What Is a Good Base for a Shed?

Locale Affects Base

• Location will affect the decision on what kind of shed base to build. Locales subject to high humidity and termite infestations need a masonry base to prevent rot and insect damage. Areas with sandy soils or ground subject to movement from freezing and thawing may benefit from a pier and beam base. This type of base can minimize problems from ground movement, which might crack a concrete slab.

Gravel Starts a Good Base

• Almost all sheds should be built on a base of firm ground with foundation elements set in compacted gravel for good drainage. Even concrete piers or posts set deep in the ground in concrete will benefit from gravel under and around them to allow water to drain away. Some sheds can be built on bases of compacted gravel with wooden skids or railroad ties set in place on the gravel to support a floor.

Size and Use Affect the Base

• The size and purpose of a shed will affect its base. A bigger shed will weigh more and need more base support. A shed intended to hold lawn tractors and other large implements will require a stronger base than one built to hold only basic garden tools and objects such as bicycles. Big sheds generally need a concrete slab base or concrete piers with 4-inch by 4-inch or 6-inch by 6-inch beams for floor joists.

Some Bases Float

• Some sheds are built on "floating" foundations, a variation of pier and beam construction. Floating foundations use many concrete piers with special metal tops built in that hold 2-inch joist boards. These piers are set on level ground and are leveled by length and width. Upright joist boards are set in the piers on edge and covered with heavy flooring, 4-foot by 8-foot panels of 3/4-inch plywood or 2-inch by 6-inch boards. This works well on solid soils and areas where water needs to flow under the shed to drain properly.