Shed Base: how to choose and build a foundation for your garden building

So, you've got a good idea of which bike shed you want. But before you bite the bullet and place an order, you need to think about your shed base. That is: the foundation that the garden building is going to sit on.

Why? Because it's really important! Thinking about the base may change where you finally put the shed in your garden. It may even change the size or type of building you buy.

And the truth is: in most cases you probably won't be able to get away without building some kind of base.

So let's deal with that first...

Do you really need a shed base?

Whichever type of shed you choose, it must be built on a level surface. If not, everything will be wonky!

The building will be difficult to put together because the different parts won't line up properly. And if you do manage to build it, the wonkiness puts a strain on the joints which will undermine the structural integrity and ultimately shorten the life of your shed.

A wonky shed won't last long

If you build your shed on an unlevel surface it won't last long

Plus, you'll probably struggle to open and close the door, which is really annoying. And if the shed's got windows, the irregular pressures on the frame (caused by the wonkiness), may cause them to shatter!

But why does that mean you need a shed base? Surely a level piece of ground would suffice?

Well, in some instances, yes. But often no. It will depend on the type of garden building you've chosen and what sort of ground you're talking about...

Can you put a shed directly onto your patio or driveway?

Yes. If you have a flat, hard (paved or concrete) surface, such as a patio or driveway, then you'll be able to place any kind of shed directly on top of it...

A wooden shed on a patio

Any shed can be put directly onto a level patio or driveway

It must be completely level though, or you'll have all the structural problems I mention above. But grass or dirt and even gravel are a different matter...

Can you put a wooden shed directly onto grass, dirt or gravel?

No. Wooden sheds are susceptible to water damage. So it's vital you keep them off the ground where they would get damp and start to rot, which would shorten the life of your shed massively.

QuickJack shed base

A shed base will keep your shed dry (QuickJack base)

Shed bases lift them away from the ground and the extended exposure to moisture that causes the problem.

Can you put a plastic shed directly onto grass, dirt or gravel?

Not really. Plastic sheds aren't susceptible to water damage themselves. But if the shed sits on wet ground, extra moisture will permeate the air inside, causing increased condensation which will damage your bike and other valuables.

A plastic shed directly on top of a lawn will suffer from extra condensation

If you plan to store heavy items in the shed, they may cause it to sink into the soft ground in places, making the building wonky and structurally unsound.

And how level is that patch of lawn, dirt or gravel anyway? Often these areas look much fatter than they actually are! Plastic sheds are probably the most susceptible to damage from unlevel surfaces.

Can you put a metal shed directly onto grass, dirt or gravel?

No. Many metal sheds don't come with floors, so that would obviously be a disaster! However, metal sheds are also heavy, so even when they have floors, you can't place them directly on a lawn as they're likely to sink in.

Metal shed with no floor

Metal shed with no floor are particularly unsuited to lawns, gravel and dirt!

Plus, if they sit on moist ground, even the most well galvanized metal sheds are likely to start rusting after a while. And you'll also get increased condensation issues which will corrode your bike components and other valuables!

What are the different types of shed base?

If you've got this far then you've probably accepted that you're going to have to put your shed on some kind of base! The question is what kind? Well, the good news is that they're loads of choice these days.

And they don't have to be a DIY nightmare to install!

There are 6 commonly used types of shed base. And I'll go over them all here, from the simplest to the most complicated...

  1. pressure treated wooden battens
  2. wooden frame
  3. plastic grid or runners
  4. paving slabs
  5. timber decking
  6. concrete

1. Pressure Treated Wooden Battens

This is a quick, easy and inexpensive option for wooden sheds. Simply place a series of wooden battens on the ground, so that they run perpendicular to the beams in the shed floor. They should be the same size (at least), as the shed and be spaced out so there's one every 2 ft (30 cm).

Wooden Battens

Wooden Battens : quick, easy, cheap (from Stix and Stones)

And then just put the shed on top of them!

The wooden battens must be pressure treated so they're protected from moisture and insect damage. And they must be completely level. So you'll need to prepare the ground that you put the battens on, so that it's flat.

Wooden battens will last for many years. And this is a "tool free" way to make a functional shed base. However, there could be a fair bit of movement as they settle, which could lead to structural issues in the shed over time.

Wooden battens are not suitable for plastic or metal sheds as these type of sheds don't have self supporting floors.

2. Pressure Treated Wooden Frames

A wooden frame makes a great base for a wooden shed on a lawn or softer dirt surface. It's essentially a bit of an upgrade to the wooden battens I talk about above. In fact you're basically just connecting the battens to make a more structurally sound grid.

Wooden frame shed base

With a wooden frame you don't need to level the ground!

But there is one fundamental difference between a wooden frame and every other type of shed base...

If you're going to use the shed base on a lawn, earth or other soft ground, you'll add legs to the wooden frame. And by hammering each leg into the ground to a different degree, you can create a level base (without needing to level the ground underneath it).

So, while with every other type of shed base, you need to level the ground you put the base on, with a wooden frame, as long as the ground is more or less flat, you can adjust the frame itself to provide a perfectly level base for the shed.

And this means much less work for you!

A wooden frame is also much stronger than a series of wooden battens. And because everything is connected, it's much less likely to "unlevel" itself in the same way battens might do and cause those structural problems in your building.

You could build your own frame. But every shed store I know also sells wooden shed base kits that are specifically designed for their sheds. The wooden beams won't need cutting and you'll get all the fixtures and fittings you need.

So I think it would be daft not go with one of them!

If you're going to put your shed on a hard paved or concrete surface, then you could use the same wooden frame but with adjustable metal feet. However on concrete and paved ground there are other good options too.

Also bear in mind, these wooden frames won't work with plastic and metal sheds as they don't have self supporting floors. However, if you fix an OSB or Plywood floor to the top of the frame, you can put any type of shed on top.

3. Plastic Shed Base Kits

Plastic shed bases are a newer development. But there's a a lot to like about them! First of all, they're modular and super light, so there's no lugging around great lengths of timber. And no drilling holes and screwing things together.

Plastic grid shed base kit

Grid based plastic shed base kit: suitable for all types of shed

In fact you won't need many tools at all. You'll usually get a number of different pieces that simply snap together like Lego!

They're free draining and self ventilating, so they do a really good job of keeping your shed floor dry. And they're made from 100% recycled plastic, so you don't have to worry too much about their environmental impact

Plastic bases can be fitted on all types of surfaces including concrete, paving slabs, gravel, lawn and dirt. But you must ensure the surface is level before you start and that can involve quite a lot of preparation.

Grids or Runners?

The plastic grid systems involves clicking together different tiles to create a plastic raft onto which you lay the shed. While with the plastic runner systems, you actually clip runners directly onto the beams of the wooden shed floor.

Plastic Runners Shed Base Kit from EcoBearer

With both systems you'll probably need to saw some of the bits of plastic so they fit your shed floor perfectly. But compared to other types of bases, they're relatively quick and pretty effortless to install.

And although they're most commonly used with wooden sheds, you can put any type of bike shed on a plastic grid shed base: wooden, plastic or metal (as long as it has a floor).

4. Paving Slabs

Paving slabs are the old school version of the modern plastic grids! And they'll certainly provide a more solid base and better security than plastic.

Metal shed on paving slabs

Paving slabs provide a solid and secure shed base

But they're also heavy to handle, require lots of ground preparation (if you're going to do it properly), and (if you don't do it properly), can be prone to some movement as they settle, which can unlevel the shed.

If you're going to install a paving slab shed base on a lawn, dirt or gravel, you must ensure the ground is completely level and to reduce the chances of uneven sinking, you should really lay a sub base of hardcore first (although for a small shed, and most bike sheds are quite small), you might be able to get away without this step.

So a paving slab shed base can be quite a lot of heavy work. But on the plus side, if you're building a metal shed, you'll be able to bolt the shed (and a ground anchor if necessary), to the paving slabs for extra security.

Since they provide a super stable and strong foundation, paving slab shed bases are suitable for all types of shed: wooden, plastic and metal.

5. Timber Decking

Timber decking seems to to get more popular every year. And if it's strong enough, it can provide a suitable base for a garden shed. Most bike sheds are small and light enough to be OK in this respect.

Wodden shed on timber decking

Timber decking makes a good base for a shed

You need to leave plenty of room around the edges for installation and maintenance. And bear in mind that the decking will be raised off the ground, so navigating that step with a heavy bike or lawnmower may not be ideal.

Installing timber decking isn't a small job. However, if you're already planning on installing decking for other reasons, incorporating a shed may make sense. And it's a surface that's suitable for all types of shed: wooden, plastic and metal.

6. Concrete

Concrete bases provide the strongest and most durable foundations for a shed. However they're also the most expensive and the most labour intensive to install. And it's hard, heavy and dirty labour!

Laying a concrete shed base

Laying a concrete shed base is hard work!

They require the extra step of laying a hardcore sub base. And you need to build a frame to contain the wet concrete. Mixing concrete by hand is strenuous. And if you decide to use a concrete mixer instead, you'll have to go through the cost and hassle of hiring one.

Concrete is incredibly environmentally unfriendly. Much more so than any other option. And bear in mind that unlike the other options, a concrete base is a permanent addition to your garden. If you move the shed, that big slab of concrete can't be moved with it.

So they're definitely not suitable for renters. Or anyone else that doesn't want to make a permanent change to their garden. In fact, the extra work involved, the permanency of the installation and the environmental issues, mean I would only recommend new concrete bases where they're absolutely necessary.

So that would be for really big sheds, garden buildings and log cabins which require very solid foundations. Or for people with a metal shed that requires the maximum security when the shed in anchored to the base.

Here's a good video that shows the amount of work that's involved in laying a concrete shed base...

Concrete bases are suitable for all types of shed. But unless you're installing a super heavy garden building or you absolutely must have that bit of extra security that a shed bolted into a concrete base provides, I'd recommend going with another option.

What's the best base for a wooden shed and how do you install it?

If you're going to put the shed on a softer surface, such as a lawn or earth, then a "wooden frame shed base kit", with foot spikes to anchor it into the ground is usually the best choice for small to medium size wooden sheds.

You won't have to worry about levelling the ground first, which is a massive bonus. And if you can put large Ikea furniture together, you'll have no problem putting the wooden frame together!

I really like Power wooden bike sheds and they sell a wooden frame shed base kit that's perfectly sized for their sheds. However they all work the same way, so you can get a good idea of how to put one together from their video...

If the ground is uneven, but too hard for spikes, then you can get wooden frames with metal feet that rest on top of the ground. These can often be adjusted (up or down), even after the sheds on top of the base.

If you're laying the shed on a hard, level surface such as a patio or driveway, then although you might be able to get away with placing the shed directly on the ground, I highly recommend the plastic runners which will clip onto the floor beams of the shed...

They're pretty cheap, super easy to install and will keep the wood off the floor and away from any kind moisture that will shorten the lifespan of your shed.

Most wooden sheds are available with matching wooden frame bases that are the perfect size for that particular shed, which also saves you a lot of hassle.

What's the best base for a plastic shed and how do you install it?

If the ground is uneven, a "wooden frame shed base", with foot spikes or metal feet will enable you to create a level platform for the shed, without needing to go through the difficult process of levelling the ground below.

You can't put a plastic shed directly onto the beams of a wooden frame though. The floor of the plastic shed isn't strong enough. So you'll need to fix a piece of OSB3 or Plywood on top of the wooden frame to act as a solid floor for the shed to sit on.

Here's a video that shows you how to make another wooden frame base, again using a kit. At the end it shows the sort of platform you'll need to add before you can put a plastic shed on top.

The problem with a kit is that you might not be able to get one that's exactly the right size for your plastic shed (so you'd have to buy a slightly bigger one, creating an edge). And you'll have to sort out a plywood floor yourself.

So instead of kit, to get a perfect size, you could just build the whole thing yourself from scratch. 

If this sounds like to much DIY nonsense, then an easy alternative is a plastic shed base kit. The grid system base kits are probably best for a plastic shed. But you'll need to properly level out the ground first.

This will involve marking out the area, lifting any turf, digging down a little and then adding a layer of sand or pea gravel to create a level surface, if it's not already been levelled by your digging.

Then it's just a case of laying out the waterproof membrane that comes with the shed base kit, clipping the plastic tiles together and filling some (or all) of the cells in the tiles with pea gravel. And putting the built shed on top.

Here's a video that gives you a basic idea of what you'll need to do to install a plastic shed base kit...

Whatever base you go for, don't forget to anchor the shed to the ground. Plastic sheds are so light they can get blown over in heavy winds. With a wooden base that would involve bolting it onto the OSB or Plywood floor. With a plastic base, you would need to stake it into the ground.

What's the best base for a metal shed and how do you install it?

A paving slab base is the best choice for most smaller and medium size metal sheds. Compared to concrete, it's much easier to install, it can be uninstalled if you change your mind, and is much more environmentally friendly.

Add it will provide better strength and security than a wooden or plastic base as you'll be able to bolt both the shed and a ground anchor into the paving slabs for extra security. 

Here's a great video that shows you how to lay a paving slab shed base properly...

Plastic vs Wooden vs Paving Slab Shed Bases

All three can provide a stable, solid, moisture free foundation for your garden shed. But they all involve some manual work. And which one you choose may depend on what kind of tools you've got and what kind of work you're most comfortable with.

For plastic and paving slab bases the real work is in levelling the ground. While with wooden bases it's putting the frame together where the labour is. Once you're clear on what you'll need to do in the area you've chosen to put your shed, it should be a relatively easy choice.


More Good Stuff:

DIY Bike Shed

How to make a DIY bike shed

Win a Bike!

Win a Bike!

Bike sheds

How to choose a bike shed

Last Updated on April 24, 2021 by Carl Ellis

Carl Ellis
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