Garden Projects · 9 min read · Intermediate

How to Build a Shed Base: Concrete, Paving or Timber Options

Choose and prepare a firm, level shed base so the building remains square, supported and separated from persistent ground moisture.

Key points & steps

Check the shed manufacturer’s required base dimensions and support arrangement before preparing the site. Some floors need continuous support while others use bearers or a proprietary grid.
Choose a site with practical access and drainage, allowing for roof overhang, door swing, maintenance access and nearby roots or vegetation.
Mark the footprint and check it is square by measuring diagonals. A base that starts out of square can make shed panels, doors and roof sections difficult to assemble.
For a concrete or paving base, remove soft topsoil and prepare a compacted sub-base appropriate to the ground and building size before the finished base layer is installed.
For a timber or plastic-grid base, follow the manufacturer’s support and gravel preparation requirements and ensure all load points are properly supported.
Make the finished base level across both directions. A twisted or sloping base can distort the shed over time and cause doors/windows to bind.
Avoid creating a base much larger than necessary if it leaves a flat ledge that directs rainwater back under timber wall panels.
Allow concrete/mortar to cure adequately before assembling the shed and check final dimensions once more before delivery or construction.

A firm level base matters more than simply choosing concrete over timber or plastic.
Large garden buildings, workshops or very heavy loads may need a more substantial foundation than a basic lightweight shed.
Keep timber components separated from standing water and maintain airflow where the shed design requires it.