Are you thinking of getting a garden room in your backyard? Garden rooms are extremely versatile and can be used in a variety of situations. Getting one is also fairly simple. All you have to do is choose one from a provider and there you go. 

The tricky part comes in when you need to prepare the foundation for a garden room. Some suppliers offer to do this for you, but if they don’t, you’ll have to prepare the foundation yourself. 

If you have no idea how to do this, keep reading.


How To Prepare A Foundation For Your Garden Room

Before you can build a foundation, you will first need to decide on the kind of foundation you want to use. Here are a few options:

  • ● Concrete slab
  • ● Plinth
  • ● Ground screws
  • ● Concrete pile


Now you might be wondering why there are different options for foundations. The different options are used in different sites. Here’s how your site influences which foundation you use. 

Unlevel sites will require a different strategy from level sites. You will also need to take into account the type of soil in your garden. If you choose the wrong foundation, you might end up with your garden room sinking into the ground, or worse breaking!

To avoid these problems, try following these steps or just hire a professional to do it for you.

Choose A Location For Your Garden Room 

One of the most important things you can do is choose a location while planning your dream garden room. If you can find a flat area in your backyard, it would be ideal, but plans can be made for slopes. It’s usually best to get experts out to assess the soil and other factors of your chosen site. They should be able to tell you which system will work best for your garden house. 

The most important thing for garden rooms to last is to have them on clear, flat foundations that aren’t prone to flooding. In some cases, the providers will recommend a foundation purely based on what you’ve told them. This may lead to complications and delays as unforeseen problems arise. It’s always best to get a professional out there to inspect the ground. 

Summer House Play Room

Laying The Foundation 

It's usually best to get a professional to do this part for you as well. The foundation is the most important part of your garden room after all. If you don't have a solid foundation, your garden room most likely won’t last very long. 

If you can’t find a professional and have to do it yourself, try following the steps below. 

Concrete Slabs:

To lay concrete foundations, make sure you level the area completely. You will need to clear all vegetation and rocks to make a nice flat area. Excavate the area and fill the excavated site with broken pieces of concrete, brick and stone. Keep in mind that the base or foundation you’re making should be at least 50 mm larger than your garden room base. 

The next step is to build a wooden frame around the edge of the excavated site. Once done, lay down a damp proof membrane to help with insolation and pour the concrete. Leave it to set for a few days. 

If you have a very big garden room, you might need to reinforce the foundation with steel rods. It’s best to have a professional install the foundation to make sure it's level.

If there are any trees near the foundation, it might not be the best thing to use a concrete slab. These may kill trees growing near or get damaged by invasive roots. 


The plinth is very easy to install garden room foundation. Due to not requiring any setting time, they are also the most popular choice. A plinth helps to distribute the weight of the garden room evenly which means no damage to the structure. 

These foundations are especially good at withstanding a large amount of pressure and movement. This means your garden room won’t get damaged if the round shifts for any reason.

If you're looking for an eco-friendly option, then you also might want to consider a plinth. They are just as easy to remove as they are to install and usually won’t leave a trace. 

Concrete Pile

Concrete piles use a combination of plinths and concrete slabs to create a foundation for your garden room. This foundation also usually use a steel structure that is driven deep into the ground to make the base sturdy. How deep it goes will depend on the type of ground conditions as well as what type of structure will be placed on top of it. 

These structures are highly water-resistant which means they won’t change form underground no matter how wet it gets. This makes them suitable for very large garden rooms. They are quite costly to install, however, due to their weight and the need for special equipment. 

Ground Screws

Using ground screws is a very new technique that makes setting a foundation so much easier. It is also a lot less invasive since you don’t need to dig up your garden or lay down concrete. They need to be installed professionally to make sure they are secure enough to support the weight of your garden room. A wooden platform can then be built on top to act as a base for your outdoor paradise. 

This method isn’t suitable for gardens with very loose soils. They are however the foundation of choice if you have uneven ground in your garden. 

Unsuitable Foundations

You might want to cut a few corners since foundations are quite expensive to install. I would advise against this. There are many ways to create an unsuitable foundation, but only a few right ways to do it. Unsuitable foundations include those that are:

  • ● Uneven
  • ● Too small
  • ● Made of a material that will rot away
  • ● Not deep enough
  • ● Not isolated properly
  • ● Not properly reinforced 


Are Foundation

Are Foundation Costs Included In The Cost Of Your Garden Room?

This is a question you should direct to the company you buy from. Some providers will set up their own foundations for their garden rooms. These will most likely be included in the initial cost. Others might expect you to set up your own foundation before bringing the garden room you ordered and installing it. 

Garden rooms that come with foundations are usually a bit more expensive than those that don’t. Installing your own foundation or asking a professional to come and do it, however, can be even more pricy especially if you do it yourself and something goes wrong. 

The best course of action is to find a supplier that will do everything from scratch. That includes laying the foundation as well as installing the garden room. 

If you’re comparing garden rooms, you might notice a significant price difference between garden rooms with foundations and those that come without. That is because foundation material is extremely expensive and more than likely the most important part of the whole structure so you cant just wing it. 


Now that you know a bit more about foundations, it’s time to decide what you want to do. I suggest getting a professional out of your home to give you the best advice. Once done you can either have the garden room company create a foundation for you or hire said professional to do it for you. I would not advise doing it on your own since so much can go wrong. Garden rooms are not cheap so you might as well do it properly.


How Deep Should A Foundation Be?

The foundation hole should be dug out around 150mm deep (6 inches). 75 mm (3 inches) of the hole should be filled with compacted hardcore (broken pieces of concrete, brick and stone) and 75 mm should be filled up with concrete. This creates a nice solid base for your garden room to rest on.  

What’s The Best Base For A Garden Room?

The best base for a garden room is a concrete slab. These are very sturdy, long-lasting and can be used in a variety of ground conditions. This type of foundation is quite invasive so might not be your first choice. 

How Thick Should A Foundation Slab Be For A garden Room?

The perfect thickness for a foundation slab is between 100-150 mm (4-6inches). This allows the structure to be sturdy enough to support the garden room on top of it. It also prevents the slab from breaking under pressure. Keep in mind that this depth might vary depending on the ground conditions in your garden.