How to Build a Base for your Garden Building

Published: 12/04/2019

Everything needs a solid foundation. Whether that's a business, a relationship or your garden building! A suitably durable, perfectly level base is the first step to giving your building the longest possible life. Incorrectly install your base and you risk facing serious problems down the line. Not only is the material of the base important, its placement is too.

Where do I build my base?

You should consider the following factors when choosing the location of your base.

1. Walls and fences. You should not build your base too close to any walls or fences, as this could cause splashback onto your building during rain. Also, a roof overhang could lead to your building running water into your neighbour's property. Make sure you leave sufficient space around your building to be able to effectively treat and paint the exterior.
2. Trees and bushes. Overhanging branches can potentially scratch and damage the felt in your shed or drip water onto your building. Also, be mindful of the potential for falling leaves. Buildup of foliage and other debris can damage your building.
3. Ease of access. If you plan on carrying bulky items in and out of your garden building, it would make sense to install your base close to a path. If not a path, at least make sure the location of your building is an easy route from your house. Take into account the space that will be required for doors or windows to fully open. Also, wiring or plumbing your building will be a lot easier if it is located next to an electricity or water supply.
4. Views! If you'll be using your building as a place to relax or entertain, it's better to have a view of your well-landscaped garden or new water feature instead of your wheelie bins. Even if you don't have the world's best view, it'd be good to position your shed or cabin somewhere which will allow natural light into the windows.

Note: The area you choose to build your base must be level - so it's best to choose an area that's as flat as possible. If you have no choice but to place it on a slope, take a look at our post on how to build a shed base on uneven ground. Now that you know where to build your shed base, the next thing to consider is how to build your base. There are 3 methods which all result in a suitably durable base, so the choice of material is yours. It is important to build your base slightly larger than the exterior dimensions of your building - approximately 30-40mm each side.

Prepare the area

1. Clear the area so it is free of any vegetation or debris.
2. Using pegs and string, mark out the chosen area for your base. Measure diagonally to make sure your base is square. If your base is perfectly square, these measurements will be equal.
   

Concrete base method

We would recommend a concrete base for larger buildings.

1. Use your pegs as a guide to excavate the area to around 6” (150mm) deep.
2. Lay approximately 3” (75mm) of firmly compacted hardcore, scalping or brick rubble as a sound foundation and level with compacted sand, if appropriate. A rake can help make sure the area is level. You can now take down the pegs and string.
3. Use timber rails or steel shuttering to support the edges of your base. Ensure this is square and level by using a tape measure, spirit level and tri-square.
4. Lay approximately 3” (75mm) of concrete. You can either use dry mixed concrete, adding small volumes of water at a time, or use an 'all-in' ballast, cement and water mixture. Ensure that the mixture is not too wet, as this will weaken the concrete.
5. Evenly spread the concrete in the shuttering, making sure it is pushed into the corners and edges. Layer by layer until the concrete is flush with the framework is an effective method. Smooth the top using a float.
6. Cover the concrete with sheets to dry. If the weather is overly warm or dry, the concrete could dry out to quickly. To prevent this, spray it with water occasionally.
7. Once firm and dry the base is now ready for you to begin assembly of your garden building.

For more detailed information on this method, check out our comprehensive guide on how to build a concrete shed base. 

 Paving slab method

1. Use your pegs as a guide to excavate the area to around 2.5" (63.5mm) deep. Take down the pegs and string
2. Lay approximately 1.5" (40mm) mix of one part cement to eight parts building sand to create a dry sand and cement mix. Use a rake and spirit level to ensure the surface is level.
3. Begin to lay the paving slabs, tapping down with a rubber mallet. You should start from the corner, and ensure the slabs are slightly higher than the ground for easier water drainage. Check that the slabs are square and level by using a spirit level.
4. Brush off any excess sand and cement mix - the base is now ready for you to begin assembly of your garden building.

Timber bearers method

The first question for this method is how many bearers you will need. This will vary based on the size of your shed. Most of our Tiger Sheds come complete with bearers attached under the floor which run the length of the building. However, bearers on 10x8 and 12x8 buildings with 28x44mm framing run the width. Here are some examples for the minimum bearer requirements:

• 6x4 garden building – at least 4 bearers at 1150mm (4ft) long
• 7x5 garden building – at least 4 bearers at 1450mm (5ft) long
• 8x6 garden building – at least 5 bearers at 1750mm (6ft) long

1. Use your pegs as a guide to excavate the area to around 2" (50mm) deep. Take down the pegs and string.
2. Lay approximately 1.5" (40mm) gravel or soil. Use a rake and spirit level to ensure the surface is level.
3. Lay the bearers across the gravel/soil at equally spaced, 400-600mm intervals. Make sure they will be laid perpendicular to the joists your garden building will come with. You can use pressure-treated timber bearers or concrete floor bearers.
4. Use a spirit level to ensure that the bearers are level. You can tap them down with a rubber mallet if needed. 

Now you know the three methods of building a base, you can get started! If you have read this guide and feel that it would be too difficult, you should consult a local handyman to get the job done - it's important that the base is built properly. Want more detailed information? Consult our full Build a Base Guide.