Shed Bases and Concrete Bases in Southampton

Sizing a shed base properly

The base should be slightly larger than the footprint of the building so rainwater drips off the roof on to the concrete rather than soaking the bottom of the walls. Check the manufacturer's base size for your shed or summerhouse before we mark out, because some kits measure from the roof overhang and others from the floor frame. Leave space around the sides to reach the walls for treatment and maintenance.

Think about the door too. A small apron of concrete or slabs in front of the door stops a muddy patch forming where you step in and out.

What goes under a concrete pad

Concrete laid straight on to topsoil cracks and tilts as the soil moves. We strip the topsoil and dig down to firm ground, then lay and compact a hardcore sub-base in layers. On clay, which is common across Southampton and the surrounding towns, that firm layer stops seasonal shrinking and swelling showing through as cracks.

Larger pads and anything carrying a heavy load, such as a filled hot tub or a workshop with machinery, may need reinforcement mesh and a thicker slab. We work that out from the load rather than using one thickness for every job.

Concrete or slabs for a shed base?

Both work when the ground underneath is right. A concrete pad suits larger buildings, heavy loads and bases that need to be one solid piece. A slabbed base is quicker to lay, easier to lift later and can look neater if it is visible around the building. Our guide to slabbing for sheds and bases covers the slab option in detail.

• Concrete: one solid slab, best for heavier buildings and hot tubs
• Slabs: quicker, can be relaid later, tidy where the edges show
• Either: needs a dug and compacted sub-base to stay level

Curing and when you can build on it

Fresh concrete needs time to gain strength before it carries a building. We protect it from heavy rain and frost while it cures and give you a clear date for putting the shed or summerhouse on. Bases are a good job for autumn and winter as long as hard frost is avoided, so the building is ready to go up in spring.

A shed base that keeps the building level

A shed is only as good as what it stands on. A base that is out of level twists the frame, so doors stick and panels gap, and a base that sits in damp ground rots the floor from below. A concrete base for a shed is dug out, built on compacted stone, shuttered to size and poured level, so the building sits square and dry for its whole life.

Size matters here. The base is cast slightly larger than the shed so rain drips clear of the walls, and the finished height is set so the floor stays above the surrounding ground. These are small decisions on the day that decide whether the shed lasts.

Concrete base or wooden shed base?

A wooden or plastic grid base is lighter and quicker, and for a small, light shed on firm, level ground it can be enough. Concrete suits heavier buildings, summerhouses, workshops and hot tubs, anywhere the weight is high or the ground is soft, and anywhere you do not want to think about the base again. Slab bases sit between the two: quicker than concrete, firmer than timber, and easier to lift years later.

Ashley will tell you which your building needs on the visit. Where the ground is soft or sloping, the answer is almost always concrete, because everything else follows the ground down.

Bases for more than sheds

The same build carries summerhouses, garden offices, log stores, bin and bike stores and hot tubs. Hot tubs in particular need a base designed for the filled weight, which is far heavier than any shed. If the base is part of a wider project, the hard landscaping page explains how it fits with the paving and paths around it.