Any good shed starts with a solid and level base that makes up the foundations. Using new or existing paving slabs could create the perfect solution.
Nearly every garden has a shed these days, and the popularity of outbuildings seems to be increasing every year. A shed creates the perfect location to store garden tools and furniture, keeping them dry and secure. Larger sheds can even be used as a workshop or converted to a man cave to create the perfect escape in the garden.
Sheds last for a long time, and with the correct maintenance are often in position for over 15 years. When it’s time for a replacement, we recommend investing in a high-quality building and ensuring a suitable base is constructed.
The base of a shed makes up the foundations that everything else will sit on top of. With lots of items stored inside, the shed can weigh hundreds of kilograms. All of that weight is relying on the base underneath to remain securely in position. A poorly constructed shed base can lead to strain on the wood and gaps appearing in the structure.
Some advice we give to anyone constructing a garden building is to ensure the base is both solid and level. A solid base will not move in the future when there is lots of weight sitting on top. A level base is just as important to ensure the shed joins together correctly. Garden buildings are manufactured to tight tolerances and an uneven base can lead to challenges such as doors that don’t open easily when the panels are assembled together.
With lots of different options available to use as a shed base, we often get asked whether paving slabs make a good solution. Let’s take a look at our top tips for using slabs as a shed base.
Can I put a shed on paving slabs?
It’s possible, yes, to put a shed on a base constructed from paving slabs. The shed should sit on top of pressure treated bearers to allow airflow underneath the building.
Paving slabs are one of the most popular choices when it comes to choosing a shed base. When installed correctly, the construction is solid and not going to move with the weight of a shed on top. Each slab can easily be levelled to create an even foundation across the length and width of the shed. Be sure to choose smooth paving slabs and avoid any with patterns that may create an uneven surface. We don’t want water puddling on uneven parts of the slabs.
When using a paving slab base, it’s important to use pressure treated bearers that sit between the shed and the base underneath. The bearers are long planks of wood that support the full weight of the shed. Some sheds come with optional bearers, but often they will need to be purchased separately.
The purpose of using wooden bearers is to allow airflow underneath the shed. This stops the timber floor from sitting in puddles of water that can begin to soak through and into the building during the winter months. A constant flow of fresh air also stops moisture levels from building up, to prevent the growth of the damp and rot in the timber.
Wooden bearers come pressure treated. We also recommend applying an additional wood treatment to create an extra layer of weatherproofing. Pay close attention to the ends of the wood to reduce the chance of moisture soaking in over time.
To further avoid water puddling on paving slabs, you may choose to use gutting where rainwater runs off the shed. We recommend not using paving slabs near large trees or pushes, as the roots could begin to cause movement in the slabs, leading to an uneven surface after a few years.
Can I use existing paving slabs?
One of the reasons paving slabs bases are so popular, is because many of us already have a paved area in our garden. A low-cost option to avoid constructing a new shed base is to use an existing paving slab patio.
It’s fine to use existing paving slabs, but we need to make sure they are both solid and level first. On older patios, the mortar can sometimes break away, leading to movement in the slabs. Be sure to check each paving slab to ensure it’s still solid. Any loose slabs can be secured back into position with new mortar.
When paving slabs are installed as a patio, they are often fitted on a slightly uneven angle. This design is to allow rainwater to run off easily. However, this is not suitable for a shed base as we need the foundation to be completely level. Use a spirit level to check if the slabs are even or whether they will need to be adjusted.
How to construct a paving slab base
A paving slab shed base can be completed by professionals or as a DIY job. Once a suitable location has been found, the ground is dug out to a depth of around 120mm. We dig this deep to fit a sub-base of hardcore before the paving slabs are installed.
With the sub-base installed and compacted, the paving slabs are installed on top. Each slab sits on mortar that will hold the slabs securely into position once dry. A mallet is used to tab the slabs into place and a spirit level is constantly used to ensure each slab is level.
Once the paving slab base has been constructed, we recommend allowing at least several days for the mortar to dry completely. The shed can be very heavy and the last thing we want is the foundations moving during installation.
Finding the best location
Be sure to find a suitable location to install the shed base, once it’s installed, a shed is difficult to move. The base is constructed several centimetres larger on each side of the shed, so we need to make sure there is adequate space available.
If the garden is on a slope, we recommend installing the shed near the top. During heavy rainfall, the water can often puddle at the bottom of the slope. Gardens that have a large slope may find that ground screws are a better solution for creating a shed base.
Leaving a gap for access around every side of the shed is a good idea. As well as making installation easier, it also allows for maintenance in the future. The exterior wood treatment on a shed may need reapplying after several years. Enough room on each side makes it easy to maintain.
A paving slab base is just one option when it comes to creating a suitable shed foundation. There are plenty of alternative options depending on the budget available and the location where the shed is going to be installed.
If the garden is on a slope and installing slabs or concrete is not an option, ground screws are a smart solution. Each ground screw is essentially a large screw that goes directly into the soil. As they are raised above the ground, airflow is maintained underneath the shed.
A benefit of using ground screws is that they can be installed at the same time as the shed and weighted immediately. No need to wait around for the base to dry. A timber frame for the shed is used and attached directly to the ground screws.
A concrete base is often our first recommendation when it comes to the best foundations for a garden building. Poured concrete is easy to get level and once dried creates an extremely solid construction. Just like using paving slabs, a sub-base is first installed and compacted. The concrete is then poured on top and a tampering board is used to smooth and level the surface.
Concrete bases can take a long time to dry and we recommend waiting at least several weeks before installing a shed on top. A damp proof membrane can be installed inside the base to prevent moisture from rising from the ground underneath.
Overall, it’s possible to put a shed on paving slabs. Any garden building requires a foundation that’s both solid and level, which can be achieved with paving slabs. If the garden already has a patio made from slabs, they may be suitable without the need to install a separate base.
When using paving slabs, be sure to install pressure-treated wooden bearers between the shed and the base. The bearers are essential to allow airflow and keep the floor of the shed dry.