How To Build A Shed Foundation

Shed foundations on Wood Rails, Concrete Blocks and Concrete Slabs

This tutorial shows you the steps to building a wood rail foundation, from cutting the rails and installing them on the ground to making them square and level.


How to build a shed foundation cutting the foundation rails
The first step is to cut the foundation rails to the length shown on the plans and then locate them on the ground where they will be permanently installed.

Locating them on the ground is done by setting the rails in their approximate location and checking them for square.

To check that the rails are square in relation to each other you will first make sure that they are the proper distance apart from each other and then measure diagonally from corner to corner.
Your goal is get both of the diagonal measurements to be the same length. So move the rails parallel to each other until the measurements are the same.

The locations of the rails only need to be within a few inches of perfect as you will be moving them to prepare the ground underneath.



How to build a shed foundation digging the rail beds

The second step is to prepare the rail beds. This is done by making them level with each other and themselves.

How to build a shed foundation level the foundation

To check that the rails are sitting at the same height in relation to each other you will use a straight board and a level. Set the board so that one end is on one rail and the other end is on the other rail. Put the level on top of the board to check which rail needs to move up or down.

You will need to repeat this process several times as you adjust the rail bed levels until the rails are the same height as each other and the rails are level in their own beds.

On slightly sloping ground you may need to dig holes or build up the lower areas with gravel to allow the rails to sit level. This shed required that the higher rail be dug down to the height of the lower rail that was sitting on top of the ground.


How to square a shed foundation
The third step is to get the foundation rails parallel and square with each other. This is done exactly the same way you located the rails the first time by using a tape measure to check the locations of the rails.

It is usually easiest to get one of the rails sitting where you want it, and then adjust the second rail so it is parallel and the correct distance from the first rail.

You will need to repeat the measurement checks and adjust the rail locations until they are correct.

Although it is not shown in this tutorial because this shed will be moved to another location, each rail should have a few inches of gravel under it. This gives good drainage under the rails and makes it easier to level the rail beds.

Once the rails are square and level you are ready to set the floor joist on them.

Need A Different Shed Foundation?

What are the other shed foundation options.

A treated wood rail shed foundation is not always the best choice. There are several other foundation types to choose from depending on your needs and the terrain you are building on.

Lean To Shed Roof

Post and Beam: The post and beam shed foundation is great for sloping lots or where you simply want the shed off the ground. It consists of concrete piers installed along the roof bearing walls. A beam is installed on the piers and then the floor joists are either set on top of the beams or hung between the beams as shown in this photo.

Gambrel Shed Roof

Concrete Slab: Pouring a concrete slab is the best way to get a very solid floor. The cost is typically very close to a framed floor, just a bit higher. A concrete slab should have a deeper footing around the perimeter to hold the weight of the walls and roof. The shed walls are held to the concrete using bolts spaced along the wall.

Treated Floor Joists On A Gravel Bed: This is one of the simplest ways to install a shed floor. A 4 inch deep gravel bed is installed and leveled and the treated floor joists are set on top of it. Make sure you have good drainage away from the foundation and this shed floor will last the lifetime of the shed. This system also keeps the shed floor level close to the height of the adjacent ground.

Garden Shed Roof

Treated Wood Rails On The Ground: Treated lumber is rated for direct ground contact. So this system works well when you want to build the shed floor using untreated lumber. The wood rails are set on the ground, or preferably on a shallow bed of gravel, and then the floor joists are set on the rails. Make sure that the wood rails are set under the walls that support the roof.


phone and email questions about shed plans and shed building how to build a shed
phone and email questions about shed plans and shed building how to build a shed

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