The Hidden Hazard in PAS 9980: Why Limited Sampling Betrays Building Safety

PAS 9980's limited "strategic" sampling creates a nightmare scenario for external wall assessments: unknown hazards lurking unseen across the cladding scheme. How can any assessor opine confidently on every critical element—cavity barriers, firestops, intumescent seals—when only a fraction is exposed? One missed or defective firebreak turns "tolerable risk" into catastrophe, as it breaches the defense-in-depth layered protections essential to life safety.

Why One Firebreak Matters So Much

Firebreaks form the last line of defense in external walls, designed to compartmentalize fire spread. Missing or failing just one exposes the entire system.

• System Failure: In defense-in-depth, firebreaks create redundancy—no single point of failure. One gap lets fire bypass controls, spreading unchecked across floors or cavities, as seen in Grenfell's cavity barrier failures.

• Regulatory Non-Compliance: Codes like Reg 7(2) and the Fire Safety Order demand verified performance of all barriers. PAS 9980's sampling shortcuts risk non-compliance verdicts, fines, and remediation halts—shifting burden to leaseholders.

• Catastrophic Consequences: Flames, smoke, and toxins race unimpeded, endangering lives, collapsing structures, and erasing assets in minutes.

• Cascading Failures: Like IT firewalls or process plant isolators, one cladding firebreak lapse triggers total system compromise—data breaches in cyber terms, or mass evacuation failure here.

• "Just One" Mentality: Dismissing a single defect as negligible prioritises cost over verification, echoing pre-Grenfell complacency.

From Paper to Peril: The PAS 9980 Trap

PAS 9980 extrapolates from minimal openings to rate whole walls "low/medium," codifying uncertainty as "tolerable." But fire safety isn't probabilistic gambling—it's ALARP: as low as reasonably practicable. Post-Grenfell science demands full exposure where doubt persists, not statistical comfort for dutyholders.

Access the full ICM paper critiquing this structural flaw from the Link below: It lays bare how sampling undermines Reg 7(2) intent, trapping residents in hazardous homes.

What Actually IS Tolerable? 

There is, at present, no meaningful control over who can be engaged to carry out a PAS 9980 assessment, nor over their real‑world competence, ethics, or commercial independence. In practice, the threshold of what is deemed “tolerable” often reflects the personal opinion of the assessor and the commercial agenda of those instructing them, not an objective, science‑backed standard.

Worse, that opinion is frequently formed from limited sampling without full exposure of all critical elements and often without robust testing evidence or fire science underpinning the conclusions. The result is that Class E, D and C materials—plainly combustible and far removed from true non‑combustibility—can be described as “tolerable” in the external wall, provided the narrative and scoring framework are made to fit.

There is nothing in the PAS that prevents its use to undermine the intent of Regulation 7(2), which requires materials of Class A2‑s1,d0 or better, and was clearly conceived as a move away from combustible façades in higher‑risk buildings. The old “limited combustibility” definition for A2‑s3,d2, with a gross calorific value up to 3 MJ/kg, sits in the same calorific band that Regulation 7(2) mandates for A2‑s1,d0; the difference is meant to be in smoke and droplet performance, yet this nuance is routinely lost when “tolerable” is used to justify retaining combustible build‑ups.

Leaseholders have come to understand this as gaming the system: using a compliant‑looking PAS 9980 report and an EWS1 form to normalise ongoing combustibility while shifting the practical consequences onto residents. Once lenders and insurers see a certificate that acknowledges combustible materials but still labels the situation “tolerable”, premiums can soar, mortgage options shrink, and the salability and wealth value of the flat collapse—while the underlying hazard remains in place

Article 2 ECHR: Obligation To Establish a Safe Building System To Protect Life

Against that backdrop sits a deeper constitutional problem: the state’s positive duty under Article 2 of the European Convention on Human Rights to put in place a legal and administrative framework capable of protecting life against known, systemic dangers such as fire in residential buildings. Once government chooses to rely on, endorse or effectively mandate a particular standard as the sole or primary route to satisfying its fire‑safety regime, that standard becomes part of the “building safety system” in Article 2 terms.

PAS 9980 has become, in practice, the de facto guidance for FSO risk assessments of external walls, referenced in central government policy, lender guidance and regulatory expectations. If that guidance contains material errors—particularly errors that encourage limited investigation, normalise combustible constructions as “tolerable”, or tacitly undermine Regulation 7(2)—then the state is on notice that its system may be structurally unsafe and incapable of delivering the level of protection Article 2 requires.

Article 2 does not demand perfection, but it does demand that once grave defects are identified in the mechanisms used to safeguard life, they are not left uncorrected or quietly entrenched. Enshrining, endorsing or giving statutory force to a standard that the state knows contains dangerous flaws would be difficult to reconcile with that obligation: it would look less like a good‑faith attempt to protect residents and more like the codification of a managed risk that falls short of ALARP for reasons of administrative convenience or cost.

If PAS 9980 is to continue as part of the state’s building‑safety architecture, its defects must be acknowledged and remedied, not buried in technical annexes and advisory caveats. If they cannot be remedied, then the Article 2 duty points in only one direction: withdraw it as the primary reference and replace it with a methodology that genuinely reflects the law’s demand for a safe building system to protect life

Common misconceptions and pushback

Some fire engineers argue:

“We’re only responsible for fire safety, not general construction safety.”

Wrong: CDM applies to all health and safety risks, including fire, and the fire engineer’s design decisions affect construction, maintenance and use.

“Our role is to advise on fire strategy; it’s the contractor’s job to manage risk on site.”

Wrong: The contractor’s duty is to manage the risks that are left; the designer’s duty is to eliminate or reduce them first, so that the contractor has less risk to manage.

“We’re not the principal designer, so we don’t have CDM duties.”

Wrong: Every designer has duties under Regulation 11, regardless of whether they are the principal designer or a specialist subcontractor

In short: fire engineers acting as designers under CDM 2015 absolutely do have a first action duty to identify ALL fire hazards and eliminate foreseeable fire risk, and only then move on to consider, apropos what hazard(s) do remain, can they be appropriately managed to reduce the resulting risk ALARP.  Note, it may not necessarily be automatic that the resultant risks may be managed because they may still constitute unacceptable risk; in which case, the design is incompetent and should not proceed further.  If the assessment is that it is possible and practicable to manage the resultant hazards that could not be eliminated, manage what remains; that is not optional, it is a core legal requirement.

Demand Better: Full Verification Now

Leaseholders deserve surgeon-level scrutiny, not bookie's odds. ICM calls for science-led reform—ditch partial sampling, mandate comprehensive openings, and enforce A1-only where practicable. Join the debate at UK-CITF: uk-citf.co.uk.

#BuildingSafety #PAS9980 #GrenfellLegacy #CladdingCrisis #ALARP #FireRisk