Do Bunded Oil Tanks Need a Base? UK Regulations, Requirements & Best Practice
When installing a bunded oil tank, one of the most common — and important — questions homeowners ask is: does a bunded oil tank need a base?
The short answer is yes. A solid, level base is a legal and practical requirement in the UK and plays a vital role in safety, compliance, and the long-term performance of your oil storage system.
In this guide, we explain why a bunded oil tank needs a base, what UK regulations say, the best materials to use, and what can go wrong if this step is overlooked.
Why Does a Bunded Oil Tank Need a Base?
A bunded oil tank can weigh well over three tonnes when full, so the surface it sits on must be able to support that load safely and evenly.
Key reasons a base is essential include:
Weight Support
A full oil tank places significant pressure on the ground beneath it. Without a proper base, the tank can sink, crack, or become distorted over time.
Stability & Alignment
A level base prevents movement and tilting, which can stress joints, valves, and the tank structure itself.
Leak & Spill Prevention
An unstable tank is far more likely to develop leaks. A solid base helps protect your property, surrounding land, and water sources.
UK Regulations for Oil Tank Bases
UK regulations clearly state that oil tanks must be installed on a suitable, stable base. These requirements are set out by OFTEC and government environmental guidance.
According to OFTEC’s guidance on domestic liquid fuel storage up to 3,500 litres, oil tanks must be installed on a firm, level, and non-combustible foundation.
Government guidance also confirms that improper installation — including poor foundations — increases the risk of pollution incidents and enforcement action:
https://www.gov.uk/guidance/storing-oil-at-a-home-or-business
Key Base Requirements at a Glance
Must be level and stable
Must support the full weight of the tank when filled
Must be made from non-combustible materials
Must extend at least 300mm beyond the tank footprint on all sides
What Is the Best Base for a Bunded Oil Tank?
Concrete Base (Recommended)
Minimum thickness: 100mm
Reinforced where possible
Long-lasting and extremely stable
Paving Slabs
Must be laid on a fully compacted sub-base
Slabs should be evenly supported with no rocking
Joints should be tight and level
Gravel, soil, decking, or plastic bases are not compliant and should never be used.
How to Prepare the Ground for an Oil Tank Base
Proper preparation is just as important as the base itself:
Clear the area of vegetation, roots, and debris
Excavate and level the ground
Compact the sub-base to prevent settlement
Install the concrete or paving slabs on a firm foundation
Skipping these steps often leads to uneven settling — one of the most common causes of oil tank failure.
What Happens If You Don’t Use a Proper Base?
Failing to install a bunded oil tank on a compliant base can result in:
Tank distortion or cracking
Increased risk of oil leaks and spills
Environmental contamination and clean-up costs
Invalid insurance cover
Breach of UK environmental regulations
In serious cases, oil leaks can result in thousands of pounds in remediation costs and potential legal action.
Choosing the Right Oil Tank & Professional Support
If you’re installing or replacing a tank, choosing the right product and installer is essential. Professional suppliers ensure tanks meet current UK standards and advise on correct base preparation.
For oil tank installation support and heating services, you can explore OTP Energy’s full offering here:
https://otpenergy.co.uk/#services
You can also browse oil and heating-related products via OTP Energy’s shop:
https://otpenergy.co.uk/shop-2/
Final Thoughts: A Proper Base Is Not Optional
So, do bunded oil tanks need a base? Absolutely. A compliant base is essential for safety, legality, and longevity. It protects your tank, your property, and the environment — while helping you avoid costly repairs and regulatory issues.
If you’re planning a new installation or replacing an existing tank, make sure the base is treated as a non-negotiable part of the process.
For compliant oil tank solutions and expert advice, OTP Energy is here to help you get it right first time.
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