A failure investigation provides a more useful starting point than a slogan
Kalamees and colleagues’ 2020 study examined an SPF/polyurea roof over concrete shells at an Estonian museum. The researchers reported major reconstruction needs eight years after construction. Their work included opening the roof at 24 locations and laboratory investigation. It was one unusual cold-climate domed building—not a representative sample of commercial flat roofs.
The installation history described moist concrete, difficulty achieving adhesion, and foam exposed to sunlight before subsequent work. The later investigation found protective-layer defects, water within the assembly, and separation between foam layers. The authors considered water-vapor pressure an important mechanism in the observed blistering.
Separate observation, explanation, and decision
| Published observation | Design question it raises | What it cannot establish |
|---|---|---|
| Concrete appeared dry but installation moisture problems occurred | How will substrate suitability be verified beyond appearance? | That every dry-looking concrete substrate is unsuitable |
| Water entered through damaged interfaces and protection | How do details, continuity, and repair access limit water entry? | A general leak rate for SPF roofs |
| Layer separation and large blisters were investigated | How do moisture, heat, adhesion, and drying interact in this assembly? | That every blister has the same cause |
Rainwater and vapor are different pathways
A rain leak through a detail, water retained during construction, and moisture moving from an occupied space can produce different investigations. The fact that a material resists liquid water does not prove that a complete assembly has an appropriate vapor-control strategy or can dry after becoming wet.
The Gaco example system specification expressly says its described assembly is not recommended for cold-storage or cryogenic structures with constant high vapor drive and directs those applications to technical services. That is a specific boundary, not a statement that all SPF systems are unsuitable for cold storage.
Three building-use scenarios to take to the designer
- Ordinary conditioned commercial space: establish actual interior conditions, existing layers, air leakage paths, and climate rather than assuming a standard interior.
- High-moisture operations: explain process moisture, operating schedules, pressure relationships, and ventilation. A roof-only product decision may miss the cause.
- Cold storage: identify temperature differences and sustained vapor-drive conditions; obtain an assembly explicitly evaluated for the intended use.
These are design-input categories, not recommended layer sequences. Vapor-control location and permeability require assembly-specific evaluation. Generic instructions to “add a vapor barrier” can be misleading without that analysis.
A useful information package for the assessment
Gather indoor temperature/humidity records if available, building-use history, roof layer information, leak timing, previous moisture reports, and proposed changes in operation. Mark what is known, inferred, or unknown. A designer can then determine whether further testing or hygrothermal analysis is warranted.
The moisture-survey guide explains investigation of existing wet materials. This article instead addresses the design questions that determine whether the proposed SPF assembly fits the building. Discuss unresolved conditions during a commercial roof assessment rather than treating a coating as a moisture cure.