Water Ingress in Commercial Cladding Systems

What Is Water Ingress?

Water ingress through commercial cladding is the penetration of rainwater or moisture into the building interior through the cladding envelope. It is the highest-cost outcome of deferred cladding maintenance: by the time visible internal evidence appears — damp patches, water on floors, damage to stored goods or racking — penetration has typically been occurring for months or years. The internal evidence rarely identifies the external entry point, which may be metres away depending on the internal drainage path.

Why Does Water Ingress Occur?

Water ingress occurs when the continuity of the waterproof envelope is breached. On commercial cladding, this breach can occur at multiple points:

• Failed lap sealant: The most common cause on profiled steel sheet systems. Sheet laps rely on a continuous sealant bead to prevent water penetrating the overlap. Original butyl or foam sealants have a finite service life — typically 15–25 years. Once sealant has hardened, cracked or compressed to zero thickness, water tracks through the lap under wind pressure.
• Failed ridge and capping sealants: Ridge cappings and perimeter flashings rely on mastic sealants at their joints and junctions. These degrade over time in the same way as lap sealants.
• Cut edge perforation: Where cut edge corrosion has progressed to sheet perforation, a through-hole creates a direct water ingress pathway that cannot be sealed by surface treatment alone.
• Corroded fixings: Self-drilling fixings with failed neoprene washers, or fixings where the steel shank has corroded, allow water to track down the fixing shank into the building. This is a frequent cause of localised damp patches below fixing lines.
• Failed composite panel joints: On composite panel buildings, joint sealants or factory jointing compounds that have degraded create ingress points at the panel junctions.
• Design deficiencies: On some older buildings, original design omissions — insufficient lap dimensions, missing flashings, inadequate drip details — create ingress vulnerabilities that no maintenance programme can resolve without physical alteration.

How Is It Assessed?

Assessment begins externally — a systematic inspection of all junctions, laps, cappings, fixings and panel joints to identify potential ingress routes. On buildings where the ingress point is unclear, a targeted water test (controlled wetting of specific external areas while observing internal response) can help isolate the source. On larger buildings, this is a systematic process that requires close inspection from access equipment — ground-level observation will not identify failed lap sealant or fixing condition.

Internal evidence — damp location, direction of water flow from damp origin, pattern of reoccurrence — provides diagnostic clues. Water mapping (recording all internal evidence and correlating it with external features on a building plan) is the most reliable approach for complex multi-source ingress cases.

When Refurbishment May Be Suitable

Coating-based refurbishment addresses water ingress where the ingress route is through surface coating failure on the cladding face, or where sealant renewal is incorporated alongside the coating programme. On a building where the primary ingress source is failed lap sealant or capping sealant, a refurbishment programme that includes sealant renewal at all laps and junctions before the coating system is applied will resolve both the ingress and the coating deterioration in a single programme.

When Refurbishment May Not Be Suitable

Coating treatment cannot address water ingress caused by: perforated sheets (mechanical replacement required); structural fixing failure where the fixing shank has corroded through (fixing replacement required); design deficiencies requiring physical modification to lap dimensions or flashing configuration; or delaminated composite panel joints requiring panel replacement.

When Replacement May Be More Appropriate

Where the primary ingress route is through multiple perforated sheets, systematic fixing failure, or design deficiencies that cannot be economically remediated, the cost of mechanical repairs may approach or exceed the cost of replacement. An assessment that maps the full extent of ingress routes provides the data needed to make this comparison accurately.

Systems Commonly Considered

Rocathaan Hotspray PA 260-FR and ProFix are the primary systems for ingress-related refurbishment. Rocathaan Hotspray PA 260-FR's enhanced film build provides superior weather resistance on buildings with demanding water exposure. ProFix addresses cut edge corrosion that, if untreated, would create new ingress routes after the top coat is applied. On composite panel buildings, sealant renewal at joints is a separate trade scope that precedes the coating programme.

Common Mistakes

• Treating the internal manifestation (damp patches, water staining) rather than identifying and treating the external source.
• Applying coating over a building with unresolved sealant failure at laps — the coating seals the flat sheet face but not the lap joint beneath it.
• Not including fixing inspection in the scope — failed fixings are a common ingress route that is invisible until the system is examined at close range.
• Assuming that a new coating will seal the building without confirming what the ingress route actually is.
• Not mapping internal evidence before starting external works — the pattern of internal damp provides diagnostic information that guides the external inspection.