How to Lay a Concrete Shed Base (UK Guide) | Pound House LTD

If you’re planning to install a garden shed, workshop, or outdoor storage building, getting the base right is one of the most important parts of the entire project.

A solid concrete shed base provides the strength, stability, and long-term durability your shed needs. Without a properly laid foundation, sheds can become uneven, suffer from water damage, or even shift over time.

At Pound House Ready Mix Concrete, we regularly supply concrete for domestic projects across Kent, and shed bases are one of the most common applications. The good news is that with proper planning, laying a concrete shed base can be a straightforward job.

This guide covers everything you need to know.

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Why Choose a Concrete Shed Base?

Concrete remains one of the most reliable options for shed foundations in the UK due to its:

• Long lifespan
• Excellent load-bearing strength
• Resistance to rot and moisture
• Low maintenance
• Suitability for heavy sheds, workshops, or garden offices

Compared to timber or paving slabs, a concrete base generally offers better long-term performance.

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What Size Should a Shed Base Be?

Your concrete base should usually be slightly larger than the shed itself.

General rule:

• Add approximately 100mm (4 inches) extra on each side

This helps improve stability and prevents water sitting directly against the shed walls.

For example:

8ft x 6ft Shed:

Recommended base size:
8ft 8in x 6ft 8in

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Tools and Materials You’ll Need

Materials:

• Ready mix concrete
• Hardcore or MOT Type 1 sub-base
• Timber for formwork
• Damp proof membrane (optional)
• Steel mesh reinforcement (for heavier structures)

Tools:

• Shovel
• Spirit level
• Wheelbarrow
• Tape measure
• Wooden float
• Tamper or compactor

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Step-by-Step: How to Lay a Concrete Shed Base

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Step 1: Mark Out the Area

Measure and mark the area carefully using string lines and stakes.

Make sure:

• The area is square
• Dimensions are accurate
• Ground is level

Taking time here avoids problems later.

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Step 2: Excavate the Ground

Remove grass, topsoil, and loose material.

Recommended depth:

• Around 100–150mm for most domestic shed bases

This depth allows space for:

• Sub-base
• Concrete slab

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Step 3: Add and Compact the Sub-Base

Lay a sub-base of hardcore or MOT Type 1.

Typical thickness:

• 50–75mm

Compact it thoroughly to create a stable foundation.

A strong sub-base is essential for preventing movement or cracking.

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Step 4: Build the Formwork

Use timber boards to create a frame around the perimeter.

Ensure:

• Boards are level
• Corners are secure
• Dimensions match your shed base plan

This formwork shapes the concrete as it cures.

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Step 5: Pour the Concrete

Pour your ready mix concrete evenly into the frame.

Recommended concrete thickness:

• 75–100mm for standard sheds
• Thicker for heavier buildings

Spread and level the concrete using a straight edge.

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Step 6: Level and Finish

Use:

• Screed board
• Float

to smooth the surface and remove imperfections.

Check levels carefully throughout.

A flat, level finish is essential for proper shed installation.

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Step 7: Allow the Concrete to Cure

Concrete needs time to gain strength.

Typical timeline:

• Light foot traffic: 24–48 hours
• Shed installation: 7 days minimum
• Full cure: 28 days

Protect the slab during curing, especially in hot or wet weather.

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Common Mistakes to Avoid

Some of the most common shed base issues include:

• Poor ground preparation
• Insufficient sub-base
• Incorrect slab thickness
• Uneven formwork
• Rushing curing time

Taking shortcuts at the base stage often leads to expensive issues later.

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Should You Use Ready Mix Concrete?

For most shed base projects, ready mix concrete is often the easiest and most reliable option.

Benefits:

• Consistent strength
• Saves time
• Reduces mixing errors
• Better for larger bases
• Professional finish

At Pound House Ready Mix Concrete, we supply high-quality concrete suitable for shed bases, patios, driveways, and more.

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Final Thoughts

Laying a concrete shed base properly is one of the best investments you can make for your outdoor structure.

With correct preparation, quality materials, and proper curing, your concrete base can last for decades while providing reliable support for your shed.

For homeowners and builders across Kent, choosing the right concrete supplier can make the process faster, easier, and far more dependable.

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FAQs – Concrete Shed Bases

How thick should a concrete shed base be?

Typically 75–100mm for standard garden sheds.

How long before I can put a shed on concrete?

Usually after at least 7 days, although full curing takes 28 days.

Do I need reinforcement for a shed base?

For heavier sheds or workshops, steel mesh reinforcement can improve durability.

Can I lay a shed base myself?

Yes, many domestic shed bases can be completed as DIY projects with proper preparation.

Is concrete better than slabs for a shed base?

In most cases, concrete provides greater strength, durability, and longevity.