How to Build a Shed Base
Introduction to building a shed base
When constructing a garden shed, summer house, workshop or other garden building, it is imperative that you provide a firm and level base. If your shed base is not level, or subsides over time, then the structural integrity of your garden building will suffer, and you may find joist splitting, panels breaking, and doors and windows sticking.
Building a shed base needn’t be an overwhelming chore, and can be completed by one person. Read on for our handy guide to building a shed base using various materials.
Where Should I Build a Base for my Shed?
First things first, you need to site your garden building in the optimum place in your garden. You’ll need to consider things such as:
- Access for assembling your shed. If you have chosen the home installation option, then we require a gap of 2’ around the building in order to construct it
- Access around the building for applying and wood treatment and re-applying it when necessary
- Surrounding greenery, such as overhanging trees or young saplings that may grow
- Panoramic view from your shed or summer house, and the amount of natural light your shed will receive. This is especially important for summer houses and workshops, where you are more likely to spend more time in your garden building, rather than in a storage shed
- Distance from your house, which may need to be taken into consideration due to your local building regulations, or if you intend to install electricity in your shed, summer house or workshop
Types of Suitable Base for a Shed
There are a few options when considering which base to build for your shed, each with their own advantages and disadvantages. We recommend one of the following four shed bases:
Probably the most time consuming and labour intensive option, yet if done correctly, your concrete shed base should outlast even your shed!
This option is a little quicker and cheaper than building a concrete base for your shed, but laying slabs level can be a tricky process if you have never done it before.
A simple, easy to prepare permeable membrane base. Lay out, fill with gravel, and build your shed!
A pressure-treated wooden base specifically designed to house wooden garden buildings up to 10’ x 8’. Read our Walton’s Portabase Guide for more information and instructions on use.
Building a Log Cabin Base
If you are building your own log cabin, then please see our How to Build a Log Cabin page for details on building a base.
Concrete Base
Tools Required:
- Pegs and string
- Sand and gravel mix
- Hardcore
- Standard cement
- Timber for base formwork
- Tape measure
- Spade
- Sweeping brush
- Cement mixer
- Spot – mixing board
- Wheel barrow
- Tamp board
- Spirit level.
For full instructions on how to build a concrete base for your garden building please see the below video for an easy step by step guide.
Step 1:
Be sure to position your garden building in an optimal space, allowing enough distance from hedges or fences for easy access to all sides. Using pegs and string to mark out the base the same area as the building's floor. Finally, measure diagonals to ensure the area is square.
Step 2:
A concrete base requires 3 inch (7.5 cm) of compacted hardcore underneath the 3 inch (7.5 cm) concrete layer. The base can be level with the ground or raised above it. If it is to be level excavate the top earth to 6 inch (15 cm) to allow for the hardcore layer and 3 inch (7.5 cm) thickness of concrete. Level the area with a rake and spade and remove the pegs.
Step 3:
Set up levelled formwork. This involves measuring, cutting and fitting timber, to the shape of the base in order to contain the concrete (as shown in the diagram). Check diagonals to ensure the formwork is square. And also ensure the formwork is level, as this will determine whether your base is 100% level. Next, spread a layer of well compacted hardcore and cover with a liberal amount of sand.
Step 4:
Next, mix concrete using one part cement to five parts ballast or use bags of dry-mixed concrete to which you just add water. Small amounts of water should be added at a time and mixed into the concrete mix to ensure excessive amounts are not added making the cement sloppy, as the concrete should be kept on the dry side.
Spread the concrete evenly and slightly proud of the formwork. This can be then levelled off with a long straight edge of timber resting on the formwork using a sawing motion slowly (as shown below) 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 is a smooth, sound, level base - the perfect foundation for the construction of a garden building or one of our wooden sheds. Allow 48 hours for the concrete to set prior to assembling your building.
Slab Base
Tools Required:
- Pegs and string
- Flat Face Paving Slabs
- Sharp sand
- Standard cement, rake
- Tape measure
- Spade
- Rubber mallet
- Sweeping brush
- Spirit level
Step 1:
As mentioned above, decide where to position the shed in an optimal space. Allow enough distance from hedges or fences for easy access to all sides. Using pegs and string to mark out the base the same area as the building's floor. Finally, measure the diagonals to ensure the area is square.
Step 2:
Strip the topsoil and dig out to a depth of approx. 2.5 inch (7 cm) to accommodate the base. Level the area and remove the pegs.
Step 3:
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. Now, rake this to a level.
Step 4:
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.
Step 5:
The completed base should now be level and square. Do one final check with a long straight edge to check if the base is level from each corner, and also measure the diagonals to finally check the base is square. Brush off any excess dry sand/cement mix, which could hinder the leveling of the shed. The result is a smooth, sound, level base - the perfect foundation for the construction of a garden building.
Tanalised Bearers Base
Tools Required:
- Pegs and string
- Tape measure
- Spade
- Rubber mallet
- Spirit level
- Hardcore (crushed lime stone)
- 75mm x 75mm Tanalised Bearers
Step 1:
As mentioned above, decide where to position the shed in an optimal space. Allow enough distance from hedges or fences for easy access to all sides. Using pegs and string to mark out the base the same area as the building's floor. Finally, measure the diagonals to ensure the area is square.
Step 2:
Strip the topsoil and dig out to a depth of approx. 3 inch (7.5 cm) to accommodate the base. Level the area and remove the pegs.
Step 3:
Fill the trench with hardcore and compact down as level as possible.
Step 4:
Lay the bearers on the hardcore, 16 inches (40cm) apart. The bearers should be laid at 90 degrees to the building's floor joists, i.e. if the floor joists run from side to side of the building then the bearers will need to run the length of the building. Check the orientation of the floor joists on your building as they do vary from building to building. Using the spirit level and rubber hammer, tap the bearers into the hardcore until they are perfectly level.
How to Build an EcoBase
Step 1:
Clear the area you’re going to use ensuring the ground is flat and there’s a slightly larger area needed than you require.
Step 2:
Cut the permeable membrane to size and lay flat.
Step 3:
Lay and interlock the grids and secure with 6 ecopins per grid spaced in alternate lugs. Take care to make sure that the feet of the grids are facing downwards and that there are no gaps between grids.
Step 4:
Cut the grids to the same size as the shed using a handsaw or alternatively, leave the EcoBase larger than the garden shed and fill with gravel. This will help to keep the timbers of the garden shed dry and free from splash back.
Step 5:
You are now ready to construct your garden shed, summerhouse or greenhouse onto the EcoBase.
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