Shed bases and installation: getting the foundation right

Why the base matters

If a shed sits directly on soil or grass, its floor stays damp and rots. If the base is not level, the frame twists, which is why doors stop latching and windows crack. Water also needs to run off the base rather than collecting beneath the floor.

Shed base options compared

Each has a place depending on the shed and the site.

• Concrete slab: solid and permanent, best for large or heavy buildings and workshops.
• Paving slabs: firm and level if laid on a compacted sub-base, suits most garden sheds.
• Timber frame base: treated bearers on supports, useful on sloping ground or where digging is difficult.
• Plastic grid: quick to lay on a prepared surface, filled with gravel for drainage.

Positioning the shed

Leave a gap around the shed so you can reach every side for treatment and repairs, and so air can circulate. Keep it clear of overhanging trees that drop leaves into gutters, and think about the route to it in winter. If you want power, plan the cable route before the base is laid.

What installation involves

Once the base is ready, the floor goes down, walls are fixed together, the roof is fitted and covered with felt or another covering, then doors, windows and trims. Fixings, sealing the roof edges and treating any cut timber make a real difference to how long the shed lasts. Most sheds are typically assembled in a day, larger ones longer.

Planning and permitted development

Many garden sheds are typically built without planning permission under permitted development, but height limits apply, especially near boundaries, and different rules apply to listed buildings and conservation areas. Check with your council if the shed is large or close to a boundary.

Making a shed last

Treat the shed as soon as it is built if it arrived untreated, and again every few years. Pay attention to the bottom edges of the cladding, the door and the roof overhangs, which take the most weather. Check the roof covering each autumn and replace damaged felt before water reaches the boards.

Ventilation matters more than most people think. A shed sealed up tight with tools, bikes and garden furniture can become damp inside, which rusts metal and marks wood. A small vent high on each gable end lets moist air out. If the shed will be used as a workshop, think about security at the same time: solid hinges, a proper lock and screws that cannot be undone from outside.

If the shed will hold heavy items such as a workbench, a ride on mower or stacked logs, mention it at the planning stage so the floor and base can be specified for the load.

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