Foundation Base Guide

How to Build a Shed Base: A Complete Guide to the Best Garden Building Foundations

Before assembling your garden building, shed, log cabin, or summerhouse, it’s crucial to ensure it sits on a firm, level, and durable base. In this guide, we’ll walk you through 3 ways to build your foundation base, explain why it matters, and help you choose the best location for long-lasting results.


Why You Need a Solid Shed Base

A proper foundation base is essential for the structural integrity and longevity of your garden building. Installing your shed on a strong and level foundation ensures:

  • Easy, accurate assembly of your shed panels.
  • Prevention of common issues like misaligned doors, water ingress, and warping.
  • Longer lifespan for your garden building due to reduced moisture and structural stress.
  • Protection for your product warranty, as incorrect base installation can void guarantees.

Without the right base, your structure may become unstable, difficult to use, and more vulnerable to weather damage.


Foundation Base Options

There are a number of durable base solutions to suit different garden surfaces and budgets:

  1. Concrete Slab Base – Extremely durable and long-lasting, ideal for large or heavy garden buildings.
  2. Paving Slab Base – A flexible, cost-effective solution that’s easy to install.
  3. Timber Frame Base – Suitable for uneven ground and perfect for raised sheds or sloped gardens.
  4. Plastic Grid Base – A lightweight, eco-friendly option that provides excellent drainage and ease of installation.


Where to Position Your Garden Structure Base for Best Results

Location matters just as much as the material. Here’s what to keep in mind when choosing where to position your shed base building 

Avoid tight spaces near walls or fences to account for roof overhang and allow air circulation.

  • Trim nearby trees or bushes to prevent damage from overhanging branches.
  • Ensure easy access around the building for maintenance, such as applying wood treatments or repairs.
  • Think about natural light and views, especially if the building will be used as a summerhouse, garden office, or hobby room.
  • Plan ahead for utilities like electricity or water, positioning your shed closer to mains supply if needed.

Also, consider the path you’ll take to reach your shed—minimise the need to carry heavy items long distances by placing it in a convenient, accessible part of the garden.


How to Build a Shed Base

A solid, level shed base is essential for ensuring your garden building stands strong, stays dry, and lasts for years.

Without a proper foundation, you risk issues like door misalignment, water damage, and even structural instability—plus, assembling on an incorrect base may void your warranty.

Below, we cover 3 of the best shed base methods—each offering unique benefits depending on your garden type, budget, and installation needs.


Method 1: Concrete Shed Base – Maximum Strength and Durability

Ideal for: Heavy garden buildings, year-round use, permanent setups.

Why it works:
A concrete shed base provides the most durable, weather-resistant foundation. It ensures your garden shed stays stable, even in adverse weather, and offers long-term structural integrity.

How to build a concrete base:

  1. Mark out your area slightly larger than the shed size (add 30–40mm to each side).
  2. Excavate and lay 75mm of compacted hardcore or rubble as the base layer.
  3. Add a level layer of compacted sand, then build a formwork frame using timber or steel rails.
  4. Mix and pour concrete (1 part cement to 5 parts all-in ballast), ensuring a consistent, not overly wet mix.
  5. Pour and spread evenly, compact in layers, and smooth using a float.
  6. Cover with a protective sheet to cure naturally—spray water in hot weather to prevent rapid drying.

Benefits:

  • Supports heavy structures like workshops or log cabins
  • Creates a level, stable surface for easy shed assembly
  • Minimises moisture damage and increases lifespan


Method 2: Paving Slab Shed Base – Flexible and DIY-Friendly

Ideal for: Medium-sized sheds, budget-friendly builds, or temporary placements.

Why it works:
A paving slab shed base is a cost-effective alternative to concrete. It provides a firm, flat surface with built-in drainage, making it perfect for smaller sheds or moderate-use garden rooms.

How to build a slab base:

  1. Clear vegetation, then mark and square the area using pegs and string.
  2. Excavate to a depth of 63.5mm (~2.5").
  3. Fill with a dry sand and cement mix (1 part cement to 8 parts sand).
  4. Level the base and begin laying paving slabs, starting from a corner.
  5. Use a rubber mallet to tap slabs into place, ensuring they are slightly raised to promote drainage.
  6. Check alignment and level each slab for a flush finish.

Benefits:

  • Quick and cost-effective to install
  • Built-in rainwater drainage
  • Easy to remove or relocate if needed


Method 3: Timber Bearer Shed Base – Fast and Great for Uneven Ground

Ideal for: Uneven surfaces, quick installations, sheds with built-in floors.

Why it works:
A timber bearer shed base uses pressure-treated wood or concrete bearers to elevate your garden building—protecting it from ground moisture and enabling ventilation underneath.

How to build with bearers:

  1. Clear vegetation and mark out the shed base area.
  2. Excavate to 50mm depth and fill with gravel or soil for drainage.
  3. Lay floor bearers (timber or concrete) perpendicular to your shed’s joists.
  4. Space bearers 400–600mm apart, adjusting for shed size.
  5. Use a spirit level and mallet to ensure everything is even.

Examples of bearer requirements:

  • 6×4 shed – 4 bearers (1150mm)
  • 8×6 shed – 5 bearers (1750mm)
  • 10×8 shed – 6 bearers (2350–2950mm, depending on joist direction)

Benefits:

  • Ideal for sloped or uneven gardens
  • Elevates shed, improving airflow and reducing damp
  • Fast and simple to install, great for DIYers


Final Shed Base Tips

  • Don’t build too close to fences or walls—allow room for roof overhang and maintenance.
  • Avoid positioning near trees—trim branches to prevent future damage.
  • Consider access and utilities like electricity or water when choosing a location.
  • Think about natural light and visibility, especially for summerhouses or home offices.

A properly built shed base sets the stage for a safe, long-lasting garden building. Whether you’re creating a garden office, workshop, or leisure space, choosing the right foundation method is key to success.

By following these simple but important steps, you'll lay the foundation for a secure, weather-resistant, and long-lasting DIY garden building.

Please ensure your base is ready prior to installation of your shed/cabin as this is NOT part of the installation service.