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How to Build a Foundation For Your Shed

Do you know to do build a foundation? Our free article center was formed to help you build, plan, and execute your wood working project as smoothly as possible.


How to Build A Foundation for a Shed
Written by Frank McGill.

One of the most important steps in building a great shed, is understanding how to build a great foundation.  There are several types of foundations to choose from, and it depends entirely on your different needs for your shed, as well as your location, and budget.  You can choose any of these foundations to build your shed or gazebo that you choose from our Complete Shed Plans or Gazebo Plans Package.

Wood Skid and Wood Floor Foundation.

This type of foundation is the cheapest and easiest to do.  It works fine for a storage shed in a mild climate on relatively stable, solid and flat ground.  It is also a great foundation if you plan to move your storage shed sometime down the road to another spot in your yard, or to another property all together.  Just follow these easy steps:

Site Preparation.  Prepare the site by scraping away all grass or weed material covering the shed area.  If your soil does not drain well, remove 4" to 6" of earth under the shed area and replace with 4" of pea gravel to increase drainage.  Otherwise you can simply dig a drainage trench approximately 12" wide by 6" deep where the 4"x6" skids are to be placed.  Fill the drainage trench with gravel to unsure good drainage and to minimize the wood to soil contact.

Placing the skids.  Skids should be either pressure treated or redwood to prevent decay from ground contact.  Position the 4x6 skids and make sure the skids are level (see diagram below).  Tie the skids together by nailing the outer floor joists to the front and rear rim joists.  Toe nail the other joists to the skid.  If you want to incline the shed floor slightly to ensure drainage, you should raise one end of both skids by an equal amount (1" for every 8' of skid) by placing additional gravel under the skid.

Constructing the floor frame.  Having nailed the rim joist to the skids, you should now check that the floor frame is square.  You can use the 6-8-10 method we have discussed in our other articles to ensure squareness.  Complete the floor framing by adding the remaining 2x8 floor joists placed at 16" on center.  Connect the floor joists to the rim joists with at least 3-16d coated sinkers at each end.  If your budget allows it, use metal joist hangers to add extra strength to your floor framing.

Adding the floor framing.  For extra strength and durability, use 4' x 8' x 3/4" tongue and groove extra grade plywood for flooring in your shed.  For normal use, install 4' x 8' x 3/4" CDX plywood to construct your floor.  Fasten the floor framing to the floor joists using 8d nails 6" on center at the edge of the sheets and 10" on center along the intermediate floor joists.  Take care to construct a stable and even floor which will serve as the foundation for your wall sections.

wood skid foundation shed plans


Concrete Pier and Wood Floor Foundation

This is the next step up from a wood skid foundation.  It takes a little more work, but your foundation is much more solid here.  Also, if your location is particularly damp, this foundation will protect your shed floor that you worked so hard to build.

Site Preparation.  Prepare the site by scraping away all grass or weed material covering the shed area.  If your soil does not drain well, remove 4" to 6" of earth under the shed area and replace with 4" of pea gravel to increase drainage.

Locating the Piers.  You will need to use your batter boards, that we have discussed in a previous article, to stretch a nylon string along the imaginary outer wall line.  Use this string line o stake the pier location at 4'-0" on center.  The piers will support either a 4x6 beam or a built up beam made from two 2x6's.

Pre-cast Piers.  If you are using precast concrete piers with an attached wooden nailer, you need to dig a pier footing at least 14" wide and 6" deep.  The depth of the footing should be at least 6" below the local frost line.  Pour the concrete into the footing hole.  Spray the pier with water and then embed the pier at least 3" into the fresh concrete and twist slightly to achieve a solid bond between the pier and concrete.  Make certain that you have enough concrete in the hole so that the top of the nailer block is at least 4"-6" above grade level.  Check the alignment of the pier by dropping a plumb bob from the centerline string.  Finally, use a level across the block and tap the pier until it is level in all directions and square.

Attach the beam support posts to the piers.  Cut 4x4 beam support posts to place the floor at a height above grade determined by local codes.  If you don't require posts, simply toenail the 4x6 beam into the precast pier nailer blocks with 12d coated sinkers.  If you require a certain grade to floor clearance, toe nail the posts into the nailer and then use a post cap connector to secure the beam to the post.

Constructing the floor framing and the floor.  At this point, the process is the same as with a wood skid foundation.  You start at the outside joists, and work you way to the cross support joists to build your shed floor.  The picture below shows a plank floor, but you can also use plywood for a cheap shed floor.

concrete pier foundation shed plans

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