How to Build a Shed Base: A Guide

If you’re thinking of adding a garden building to your backyard, then you’ll want to know how to build a shed base.

So whether you’re installing a log cabin or a garden shed, there are four steps you need to take. In this guide, we cover everything from positioning to base options and building. Keep reading for a step-by-step guide on how to build any number of shed bases.

Step 1: Plan Where Your Shed Will Go

It may surprise you that the first step of building a shed base doesn’t have anything to do with building. Before you even think about choosing a base, you need to weigh up your options.

And that means deciding where to put your shed. For example, there’s no point having a workshop with dual entrance if you can’t use both entrances!

Below, we’ve come up with some areas to consider, but to get an overview:

  • Make sure there’s clear access for delivery and maintenance work.
  • Consider the state of surrounding plants and what you might want to grow.
  • Consider things like the view of your garden, how easy it’ll be to run electricity etc.

Now let’s break those points down into sections.

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Surface

As well as suitable materials for your shed base, you also need the right surface. We’ll get onto level ground in a moment, but for now just know that a good surface:

  • Won’t be an area of pooling groundwater.
  • Won’t be at the bottom of a slope or by a ditch
  • Won’t be rocky.

And to tick all these boxes, you’ll need to consider…

Your garden

Does your garden slope away from the house? Where are you going to get the best natural light into your garden building? Remember, although building a shed starts with the base, you think to think ahead as well.

location location location three road signs
Credit: Clarendon

Location

If, for example, you’re installing a summer house, think about where you’ll get the most natural light.

If you’re building a workshop think about facing away from the elements or at least into a cool breeze for work during summer.

Uneven Ground

And if you want to keep your shed base level, then you need to start with a level surface.

Now, it’s unlikely that you’re going to have a stable base without doing something to make your ground level. You can either build up or dig down. We’ll get into these options in a moment.

But for almost all shed bases, you’re going to want to start by levelling the site of your proposed garden building. Depending on what tools you have handy you can do this with anything from a loam leveller or a garden rake to a wacker packer.

Delivery

Remember to leave enough space for the panels of your BillyOh shed to be delivered down any side access. And always bend your knees when lifting heavy objects (although our drivers will unload your garden shed for you!).

foundation scrabble pieces

Step 2: Type of Base/Type of Foundation

Now that you’ve got a level and marked out area to work with, you need to settle on a type of foundation.  From concrete to a gravel-filled base, your choice of foundation may vary on the size of your garden buildings.

For example, a multiroom garden office will require something more substantial (like concrete) than a small overlap shed.

Timber Frame (or sub-floor)

A timber frame is one of the most popular and economic types of base kit for a garden shed. Simply made of straight pieces of timber, cut to size and assembled within a wooden base, it offers a sturdy base and raises your shed away from the moist ground.

Floor joists can then be laid on top of and nailed or screwed into these timber bearers. At each corner of the timber base, simply drive stakes into the ground and secure them to the wooden frame. This will ensure your shed base doesn’t move when building on it.

Concrete Base

A concrete floor is a much more permanent solution. But it’s also more expensive. With a permanent foundation, you’ll be able to raise your garden shed up from rising damp and provide a long-lasting base.

A concrete foundation may require some more expertise or even hiring someone to pour it, however. These sorts of jobs do require cement mixers at the very least!

To pour your own concrete slab, you’ll need to:

  • Level the shed site
  • Set up boxing around the pour perimeter
  • Lightly soak the ground
  • Mix and pour the concrete
  • Screed and level the slab
  • Trowel any edges
  • Allow it to dry and brush it

For a more in-depth explainer, check out the video below:

Paved Base

A more cost-effective alternative to a concrete slab would be to use pavers. Paving stones are a particularly good choice for a plastic shed base.

Simply level your site (like in step 1) and either assemble from your backyard or buy, some pavers. Dig out shallow footings at each corner of your site (and in the middle of each side of your shed to be on the safe side).

Using builder’s sand, fill the footings with compacted sand and sink the pavers into them. Check that they’re level across the whole site and then you can add a layer of soil over them.

Damp Proof Membrane

For a seriously solid ground base, you might want to consider installing a damp proof membrane.

This durable material (also known as a weed membrane) will not only protect your shed floor from water ingress but from weed growth. Damp-proof membranes can be sunk beneath concrete or gravel foundations like pea gravel.

Bases for Metal Sheds

Concrete slabs work particularly well for metal sheds as you can drill bolt holes into concrete. You can then position your shed and secure it to your slab.

Note: Whichever method you choose, we recommend that you have a 2” (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” to the overall base dimensions, to ensure an adequate base size for your shed.

Step 3: Build Your Shed Base

Now that you’ve settled on your shed base “based” on:

  • Your budget
  • Your needs
  • Your garden shape, size, runoff
  • The size and weight of your proposed garden building
  • Your available tools and expertise

You can start by digging out your shed foundation. Begin your ground preparation from raking to remove any weeds, leaves, or other hazards. This will help avoid future deterioration to your shed’s base, especially if you install a weed membrane.

Next, mark out your shed site with stakes and a string line. This is a highly achievable task even if you’re not a DIY enthusiast! Continue to rake and level the area inside the string line.

This step will be the same no matter which foundation kits you use. Keep scrolling to see the next steps for concrete vs timber base.

How to build an Eze shed base

Most of our garden sheds come with the option to purchase an Eze base. This is our recommended base for most sheds, due to its ease of installation.

The Eze Base is made up of a wooden floor surround, supported by wooden bearers which span the depth of the shed. It can be fixed into the soil or soft ground via sharp-ended wooden plinths, which are supplied with the base. Make sure that wherever you are planning to install it, the ground is level.

Watch the video below to see exactly how to install an Eze base:

How to build a concrete shed base

You will need:

  • Pegs and string
  • Building sand
  • Standard cement (all-in ballast, cement & water)
  • Timber boxing
  • Concrete screed
  • Hand trowel
  • Tape measure
  • Spade
  • Sweeping brush

To get your concrete perfectly level you could always hire a laser, but this requires some previous knowledge and may be expensive. Still, concrete is great for larger sheds.

1. Mark Out Your Base

…where you’ll be placing your garden shed. Make sure to plan for a 2m gap between the shed and any boundaries. Using pegs and string, mark out the base 2 inches (5 cm) larger than the area of the building on each side.

Remember to test the size by measuring the two diagonals to ensure the area is square.

2. Level off the Area

Concrete requires 3” (7.5 cm) of compacted hardcore (all-in ballast or other crushed rubble/gravel) underneath the 3″ 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” (15 cm), to allow for the hardcore layer and 3” (7.5 cm) of concrete. Level the area with a rake and spade and remove the pegs.

Ricky and Morty True Level

3. Level Your Hardcore

Set up your timber boxing. This involves measuring, cutting and fitting timber to the shape of the base in order to contain the concrete.

Check diagonal measurements to ensure your 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.

Man stood at cement mixer tipping it into wheelbarrow
Credit: Boel’s

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.

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. Use a sawing motion slowly 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 will be a smooth, solid and level base – the perfect foundation for the construction of a garden shed.

How to build a paving slab shed base

You will need:

  • 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 Out Your Base

…where you will be placing your garden shed. Make sure to plan for a 2m gap between the shed and any boundaries. Using pegs and string, mark out the base 2 inches (5 cm) larger than the area of the building on each side.

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” (7 cm) to accommodate the base. Level the area with a rake and remove the pegs and string.

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. Be sure it is level.

4. Lay the Paving Slabs

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.

dirty hand trowel on tiles
Credit: Unsplash

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-edged piece of timber to check if the base is level from each corner.

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.

Step 4: Shed Installation

Well done! You built your first shed base out of timber, pavers, concrete, or a gravel-filled Ecobase. Once you’ve allowed that to set if need be, you should be ready to start building your garden building onto it!

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 (unless you’re pouring a larger concrete slab). When it comes to actually assemble the shed, we do recommend an extra person is on hand for lifting and placing roof and wall panels in place.

Our BillyOh buildings come as pre-measured and cut panels from our expert craftsmen, ready for you to simply assemble. With just you and a friend and some basic tools, you can have even a 16x8 shed up in a matter of hours.

So revisit this guide to decide on which base suits you best. Once you’ve done that, check out our range of garden sheds via the button below!

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FAQ

1. Mark out your base with pegs and string line (with a 5cm overlap on each side)

2. Dig out, rake, and level the proposed area to a depth of approx. 7cm
3. Dig out pads for pavers at the four corners of your shed (and once more along each side)

4. Mix general purpose cement with sand and water and spread evenly in the pads approx. 4cm.
5. Sink pavers into these holes and level across the whole site

Concrete slabs: For metal sheds, heavier, and more permanent structures

Pavers: For a budget-friendly and easy DIY alternative

Timber sub-floor: For wooden sheds to raise them away from ground moisture

Ultimately, it will depend on your budget, shed type, and needs.

 

Mark out and level the proposed site of your shed. Build timber boxing (formwork) and raise/lower it to the desired height of your slab. Rake, level, and compact hardcore inside your timber boxing.

 

Mix and pour the cement and screed it as you go. Finish off any edges and corners with a hand trowel and allow to dry. Brush your slab to finish.

The easiest way to adjust the level of your shed base is to level the ground of your proposed site first. Start with a rough eye level using a rake or loam leveller and progress to using a spirit level. You can lay a level across, for example, pavers at opposite ends of your site or on top of timber boxing. If the distance is too great, run a string line between the two points to see where your site is low or high.

Absolutely. Building a shed directly on grass can lead to rising damp, weed ingress, rot, and even an unsafe structure. Building a shed on natural ground will be unlevel, causing uneven and undue stress on your shed which could shatter windows and warp doorframes. So not only do you need a shed base (timber sub-floor, pavers, concrete, gravel base), you also need a level base.