How Thick Should a Concrete Shed Base Be?
The correct concrete thickness is essential for keeping your shed stable, level, and protected from long-term movement. This guide explains exact slab depths, reinforcement advice, and UK best practice for building a concrete shed base.
Recommended Concrete Thickness for Shed Bases
| Shed Size / Use | Concrete Thickness |
|---|---|
| Small sheds (6x4, 7x5) | 100mm (4") |
| Medium sheds (8x6, 10x8) | 100–125mm |
| Large or heavy-duty sheds | 125–150mm + reinforcement |
| Workshops / motorcycle sheds | 150mm reinforced concrete |
Tip: For sheds storing machinery or motorbikes, reinforcing mesh (A142) dramatically improves strength and longevity.
How to Build a Concrete Shed Base (Step-by-Step)
- Mark out the shed footprint, allowing 50–75mm extra on each side.
- Excavate to around 150–200mm depth.
- Lay and compact a MOT Type 1 sub-base.
- Install timber shuttering to form the slab edge.
- Add a damp-proof membrane (DPM).
- Pour concrete and level with a straightedge.
- Allow 7–28 days curing before installing your shed.
Official UK construction guidance: Designing Buildings – Concrete
Which Sheds Need a Concrete Base?
Concrete Base Cost in the UK
| Item | Typical Cost |
|---|---|
| Concrete (per m²) | £60 – £90 |
| Ground preparation | £20 – £40 per m² |
| Professional installation | £150 – £250 per day |
Frequently Asked Questions
Can I pour concrete directly onto soil?
No — always use a compacted sub-base and membrane to prevent cracking and movement.
How long should concrete cure before installing a shed?
Minimum 7 days, ideally 28 days for full strength.
Do I need planning permission?
Usually not, but always check:
Planning Portal guidance.
Next Steps
Once your base is complete, choose the right shed for your garden:
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