Bund Lining Guide: Regulations, Materials and Repair
Bund lining is the application of a chemically resistant, liquid-tight coating to the walls and base of a bund – the containment structure built around tanks storing oil, chemicals or other hazardous liquids. Its job is to make the bund genuinely impermeable, because bare concrete is not. This guide covers the regulations, the materials and how failed bunds are repaired.
Key takeaways
- Bare concrete bunds leak. Concrete is porous, cracks over time and is attacked by many stored chemicals, so an unlined bund often fails the basic requirement of containing a spill until it can be recovered.
- UK oil storage regulations require secondary containment of at least 110 percent of the largest tank and the Environment Agency expects bunds to be impermeable to the stored liquid.
- CIRIA C736 is the recognised design and assessment guidance for containment systems. Insurers and the EA both lean on it, so lining specifications are usually written to it.
- The lining must be matched to the stored chemical. Epoxy handles oils and many aqueous chemicals, vinyl ester handles acids and solvents and polyurea suits large or complex bunds needing fast-cure elastomeric coverage.
- Most bund failures start as hairline cracks, blowholes or joint movement. Lining works are as much concrete repair as coating, so condition survey and substrate preparation decide the outcome.
What is bund lining?
Bund lining is a seamless protective coating applied to the internal surfaces of a bund to make it liquid-tight and resistant to the substance it may one day have to contain. A lined bund holds a spill without leaking into the ground or attacking the concrete, buying time for the spill to be pumped out and dealt with safely. It is one of several ways to achieve compliant containment – integral waterproof concrete, sheet membranes and steel bunds all exist – but for the ageing concrete and masonry bunds found on most UK sites, a resin lining is the usual remedial route and it is what this guide covers.
Bunds sit around fuel tanks, chemical storage, transformer compounds, process vessels and tank farms. Most are concrete or masonry and both materials are porous. Without a lining, a spill of oil or aggressive chemical can migrate through the structure and into soil or groundwater within hours – which in regulatory terms is a pollution event even if the bund walls held.
What are the UK regulations for bunds?
The core requirement comes from the Control of Pollution (Oil Storage) (England) Regulations 2001 with parallel but not identical regimes in Scotland, Wales and Northern Ireland: secondary containment must hold at least 110 percent of the largest tank’s capacity, or 25 percent of total capacity for multiple tanks if that is greater – and the bund must be impermeable to oil and water. For chemicals, containment duties arise through environmental permit conditions and, on sites storing dangerous substances above qualifying thresholds, the COMAH regulations – COMAH is not a general bund rule and most smaller chemical stores fall outside it.
The word doing the work is impermeable. A structurally sound bund that seeps is non-compliant and the Environment Agency’s guidance makes the operator responsible for maintaining containment integrity, not just building it. Penalties scale with harm – pollution of a watercourse from a failed bund is prosecuted under the Environmental Permitting Regulations – and insurers increasingly ask for evidence of containment condition at renewal. Lining is how an ageing but sound bund is brought back to demonstrable impermeability.
What is CIRIA C736?
CIRIA C736, Containment systems for the prevention of pollution, is the UK’s recognised technical guidance for the design, assessment and maintenance of secondary and tertiary containment. It replaced the earlier C535 and it is the document the Environment Agency, designers and insurers all reference when judging whether a containment system is fit for purpose.
For lining work its relevance is practical. C736 sets out containment classifications based on risk, expectations for joint sealing and crack treatment and the principle that a containment system should be assessed as a whole – walls, base, joints, penetrations and surface protection together. A lining specification written to C736 therefore starts with a condition assessment of the structure rather than jumping straight to a coating product, which is exactly the right order of operations.
Why do concrete bunds fail?
Concrete bunds fail through cracking, joint movement, surface porosity and chemical attack – usually in combination. Shrinkage and thermal movement open hairline cracks, day joints and movement joints lose their sealant, blowholes and honeycombing leave permeable paths and stored chemicals attack the cement matrix itself.
Aggressive acids attack cementitious material – how fast depends on the chemical, its concentration and temperature. Oils penetrate and weaken the surface over years. Even rainwater standing in an outdoor bund freezes, thaws and gradually opens the structure. Moisture in the slab matters too: resin applied over a damp substrate can blister osmotically or fail to bond, which is why moisture testing is part of any competent survey. The failure mode that matters is rarely collapse – it is the slow loss of impermeability that nobody notices until a spill or an inspection. This is why concrete repair and crack treatment are integral to bund lining rather than a separate trade.
Which lining material is right for which chemical?
The lining must resist the stored substance at the concentration and temperature it could realistically be spilled at. The table below shows typical duties only – actual compatibility varies by product formulation, so every specification is verified against the manufacturer’s chemical resistance data for the exact substance stored, never against a generic table:
| Lining system | Typical duty | Strengths | Limitations |
|---|---|---|---|
| Epoxy coatings | Fuel oils, diesel, lubricants, many aqueous chemicals | Excellent adhesion, hard wearing, economical | Limited against strong acids and some solvents; rigid, so cracks if the substrate moves |
| Vinyl ester and novolac epoxy | Acids, alkalis, aggressive solvents | Outstanding chemical resistance including concentrated acids | Higher cost; application is specialist and condition-sensitive |
| Polyurethane coatings | General chemical duty with some flexibility | Tolerates minor movement, good abrasion resistance | Chemical range narrower than vinyl ester |
| Polyurea (spray applied) | Large bunds, complex shapes, fast turnaround | Elastomeric so bridges cracks, cures in seconds, seamless over detail | Needs specialist spray plant; chemical resistance grade must be checked per product |
Glass fibre reinforcement can be laminated into epoxy and vinyl ester systems where the structure needs extra tensile strength across static cracks. Genuinely live cracks and movement joints are a different problem – they need engineered joint details that accommodate the movement, not a coating bridged over them. The specification order is structure first, chemical second, movement third, budget last – a cheap lining that the stored acid dissolves is not containment, it is decoration.
How is a bund lined or repaired?
Bund lining follows a fixed sequence: condition survey, cleaning and preparation, concrete repair, joint treatment, lining application and integrity testing. The survey establishes what the structure needs and confirms the stored chemical, because the coating choice hangs on it.
Preparation means removing contamination and laitance, usually by abrasive blasting or grinding, so the lining bonds to sound concrete – the same discipline as any floor preparation work. Defective concrete is cut out and reinstated with repair mortars, cracks are routed and filled and joints are sealed with chemically resistant sealants or bandaged with reinforcement. The lining then goes on in multiple coats to the specified thickness, paying particular attention at wall-to-base junctions, pipe penetrations, plinths and sumps, which is where most leaks start. On completion the works are verified to suit the project – spark testing finds pinholes on suitable coating systems and hydrostatic testing, where specified, proves the bund holds liquid. A completion pack recording coating thickness, test results and materials used is worth asking for, because insurers and regulators increasingly want documented evidence of containment condition. Lining work is normally carried out with tanks in place, isolated and with the bund taken out of service for the preparation, application and cure period – downtime is one of the practical questions the survey answers.
How often should a bund be inspected?
Visual checks should be routine – monthly is a common regime – with a formal condition inspection at least annually and after any spill. CIRIA C736 recommends periodic systematic assessment of containment systems and insurers and EA permit conditions often set their own intervals.
The things to look for are contaminated or unexplained standing liquid, blocked drainage, cracking, sealant loss at joints, coating blisters or delamination and staining on the external face that suggests seepage. Rainwater in an open outdoor bund is expected – the concern is liquid that should not be there or water that cannot be drained to allow inspection. A lined bund in good condition needs little more than cleaning; catching a failed joint early is a small repair, while a season of unnoticed seepage can mean contaminated ground and a rebuilt bund.
Frequently asked questions
Does a concrete bund need to be lined?
If the existing structure can demonstrably contain the stored substance without seepage, no – the legal test is impermeability, not the presence of a lining. In practice most ageing concrete bunds cannot demonstrate that, because concrete is porous, cracks over time and is attacked by many stored substances, so lining is the usual route back to compliance.
What is the 110 percent rule for bunds?
UK oil storage regulations require secondary containment to hold at least 110 percent of the capacity of the largest tank within it. For multiple tanks the requirement is 110 percent of the largest tank or 25 percent of total capacity, whichever is greater.
What is the best coating for a fuel oil bund?
A multi-coat epoxy system is the standard choice for diesel, heating oil and lubricant bunds in typical conditions. It resists hydrocarbons well, bonds strongly to prepared concrete and is economical over large areas. The survey confirms it suits the specific bund – and acid or solvent storage needs vinyl ester or novolac epoxy systems instead.
Can a leaking bund be repaired without rebuilding it?
Usually yes, if the structure is sound. Cracks are routed and filled, defective concrete is reinstated, joints are resealed and a new lining is applied over the repaired substrate. Rebuilding is only needed where the structure itself has failed or the bund is undersized for the tanks.
How long does a bund lining last?
A correctly specified and applied lining typically lasts 10 to 20 years depending on chemical exposure, weathering and mechanical damage. Longevity depends more on surface preparation and matching the coating to the stored chemical than on the product brand.
What is spark testing on a bund lining?
Spark testing (holiday testing) passes a high-voltage probe over the cured lining. Any pinhole or thin spot lets the current arc to the conductive concrete beneath, pinpointing defects invisible to the eye so they can be repaired before the bund goes back into service.
Who is responsible for bund maintenance?
The site operator. UK regulations and permit conditions place the duty to maintain effective containment on whoever stores the substance and that duty continues for the life of the installation – which is why periodic inspection and timely relining matter.
Who carries out bund lining work?
Specialist coating contractors experienced in containment, concrete repair and chemically resistant systems. Surface Specialists is a network of vetted specialist contractors – tell us what the bund stores, at what concentration and roughly what size the structure is and we match your project to a contractor with the right containment experience, who surveys the structure and provides a written quotation.
Need a bund brought back to compliance? See our bund lining service, our concrete repairs service or the rest of our resin flooring systems. Companion guides: anti-static flooring explained and anti-slip R ratings.