Shed base installation

A shed base does a simple job that is easy to underestimate: it keeps the building level, square and clear of standing water for as long as the shed lasts. When a door starts to stick, the floor feels springy or the corners lift, the cause is usually the ground underneath rather than the shed itself. A properly built base removes that problem before it starts.

Gardenscape has provided hard and soft landscaping since 2007, and a shed base is often a small but important part of a wider garden project. Tell us the size of the building, where it will sit and what it will store, and we can talk through the most suitable type of base for your garden.

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Concrete base or paving slabs

The two most common options are a poured concrete base and a base laid in paving slabs. A concrete base is cast as one solid pad on a compacted sub-base, which suits heavier buildings, workshops and garden rooms, or sheds that will hold mowers, tools and bikes. Slabs laid on a compacted bed can work well for lighter sheds and are easier to lift and reuse if the garden changes later.

Whichever is chosen, the base should be slightly larger than the shed footprint or sized to the manufacturer's guidance, so the walls sit fully on the solid surface and rain runs away from the timber. A base that is too small lets water drip onto the edge and soak back under the floor.

What is involved

The work starts with marking out and removing turf and topsoil until firm ground is reached. A layer of hardcore is then compacted in stages to form the sub-base. For a concrete base, timber formwork is set to level and the concrete is poured, tamped and finished. For a slab base, a bed is laid and each slab is set level and checked against its neighbours.

Levels matter more than people expect. A shed base should be flat so the building stays square, while the surrounding ground should fall away so water does not collect against it. On a sloping garden, one side may need building up or the ground cut back, and that part of the job takes more time than the base itself.

Access, position and the ground beneath

Think about where the door will open, how you will reach the shed in wet weather and whether a path is needed from the house. Leaving a gap between the shed and fences or hedges makes it possible to treat timber and clear leaves. Bases built hard against a boundary often trap damp.

Soft ground, old tree roots, made-up soil and poor drainage all affect how deep the excavation needs to go. If a previous base has sunk or cracked, it is worth finding out why before building a new one in the same place. Our guide to a sinking shed base explains the usual causes.

What affects the cost

The size of the base, the type chosen, how much digging and waste removal is needed, the slope of the ground and how easy it is to bring materials through to the back of the garden all shape the price. Narrow side access or a long carry from the road adds labour. We look at all of this on a free site visit and then give one fixed written quote.

Your questions answered

Is a concrete or slab shed base better?

Concrete suits heavier buildings, workshops and garden rooms, while paving slabs on a compacted bed can suit lighter sheds and are easier to lift later. The right choice depends on the building, its contents and the ground.

How big should a shed base be?

It should match the shed footprint or the manufacturer's guidance, so the walls sit fully on the base and rainwater runs away from the timber rather than dripping onto the edge.

How long does it take to build a shed base?

Most of the time goes into digging out, compacting the sub-base and setting levels. A concrete base also needs time to cure before the shed goes on, so the overall timescale depends on size, ground and weather.

What affects the cost of a shed base?

Size, the type of base, how much excavation and waste removal is needed, the slope of the garden and access for materials. We price it after a free site visit with one fixed written quote.