How to Build a Shed Base

Added by Shaun Wheatcroft
  • DIY
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billyoh 20 classic 6x6 windowed shed 01 x How to Build a Shed Base
Shed pictured: The BillyOh 20 Range


A shed base is an essential past of building a shed, the base has to be properly made to give your shed a solid foundation. On the face of things, building a shed base might seem like a daunting task, but follow these simple steps and you’ll have a level and sturdy base for your new shed in no time at all.

Plan Where Your Shed Will Be Located

  • Make sure there’s access (for delivery and access to all sides for maintenance and applying wood treatments etc.)
  • Surrounding area conditions (Foliage, young trees that may grow in the future)
  • Natural light (a well-lit area is best if the building is to be used as a workshop for example)
  • The view of your garden from the planned area (for summerhouses etc.)
  • Consider whether you intend to run an electrical supply to the building.

Choose the Type Of Base

It’s crucial to provide a level and dry foundation for garden sheds. Never assemble a shed on an unsound base, otherwise you are running the risk that screw holes connecting the wall panels will not line up. For larger buildings, especially if you’re going to use the shed as a workshop, a full concrete base is your best option. However, generally there are two types of shed bases suitable for a garden building, consider which is best for you…

So what are the choices? There are three main popular types of shed base

  • Eze Base
  • Concrete Base
  • Paving Slab Base

Note: Whichever method is more suitable for you, we recommend that you have a 2-inch (5 cm) lip around the base of your shed. To calculate the size of base required for the particular building you wish to build, add 4 inch to the overall base dimensions to ensure an adequate base size for your shed.

How to Build an Eze Shed Base

Many garden sheds come with option to purchase an Eze base. This is the easiest and quickest option, make sure the ground you are laying your base on is flat and level. It is recommended to lay your Eze base on top of a concrete or paved surface. Watch the video guide below:

How to Build a Concrete Shed Base

Equipment Checklist

  • Pegs and string
  • Building sand
  • Standard cement (all-in ballast, cement & water)
  • Timber for base formwork
  • Tape measure
  • Spade
  • Sweeping brush

1: Mark out your base

Decide where to position your garden shed, allow enough distance from hedges or fences for easy access to all sides. Using the pegs and string, mark out the base 2 inch (5 cm) larger than the area of the building on each side. Finally, measure diagonally across both sides to ensure the area is square.

1 How to Build a Shed Base

2: Level Off the area

A concrete requires 3 inches (7.5 cm) of compacted hardcore (all-in ballast or other crushed rubble/gravel) underneath the 3 inch concrete layer. The base can be level with the ground or raised above it. If you want it to be level, excavate the top earth to 6 inch (15 cm), to allow for the hardcore layer and 3 inches (7.5 cm) of concrete. Level the area with a rake and spade and remove the pegs.

3: Create a Levelled Hardcore2 How to Build a Shed Base

Set up a levelled formwork. This involves measuring, cutting and fitting timber to the shape of the base in order to contain the concrete. Check diagonal measurements to ensure the formwork is square and level, as this will determine whether your shed base is 100% sturdy. Next, spread a layer of well compacted hardcore (all-in ballast or crushed gravel) and cover with a liberal amount of sand. This needs be well compacted and flattened down, preferably with a compacting tool or roller.

4: Add the Concrete

Mix concrete using one part cement to five parts all-in one ballast, or use bags of dry-mixed concrete and just add water. 3 How to Build a Shed Base

Remember small amounts of water should be added at a time and mixed into the concrete. Be careful as excessive amounts may make the cement too sloppy and it needs to stay reasonably dry. Spread the concrete evenly and slightly above the formwork. This can be then levelled off with a long straight edge of timber resting on the formwork using a sawing motion slowly (as shown below) over the entire surface of the freshly laid concrete.

If wet weather is forecast, cover the concrete with polythene for 24-hours. In warm weather, cover the base with damp sacks and sprinkle them with water over the 24-hour period, this will ensure the drying concrete will not shrink and crack. The result is a smooth, sound, level base. The perfect foundation for the construction of a garden shed.

How to Build a Slab Shed Base

Equipment Checklist

  • Pegs and string
  • Flat Face Paving Slabs
  • Building sand
  • Standard cement (All-in Ballast, cement & water)
  • Rake
  • Tape measure
  • Spade
  • Rubber mallet
  • Sweeping brush

1: Mark our your base4 How to Build a Shed Base

Decide where you will be placing your garden shed, leaving enough space from hedges, fences and boarder for easy access to all sides.
Using pegs and string, mark out the base 2 inch (5 cm) larger than the area of the building on each side. Finally, test the size by measuring the two diagonals to ensure the area is square.

2: Dig, level off and rake the area

Strip the topsoil and dig out to a depth of approx. 2.5 inch (7 cm) to accommodate the base. Level the area with a rake and remove the pegs.5 How to Build a Shed Base

3: Mix the cement

Mix together one part cement to eight parts building sand for a dry sand and cement mix. Spread this evenly, ensuring that the mix sits approx. 4 cm in depth. Ensure that it is level.


4: Lay the paving slabs6 How to Build a Shed Base

Starting from one corner and working outward, lay the slabs by tapping down on the centre of each slab with a rubber mallet. Using a spirit level, ensure all the slabs are square, level and firmly butted together for a solid base.


5: Double check the base is level and flat

The completed base should now be level and square. Conduct a final check with a long straight edge piece of timber to check if the base is level from each corner and also measure the diagonals to finally check that the base is square. Brush off any excess dry sand/cement mix, which could hinder the levelling of the shed. The result is a smooth, solid and level base.


Frequently Asked Questions

Will I need help to build my base?

Constructing the foundation for your garden shed is a fairly hassle-free task for a single person to complete. When it comes to actually assembling the shed, we do recommend an extra person is on hand for lifting and placing roof and wall panels in place.

Do I need planning permission for my shed?

Planning permission is not normally required for construction of a garden building, unless you live in a conservation area or the building could intrude on a neighbours garden. You may wish to check with neighbours or local council before construction.


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Added by Shaun Wheatcroft / 
Shaun Wheatcroft is the community blogger of Garden Buildings Direct. Come and say hi!
  • Celinda

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  • Matt Hubert

    Very informative post, the basic you have mentioned here about “How to Build a Concrete Shed Base” is really very helpful for the contractor. Even if any household thinking to build a concrete shed base by their own, they can do it easily by referring to your post.

  • Caren42Qogqgf

    Hurrah, that’s what I was looking for, what a information! existing here at this weblog, thanks admin of this web site.

  • James

    Hi Shaun – thank you very much for your informative Blog about building a shed base. I am building one using your paving slab guidelines but have one quick question – what type of sand should I use for the Cement mix – Buidling sand or Sharp sand? What exactly is the difference?

  • Tim

    putting felt on the roof on a billyoh 4000 16 x10 feet – as the roof is so high and the long sides, can I put my weight on the roof to knock in the tacs on the felt, if I cant put any weight on roof – how do I attach the felt?

  • pace

    Please, is it possible to put a damp proof membrane under the slabs intended to be used as a shed base? Thanks

  • andy

    Hi got a 6 X 10 shed on paving slabs but not level so I’m getting 10 X 10 shed need to make a concrete base removed slabs how deep do in need to dig out and how much cement and Balast would I need ty andy

  • Sam Wardill

    What thickness of concrete would you have typically for a shed? Is it usually worth hiring a concrete mixer?

  • lin

    Getting a 12×10 summerhouse and wanted to know if it could be set on a raised platform (approx 12″). This is because the land gets very wet. Your help and advice would be appreciated. Thanks, Linda