Concrete Shed Base

How To Make A Concrete Base For Your Shed?

The base is a key part of your shed or garden construction. It keeps your garden shed safe from water, bugs, and other damage, and it provides a secure place to stand. If you plan to keep your shed, summer home, or log cabin for a long time, you should go for a concrete shed base. Further, concrete bases are better than other options, even though they’re simple to build.

Everything You Need To Create A Concrete Shed Base

  • Ballast, cement, and water (or ready-mix concrete)
  • Compacted hardcore or brick rubble
  • Earth rammer
  • Cement/concrete mixer or cement mixing tray
  • Tape measure
  • Spirit level or set square
  • Shovel
  • Rake
  • Tamping board
  • Edging trowel
  • Wheelbarrow and/or cement mixer
  • Plastic sheets and wooden supports
  • Breeze blocks or bricks
  • Saw
  • Pegs and string

Now that you have your list let’s get started!

A Checklist of Building Concrete Shed Base

If you already know the amount of concrete you need and the cost, or if you already have it, skip to step 2. If you’ve already picked the right location, proceed to step 3.

Step 1: Calculate the quantities and costs

It’s logical that the larger your garden building, the bigger your base, which means you’ll need more concrete, and it will cost more.

We recommend a concrete base about 30-40cm (12-16 inches) larger than your shed’s dimensions. For example, if your shed is 8×6 feet (96×72 inches), you need a base around 9×7 feet (108×84 inches).

Concrete mix for the shed base

To calculate the concrete needed, work out the shed’s dimensions. For a shed base at least 75mm deep (suitable for most garden sheds), use this equation: Depth x width x length = concrete amount. 

If you’re using ready-mix concrete, you don’t need to worry about sand and cement quantities. But if you’re mixing concrete from dry sand and cement, you must factor in the cement, aggregate, and sand. Further, to calculate the mix, use a ratio of one part cement to five parts ballast (a blend of sand and aggregate). One can buy 40kg bags of ballast at DIY stores.

The cost of concrete can vary due to factors like availability, inflation, and more. For accurate cost information, you can use the concrete shed base cost calculator on various concrete suppliers’ websites.

Step 2: Choosing the Right Shed Location

To find the best spot for your shed, consider what you’ll use it for and picture it in your mind for easy access. Once you’ve laid a concrete base, it’s challenging to move, so getting the location right is crucial. Moreover, before you lay the concrete, there are a few things to be certain about:

  • Level ground: Find an area as flat as possible to prevent misalignment of the panel screw holes and avoid the hassle of levelling a concrete base for shed on uneven ground.
  • Avoid wet areas: Building on swampy or excessively wet ground can lead to moisture damage to your shed and its contents.
  • Watch out for trees and foliage: Trees and overhanging foliage can block light and lead to moisture build-up, so steer clear of them.
  • Avoid shaded spots: Also, ensure your shed gets sufficient natural light, but be cautious about excessive direct sunlight causing overheating.
  • Leave space around: Moreover, maintain at least one meter (approximately 3 feet, 3 inches) between the shed and fences or walls to facilitate construction, access, and maintenance.

Step 3: Clear Vegetation

Remove weeds and grass from the area where you’ll lay your base. It prevents air pockets in the concrete and helps keep moisture away from the shed, extending its lifespan.

Step 4: Mark the Dimensions

  • Now, use a tape measure, pegs, and string to mark out the dimensions of your base. 
  • Make it 30-40mm larger than your shed on each side for a proper fit. 
  • One must ensure the area is square and level by measuring the opposite lengths; they should be equal.

Step 5: Excavate and Level the Area

  • To create a level base, dig the marked area to a depth of six inches (150mm). 
  • Add about 75mm (three inches) of compacted hardcore or brick rubble as the foundation, leaving room for 75mm of concrete on top. 
  • If needed, add compacted sand for further levelling. 
  • Now, compact the stone/sand with an earth rammer to firm up the base before removing the pegs.

Why avoid laying the concrete base on soil? Because it’s not advisable to build a concrete base for shed on soft ground, you need a proper sub-base.

Step 6: Construct the Shed Frame

The shed frame, also known as timber rails, serves as a containment for the concrete as it solidifies, preserving the base’s shape. To build this frame, match its inner dimensions to the base’s. Moreover, make the frame approximately 100mm (about 4 inches) thick and use a spirit level or set square so it’s level all the way around. It guarantees that when the rails are filled, the concrete remains level all around.

Step 7: Pour the Concrete

To lay the concrete, pour a layer of it into the shed frame:

  • Spreading it evenly 
  • Making sure it reaches the corners and edges

We recommend applying the concrete one layer at a time until it slightly overflows the frame. While pouring, use the tamping board to compact the wet concrete. Also, carefully move back and forth over the entire surface with the tamping board until it’s flush with the top of the frame, using a spirit level to help achieve this.

Step 8: Smooth the Edges

Once satisfied with the finish, use the edging trowel to round off any rough concrete edges and prevent potential chipping.

Step 9: Protect the Concrete Shed Base

To safeguard the drying concrete from cracks, place wooden supports and cover it with a plastic sheet. Additionally, you better secure the sheet with breeze blocks or bricks.

How long does it take for a concrete shed base to dry?

Allow the concrete base for shed to set for a minimum of 48 hours before starting to build your shed on it. If you’ve constructed the base during warm weather or it becomes warm during the drying period, consider the following:

  • Spraying the base with water 
  • Covering it with a damp cloth 

It will prevent cracks from forming. With your concrete shed base ready, you’re now prepared to assemble your shed.

Pros Of Concrete As A Base For Your Project


Exceptionally strong

Concrete is sturdy and practical, and it’s all around us!

A concrete foundation is just as robust as long as you don’t try to damage it. It provides an almost unbreakable base for any shed, outperforming other options regarding reliability and durability.

Weather and water-resistant

A concrete base can withstand any weather, whether it’s rainy, sunny, or even in harsh winter conditions. Since concrete is impermeable, it remains dry and impervious to water. Also, any water landing on it will simply run off, and moisture trying to seep from below is rejected.

More durable compared to other options

Thanks to its strength and resistance, concrete outlasts other materials. Erosion may occur over many years, but the slab retains its strength and stability, possibly lasting up to a century.

Support heavyweights

Concrete bases are capable of supporting substantial weights, making them ideal for:

  • Storing large items 
  • Serving as a base for extensive garden structures

Cons Of Concrete As A Base For Your Project


The most expensive base material

Concrete foundations are undeniably the costliest option. Besides the high material cost, hiring someone to install the base can also be expensive. Even if you opt for a DIY approach, it still demands significant time and effort. Also, some may find satisfaction in the task, but it can be pricey if you prefer not to lay a concrete slab yourself.

Difficult to alter or remove

If you decide to stop using your shed or garden building, removing a concrete base can be difficult due to its durability. Calling in a professional is often the best option, but it comes at a cost.

Environmental impact

Using concrete is not environmentally friendly. Cement, a key component of concrete, is a significant source of carbon dioxide emissions, contributing to global warming. Further, using concrete as a hard surface also has various direct environmental consequences.

Ending Notes

With your concrete foundation ready, the next step is to start constructing your shed. But where do you find the concrete to begin your project? It’s simple – Pro-Mix Concrete offers top-quality concrete in various locations across the UK. Place your order today!