Shed Bases

More sheds get ruined by what is underneath them than by anything that happens above. A shed on uneven ground racks, and then the door stops shutting, the roof opens up at the ridge and water gets in. Here is what we tell people before they order.

The rule

Flat, firm, and the same size as the shed or a touch smaller, never bigger. A base that sticks out past the walls collects rain against the bottom boards, and that is how floors rot from underneath. Level matters more than what it is made of. About 10mm of fall across an 8×6 is enough to stop a door latching.

Your four options

Existing concrete or slabs

If it is flat and sound, use it. Check with a long spirit level across both diagonals, not just one edge. Slabs that have sunk at a corner can usually be lifted and rebedded on the day.

Timber bearers

Pressure treated bearers on a compacted bed, lifting the floor clear so air moves under it. Cheapest honest base there is, and the right answer on ground that already drains.

Plastic grid or combi base

Interlocking grids filled with gravel. Water goes through instead of pooling, and it is a lot quicker and cleaner than mixing concrete. This is what we fit most, and it suits the clay round here where a solid slab can trap water at the edges.

Poured concrete

Over the top for a 6×4 and exactly right for a 12×8 workshop with machinery in it. Wants a damp proof membrane underneath and a week to cure before anything goes on top.

What it costs

Bearers start around £50 and a combi base is priced on the footprint of the building. Both get added at checkout and laid by our fitters before the shed goes up, so there is no second visit and no hanging about waiting for concrete to go off.

Not sure what you have got?

Send us a photo of the spot with a tape measure in it and we will tell you straight whether your base will do. Costs us nothing to say yes.