Forensic Assessment of Roof Structure Following Deflagration Event

Situation

A deflagration event occurred within a single unit of a multi-unit, one-storey industrial building in Toronto. The incident resulted in overpressure conditions within the affected unit, leading to displacement of an overhead door and lateral movement of masonry demising walls. While glazing remained intact, visible structural damage was observed within the roof framing system.

Concerns were raised regarding the structural integrity of the open web steel roof joists supporting the roof over the affected area, and whether the damaged members could be safely repaired or required replacement.

Engineering Scope

Engaged to perform a forensic structural assessment of the roof framing system within the affected unit, with a focus on evaluating the condition and structural reliability of the open web steel joists subjected to overpressure effects.

The scope included site inspection, documentation of observed damage, assessment of member behavior and connection integrity, and evaluation of the feasibility of reinforcement or repair of the affected structural elements.

Key Engineering Considerations

• Extent and nature of overpressure-induced structural damage

• Localized distortion of open web steel roof joists

• Chord deformation and web member distress

• Condition of joist connections to supporting elements

• Interaction between roof framing and displaced masonry walls

• Reliability of damaged members under gravity and service loads

• Limitations of repair versus replacement for compromised joist systems

Outcome

The assessment identified significant structural damage to multiple open web steel roof joists, including chord deformation and connection distress, as well as cracking and displacement of adjacent masonry elements. Based on the extent of observed damage, the affected joists were determined to be unreliable for continued service under design loading conditions.

A detailed forensic engineering report was prepared documenting observations, damage mechanisms, and structural implications, along with recommendations regarding the suitability of repair versus replacement. The findings provided clear technical guidance to support decision-making related to structural remediation and ongoing safety considerations.

Post-incident assessments involving overpressure events and structural damage require evaluation by an experienced structural engineer in Toronto to determine residual capacity, safety, and appropriate remediation measures.

Related Engineering Services

• Forensic Structural Engineering

• Structural Damage and Failure Assessment

• Industrial Building Structural Evaluation

• Post-Incident Structural Investigations