Concrete shed base or gravel shed base? It's a question every shed owner asks, but the answer depends on what your needs, property and shed size and purpose are. Sheds on skids are traditionally placed on a gravel base because they are temporary structures, and so is the base. But even if a shed is not placed on skids, the shed will still need to rest on wooden formers, concrete blocks or pavers which keep the wood floor off the gravel. No matter what kind of foundation you select, make sure the ground is compacted, leveled and has good drainage to eliminate shifting and settling.
Permanent sheds and sheds with larger dimensions, sheds that hold heavy equipment such as tractors, mowers, and bags of supplies are placed on concrete bases for added support.
One of the advantages of placing a building on concrete is that the shed won't settle or shift. Settling can often cause a building to shift, making doors and windows catch or rub as they lose their plumb or true lines. Whichever base you chose, the ground will still need to be compacted and level.
Preparing Ground for Shed on Concrete
Level and compact your ground, ensuring that any water will drain down and away from the foundation. Using stakes and twine, set out the dimensions of your slab. The slab should be the exact dimension of your shed base minus 3/4 inch on all sides to allow the shed to overhang the slab. Add six inches to all sides of the dimensions where the slab will be and dig down four to six inches, depending upon the softness of the soil.
The softer the soil, the deeper the hole should be. Using a mechanical compactor tamp the ground firmly, to make it level. Use a four-inch-thick layer of gravel or substrate. You'll then build a wood mold for the next step, the concrete slab. Once the mold is in place and leveled, mix and pour your concrete, making sure to allow several days for it to dry slowly.
Preparing Ground for Shed on Gravel
Level your ground in an area at least two feet wider than your shed dimensions, so you have a one-foot border around the outside of your shed. This extra gravel border will prevent dirt from splashing up during rains, and it will help you avoid pests and rot. It should also ensure that water will drain down and away from the foundation. Dig down at least four to six inches and compact the ground, making sure it is level.
To ensure a cleaner border, install an outer frame of pressure-treated 2" x 6" wood on a vertical edge. Stake the inside of each of the corners with a 2" x 2" stake to secure the frame. Gravel will provide the base of your shed's foundation. Your shed should either rest on this foundation on skids, or on a wood frame on concrete spacers set out in the gravel.
That's all there is to it. Now that the shed base has been prepared, it's time for the construction to begin!