A skid foundation provides one of the simplest foundations for a small garden or storage shed. Construction requires only basic carpentry tools and a shovel. The foundation is constructed of standard materials available at all lumberyards and home improvement stores. The task falls within the abilities of most do-it-yourselfers with basic carpentry skills and equipment.
Excavate the sod from the planned site of the shed. Fill the area with gravel to a point level with the surrounding sod.
Cut 6-by-6-inch treated beams to the same length as the shed. Cut the beams with a reciprocating or circular saw. Make two cuts, one from each side, with the circular saw. You will need one beam for every 3 to 4 feet of shed width.
Place a beam 6 inches from each planned side of the shed. Place additional beams between the first two spaced equally about 3 feet apart.
Level the beams in place. Start on one side and level that beam using a 4-foot carpenter's level. Move gravel as needed to level the beam. Once that beam is level, use the carpenter's level to position the next beam. Place the carpenter's level between the two beams and adjust the gravel under the second beam to level it with the first beam. Continue the process across all the beams of the shed base.
Build the floor joist assembly. Start with a frame of 2-by-4-inch lumber the size of the planned shed. Place a floor joist every 16 inches between the two long sides of the shed floor frame. Nail the frame and joists together with 16d nails.
Place the floor joist assembly on top of the beams. Check the level one last time before toenailing, nailing at an angle, through the floor joists into the beams
Compact the gravel using a plate compactor before levelling in the beams for a more secure work surface.
This type of shed base only works on surfaces that are basically level to begin with. A slope of an inch or two can be worked around, but larger slopes cause problems for skid shed foundations.