Familiarity or Scrutiny? Specifying Roof Coatings

CPD learning outcomes

By the end of this article, readers should be able to:

• Explain why certain industrial roof coating systems persist in specifications even though they may not be relevant.
• Identify how “legacy specification” behaviour can unintentionally increase your professional risk.
• Recognise where historic assumptions about metal roof refurbishment may no longer align with current understanding.
• Describe the characteristics of a modern, defensible specification for industrial pitched roof coatings.
• Formulate reflective questions to test whether a proposed specification remains appropriate, proportionate, and defensible.

A familiar pattern in specification creation

Many industrial roof coating specifications originate from historical project templates, lightly edited NBS clauses, or manufacturer literature incorporated years earlier and never updated.

Once embedded into a specification template, these references tend to persist because of inertia, fear of change or maybe even a management decision that hasn’t been challenged in years.

You’ll often hear “we always specify this manufacturer, because it’s already in the template.”

Surveyors are rarely given the time or commercial incentive to re-assess coating chemistry, failure modes, or certification scope unless a problem has occurred.

The result is not negligence, but inertia, which is a natural outcome of a profession that values consistency and risk control.

How legacy specifications are formed and why they persist

In practice, most industrial roof coating specifications are derived from:

• Historic project specifications reused as templates;
• NBS clauses that have been lightly edited over time; and
• Manufacturer system descriptions incorporated years earlier and never revised.

Once a system has been specified, delivered, and not obviously failed, it becomes part of the “safe vocabulary” of specification writing.

Although understandable, this approach ignores defect-led decision-making.

Why familiarity can feel safer than reassessment

From a professional indemnity perspective, specifying a system that has been used “many times before” can feel defensible because it is known, recognisable, and unlikely to be challenged during procurement.

However, this sense of safety is often retrospective rather than technical. The more robust question is whether the system still reflects:

• Current understanding of metal roof failure mechanisms;
• Modern coating chemistry and compatibility considerations;
• updated fire & building control requirements;
• Today’s expectations around durability, inspection, and maintenance planning; and
• The certification scope and limitations relevant to the proposed use.

When a specification is challenged because of premature failure, tenant dispute or end-of-life issues it is typically the rationale for the choice, rather than the familiarity of the name, that is tested.

Where historic assumptions can fall short

Assumption 1: Lap sealing is always beneficial

It was long assumed that sealing the joints between overlapping roof sheets at the mid-lap areas would universally improve roof performance. In practice, indiscriminate lap sealing can trap moisture, mask underside corrosion, and complicate future inspection and maintenance.
Where lap sealing is specified, the purpose, detailing, and potential consequences should be explicit.

Assumption 2: Cut-edge corrosion is secondary

Cut edges were often treated as a secondary issue within broader coating work. However, cut-edge corrosion is frequently
the first and most critical failure point on profiled steel roofs. A specification that does not address cut edges
explicitly may fail to align with observed roof pathology.

Assumption 3: All “silicone-type” systems behave the same

Polymer technologies vary materially in adhesion behaviour, repairability, self-bonding between coats, and sensitivity to moisture during application.

Treating different chemistries as being interchangeable oversimplifies a technically nuanced area.

A defensible specification reflects the known limitations and suitability of the proposed coating chemistry.

The professional risk of unexamined legacy systems

The risk is not that a legacy system is inherently “wrong”.

The risk lies in specifying without current justification, for example;

• Relies on outdated assumptions,
• Does not provide an appropriate response to the primary defect mechanisms present,
• Lacks certification scope aligned to the proposed application,
• Introduces avoidable maintenance or inspection constraints, or
• Creates future compatibility issues for repairs or extensions,

then the specification may become difficult to defend, even if it has historically been common practice, particularly in dilapidations and pre-letting contexts where proportionate, evidence-led recommendations are expected.

What a modern, defensible roof coating specification looks like

A contemporary specification for industrial pitched roofs should be defect-led, evidence-based, and proportionate.

Common features include:

1) Defect-first thinking

The specification should respond directly to observed defects, particularly at cut edges and other known failure points, rather than applying a generic system specification by default.

2) Appropriate use of standalone treatments

Where cut-edge corrosion is the primary defect, targeted treatment of the defect is probably more appropriate than blanket measures that introduce new risks (including moisture trapping and hidden corrosion) and increased costs.

3) Clear understanding of coating chemistry

The behaviour, limitations, compatibility, and practical repairability of the proposed polymer technology should be understood and documented.

4) Certification scope aligned to the application

Third-party certification should align with the proposed use case and substrate conditions, not simply the product family.

Where certification is relied upon, its scope and limitations should be checked and reflected in the specification.

In other words, read any supporting certification.

Professional specifiers need to understand for example, the exact scope of a BBA certificate and whether it is appropriate for the intended use.

5) Consideration of future maintenance

A defensible specification anticipates future inspection, repair, and intervention, including how later works will be achieved without compromising performance or compatibility.

The question worth asking

If this specification were reviewed or challenged in five or ten years’ time, would the technical rationale still stand up?

This question is often a more reliable test than “what has always been specified?”, because it focuses attention on evidence, proportionality, and professional defensibility.

Conclusion

Industrial roof coating specifications do not remain unchanged because the industry is static.

They remain unchanged because professional systems reward familiarity and discourage reassessment unless failure occurs.

As understanding of metal roof pathology improves and as coating technologies evolve, there is increasing value in revisiting long-standing assumptions.

This is not about novelty. It is about ensuring that specifications remain appropriate, proportionate,
and professionally defensible in today’s context.

Reflective questions (CPD)

Use the questions below to test and record your own decision-making process when preparing or reviewing an industrial roof coating specification:

1. Defect alignment: What is the primary defect mechanism observed (e.g., cut-edge corrosion, coating breakdown, fastener deterioration, lap-related leakage), and how explicitly does the specification respond to it?
2. Assumption check: Which elements of the proposed approach rely on historic assumptions (for example, lap sealing) and what evidence supports their use in this specific scenario?
3. Chemistry and compatibility: What coating is proposed, and what are the known limitations regarding moisture conditions, inter-coat adhesion, repairability or compatibility with existing treatments?
4. Certification scope: What third-party certification is being relied upon, and does the scope match the substrate, detailing, and intended performance requirements of this project? Have you examined the certification?
5. Future maintenance: How will the roof be inspected, repaired, and maintained after the works, and does the specification enable future interventions without disproportionate risk?
6. Professional defensibility: If this specification were challenged in five or ten years’ time, what would your technical rationale be, in one paragraph?

CPD note

This article forms part of Liquasil’s CPD programme for building surveyors and construction professionals, focusing on evidence-led roof refurbishment and defect-driven specification.

For CPD session availability and related technical guidance, please visit the Liquasil CPD page.