roof and pavement consultants

Observations From The Field: Improper Design and Installation

Service: Design Review

Issue: Benchmark was asked to review design documents in preparation for destructive testing of a recently constructed roof system on a new building at a paper manufacturing facility.  The design of the parapet wall and associated cavity did not include a vapor retarder or seal.  Due to high heat and humidity generated by production activities on the interior, a vapor retarder/seal is required to prevent moisture migration and condensation within the wall cavity.

Solution: Proper design and/or peer review of the construction documents prior to installation would have prevented the detail from lacking this key component. Additionally, hiring an unbiased third-party consultant to observe roof installation and advocate for the Owner would have helped avoid this situation. Reportedly, the condition was discussed during installation and the contractor opted to complete the detail as specified for cost saving reasons. The Owner now must rectify the condition by dismantling the wall, removing all wet components, installing a vapor retarder/seal, and replacing components.

Possible Impact: The direct result of the absence of a vapor retarder/seal at this critical juncture led to moisture migration and condensation within the wall cavity, saturated insulation, decreased R-value, condensation collecting on/in the interior walls, corroded fasteners, deteriorated plywood, unadhered flashings, organic growth, formation of ice on the building exterior which has created an unsafe condition due to falling ice, and ultimately water intrusion into the one-year-old roof and building. Left as is, this condition will promote early roof failure and result in significant expense to the owner.

Rockwool batt insulation is saturated and sagged. Note organic growth, surface rust, and steam emanating from the opened wall. Close-up of plywood. Note organic growth and corroded fastener.

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