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Base Requirements

Base Requirements

We cannot stress enough the importance of putting your Andover Garden Building onto a solid level foundation. Get it right and your building will fit together perfectly and last for years. Get it wrong and you could have problems with assembly, the shed will not last nearly as long and the doors may not close properly.

Positioning of your Building

The size of your building is approximate and does not allow for roof overhangs. When deciding where to site your building you must allow sufficient room for the roof and allow access for assembling, maintenance and retreating of the building. The minimum space required is usually 300mm (12 inch,s) (1ft) all the way around the building although 450mm (18 inch,s) is preferable. Your base does not have to be larger than the building.

If you are supplying your own bearers/ sleepers please check quantity and size of bearers required for your building. Larger floors are often supplied in two or more sections and need to be supported at the joins. Bearers to be at 90 degrees to floor joists - floor joists do vary depending on model and size of building.

We recommend a fully paved area

If using bearers or sleepers they must run the opposite way to the joists on the building floor.Direction of floor joists will vary depending on the size and model of the building. If using slabs the whole area should be paved in order to support the floor. A slab in each corner is not adequate.

Whatever base you use it is imperative that it is firm, flat and level otherwise your building will not fit together properly and will not last as long.

If you need to check the length, direction or quantity of bearers you need, exact floor measurements or further advice of please do not hesitate to contact us during office hours.

Suitable Bases

Not Suitable

Paving Slabs


Bearers/Sleepers On




Loose Bricks


Any uneven surface










To build a concrete base you will need the following:

  • Building Sand

  • Cement

  • Hardcore

  • Timber (for shuttering)

  • Timber (for a tamp)

  • Screws or nails

  • Tape Measure

  • Sweeping Brush

Once you've picked your location, measure out an area that is 5cm larger than your building on all sides. Remove any vegetation from this area and dig down 6 inches (or less if you want the base to be raised above ground level).

Timber frame (shuttering)

For the concrete to take the shape of your base you'll need to measure and cut a timber framework to line the edges, ensure that this is sitting perfectly flat on the ground, and flatten out the entire surface using a spade and rake. Next put down a 3 inch layer of hardcore and cover generously with sand.

For the concrete you can either mix 1 part cement to 5 parts ballast, or use a pre made dry concrete mix.

  • Slowly add water to the mixture, ensuring that it does not become too sloppy.

  • Spread the concrete evenly into the framework, filling to slightly above the timber.

  • Use another long piece of timber to level off the cement, rest the wood against the framework and move across it in a slow sawing motion to level out all of the concrete.

  • If wet weather is likely cover the base with plastic or tarpaulin for 24 hours.

  • In particularly hot or dry conditions covering with damp sacks and topping up with water occasionally can prevent your base from cracking as it dries, also laying a plastic membrane first can assist in keeping a residue of moisture in the concrete, to aid not cracking.

Paving Slab Base

If you decide to build your shed base using paving slabs instead you’ll need:

  • Pegs and string

  • Flat Face Paving Slabs

  • Grit/ sharp sand

  • Standard cement

  • Rake

  • Tape measure

  • Spade

  • Rubber mallet

  • Sweeping brush

Choose your location carefully and measure out the area for your base as outlined above in the concrete base guide, measuring to the nearest complete slab. Dig down to the required depth, usually around 2.5cm, but will differ depending on the thickness of your paving slabs and whether you want a level or raised base.

Next combine one part cement with eight parts building sand to make a dry mixture. Spread this evenly across the base area, around 4cm deep, and level out with a rake. Working out from a corner lay each slab and tap into position using a rubber mallet, constantly checking the flatness with a spirit level and ensuring all slabs are in line with each other. Do one last check with a long straight edge, making any adjustments to ensure a perfectly level surface, and brush away any excess sand or cement.

Starting out with a solid, level base will make things much easier when it comes to building your shed, and will protect the building from damp or muddy conditions. Even for relatively simple projects like this it's vital that you choose the best selection of tools and materials. Our expert advice and comprehensive range of products will save time and ensure that your project runs smoothly.