.
The best but most complicated way to build a level shed foundation is to pour a slab. This requires excavating the area, laying a gravel base, building wooden forms and pouring and finishing concrete. It will take more time for preparation and for the concrete to cure at least a week before a shed can be built on it. A level slab can be built on any firm ground that does not have a steep slope by varying the depth of the slab.
An easy way to level a shed area is with gravel. Mark out the shed dimensions and excavate the area about 6 inches deep. Outline the shed area with some edge restraints of plastic, metal or wood. Fill the area with gravel and compact it with a hand tamper. Vary the depth to get the top level. Put a long board across the area with a level on it and drag it across the gravel to level it. Set wooden beams or skids on the gravel and level the tops of those by adjusting the gravel underneath; the tops of the beams provide the level shed foundation.
Another way to level a shed base is with concrete blocks. Outline the shed area and rake it fairly level. If the slope is fairly steep, dig out an area at the front of the shed. Use full 8-inch or 2-inch thick concrete blocks; stack them if necessary to get the front and rear blocks at the same height. Set nine stacks for most sheds, three on each side and three in the middle. Adjust the dirt until the tops are level. Put a long board or beam on top of the blocks with a level on it to get the foundation level in all directions.
Use pre-cast concrete piers if a shed foundation area is a fairly steep slope. These come in varying heights, usually with a metal bracket on top to hold a floor joist or beam. Measure the slope to determine the different heights needed. Dig a hole for each pier, put a gravel base in it and set each in place. Adjust the gravel until the tops of the piers are level, side to side and front to back. Set joists in place and double-check the level.