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How to Build a Concrete Base for Your Timber Garden
Shed
Instead of using concrete blocks you might choose to prepare a concrete base for your garden shed. This is a more
attractive and permanent foundation, and has the added benefit of preventing weeds from growing under the
shed.
Here we provide simple step by step instructions for preparing a concrete base for your
timber garden shed.
Select the location:
Choose the location in
your garden where you intend to put the shed. It is important to leave enough room between the shed and any walls,
tree or other immovable obstacles to walk around the shed. You will need to access all sides of the shed for
maintenance.
Mark out the Area
Mark out the size and shape of the shed using pegs in the ground and string. The size of the base should be
approximately six inches wider all around than the size of the shed. Check that the corners are right angles, and
the opposite sides are the same length. If the rectangle is correct the distance between diagonally opposite
corners should be equal.
Dig out the Surface
Dig down and remove the surface soil to a depth of four inches minimum. Try to make the bottom of the hole as level
as possible. If the ground on one side is higher than the other you will need to go deeper on that side. If the
ground is not level you will require more concrete as the hole will be deeper on the higher side. Make sure the
boards you use are wide enough to accommodate this.
Create the Frame
Use four boards to make a
frame. They should be assembled into a rectangular shape, and held in position with pegs stuck into the ground
outside the frame, or you may choose to nail the boards to each other for a sturdier frame. Lay a fifth board
across the top from one corner to the diagonally opposite corner, and nail it to the 2 boards underneath at each
end. This is to prevent the boards from moving when the concrete is poured. When you are nailing the boards
together it is a good idea to leave the end of the nails sticking out a little to make it easier to pull them out
when you are finished.
Pouring the Concrete
Dampen the hole slightly before you pour in the concrete. Prepare the concrete according the manufacturers
instructions, ensuring that you have enough to fill the hole to the required depth. Pour the concrete into the hole
and use your shovel to move it around and make it level. It is important that the concrete fills the frame to be at
least two inches higher than the surrounding ground at any point. Tap the surface of the concrete, and the frame
around it to consolidate it and release trapped air bubbles.
Level the Concrete
Use the side edge of a straight piece of timber to move back and forth with a sawing motion across the surface of
the concrete to make it level. Use a trowel or float to smooth the surface, sweeping the flat edge over the surface
in wide arcs. Leave it to dry until the surface water has evaporated and then smooth the surface again.
It is important to get the surface as level as possible as you do not want water lodging on it. In
particular, check that the places where the garden shed supports will go are definitely not lower than the concrete
around it, as you do not want the garden shed supports resting in puddles.
Remove the Frame
The concrete takes around twenty four hours to cure, but can vary, so check the manufacturers' instructions. Once
it has set, you can dismantle the frame pulling it out and away from the concrete. Use the excess soil you
dug up to make the hole and fill in the space around the concrete base so that the surrounding
ground is a few inches lower than the concrete base. Once the concrete is fully set, you can go ahead and
order the garden shed.
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