The base of a shed is the foundation that will keep the building in place for years to come. Use a solid base to increase longevity and protect against damage.
A shed is essential in most gardens these days as a valuable location to store tools and garden furniture. If you are installing a first shed or replacing an existing one, it’s important to get the base correct first. An unsuitable base could lead to issues with a shed within a few years, as the building begins to wear & age over time.
Once the shed is constructed, it will be reliant on a stable base underneath to keep the building in position and protect against damage. Even small sheds can weigh hundreds of kilograms with equipment stored inside, so it’s important to plan the base properly.
All garden buildings including sheds, cabins and summerhouses need a good quality foundation. The base must be level and solid to provide enough support. A level base ensures all of the panels can connect together correctly during construction. A solid base prevents movement or subsidence over time, which can put stress on the structure of the shed walls.
A common question we get asked is to recommend a shed base that’s easy and quick to install. Let’s take a look at whether a grass lawn is suitable and the alternatives we recommend.
Can I put a shed on grass?
We would not recommend using a grass base for a shed and instead choose a solid foundation such as concrete or paving slabs.
There’s a number of challenges with trying to install a shed on a grass lawn. Even though it is possible to level out grass, it’s likely to quickly become uneven again once the weight of the shed is placed on top. A grass base also goes against the principle of using a solid base for any garden building.
The result is likely going to be movement underneath the shed that will lead to sinking in the corners or extra strain on the structure, particularly if storing heavy equipment. During rainfall, the saturated ground will be moulded where heavier items are placed. When wood is warped in an uneven shed due to movement, the doors and windows can become difficult to open and gaps may appear where the panels are joined together.
With damage to the structure, the shed is vulnerable to water leaks and further damage as it begins to deteriorate. The equipment stored inside is then exposed and the shed will eventually need replacing.
Moisture is another significant challenge when placing a shed on a grass lawn. During heavy rainfall, water can puddle and sit around the base of a garden building. As the shed is not raised, the floor will be sitting in water that can quickly saturate through the wood. With no ventilation and constant damp, the result will likely be mould growth starting at the bottom of the shed.
But I still want to use a grass base?
A grass base is far from ideal for a shed, but if you still go ahead, be sure to take additional steps in preparation first. The grass lawn should be completely even and compacted as much as possible to reduce movement once placed on top.
A plastic shed base should be installed on top of the grass and then the shed can be constructed on top. The plastic base is a continuous and interlocking honeycomb structure sitting between the shed and the grass. By spreading the weight across the surface, any movement in the ground below is reduced and the shed is kept in position.
Using a plastic base to raise the shed above the surrounding ground also prevents moisture issues. The shed floor is lifted above any puddling water and the plastic against the floor will not absorb water or remain damp. The honeycomb design also allows ventilation and airflow underneath the shed to prevent rot in the timber.
As an additional step, consider using a vapour barrier attached underneath the plastic base. A vapour barrier completely blocks rising moisture from the ground below, preventing it from getting into the floor.
Can I put a shed on loose gravel?
A gravel shed base can be built, but the shed should not be placed onto loose gravel that is sitting in a garden. The reasons are similar to a grass lawn as loose gravel will not be solid enough to support the weight of a shed.
A gravel base can be constructed for a shed and will use wooden beams around the edges to keep the gravel firmly in position. A vapour barrier will also be installed at ground level to prevent moisture from rising. Once the gravel has been poured into the base, it will be compacted so that it is locked into place and not going to move once the shed is installed.
A plastic shed base can also be used with gravel. The gravel is filled in between the honeycomb plastic structure to increase strength without causing damp.
Alternative shed bases
A solid and level base is essential for the long-term structure of a shed. There are plenty of great options available, even if a low-cost or fast solution is required.
Our recommendation is to use a concrete base whenever possible for a shed. This creates a very strong foundation that is suitable for storing heavy tools and garden equipment. The concrete can also be levelled at the time of installation to ensure evenness throughout. Raising the concrete base above the surrounding groundworks prevents water puddling during the winter.
A concrete slab base can be inexpensive if constructed as a DIY task and completed over a weekend. Once the area has been dug out, a sub-base of type 1 hardcore is first compacted into the ground. Wooden shuttering is used to create an outline of the base where the concrete can be filled. With the concrete-filled, a tampering board is used to create an even surface to place a shed on top.
Installation of a concrete base should be completed several weeks before the shed will be installed as it needs type to dry out completely. A vapour barrier can be placed inside the concrete base just above the height of the surrounding ground. This will prevent moisture from rising from the ground underneath and affecting the shed floor.
Paving & patio slabs
If the garden already has a patio area, a low-cost option is to leverage the existing patio to place a shed on top. If the existing patio is being used, be sure to check its completely level, as many will not be to allow rainwater runoff. Installing new paving slabs can also cost less than a concrete base and the slabs can be picked up from a local garden centre.
Just like a concrete base, paving slabs require a sub-base constructed from type 1 hardcore compacted into the ground. The paving slabs should be a flat and smooth type without any patterns or unevenness.
To lay the paving slabs, a mix of mortar is used underneath and the slabs can be tapped into place using a mallet. As the slabs are installed with a small gap in between, rainwater is prevented from building up around the shed.
If a large part of the garden is being renovated, timber decking can transform the space around the shed. Decking looks great throughout the year and provides a sturdy base for a small shed to be installed on.
Installing timber decking can take time, and only makes sense for a shed if it is being installed in the garden anyway. The decking does require maintenance to keep it looking at its best, usually once a year. A wood treatment will be required to protect the timber from water damage and keep the colour looking good.
Decking is raised, so air can circulate underneath the shed and allow for good airflow. This protects the floor and prevents water from sitting at the bottom of the shed.
Overall, we don’t recommend using a grass lawn to install a shed on. While it may sound like a fast solution, it’s likely going to cause damage to the building within a few years. Any garden building requires a base that is both even and solid. Grass can move with the weight of the shed, particularly when it’s been raining, resulting in subsidence causing the timber to warp.
Instead, invest in a stable base that will maintain the longevity of the shed for years into the future. Concrete is our recommended choice.