Project Type: Evaluation and Design
The Vital Structure:
Mechanical Roof Replacement
Issue
Vital Structures was retained to perform an evaluation of the existing EPDM roofs of the main building. The facilities manager specifically noted that after a rooftop mechanical equipment upgrade project, substantial leaks occurred into the mechanical penthouse below.
Diagnosis
The area of concern is congested with mechanical equipment for the pharmaceutical laboratory and office space. Vital Structures performed an evaluation of the existing EPDM roof system; including review of original design documents, review of previous infrared roof scan documentation, exploratory test cuts, and limited peer review of the mechanical upgrade project. The following conditions were noted by Vital Structures:
- Ponding around new/congested equipment areas.
- 80+ areas of mechanical duct supports mechanically fastened (screwed) through the roof membrane
- Saturated roof assemblies, leading to poor thermal insulation performance.
- Standing water under roof membrane; with submerged wood blocking.
- Un-sealed roof penetrations.
- Abandoned-in-place sleepers, blocking and mechanical/electrical penetrations.
- Un-sealed HVAC systems under negative pressure.
- Roof membrane punctures and insufficient slope-to-drain due to saturating and crushing of the roof assembly.
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Solution
Vital Structures prepared a roof evaluation report with evaluation drawings, analysis of IEBC-2015 re-roofing provisions, general recommendations and preliminary budget estimates for the recommended scope of work. The evaluation report and proposed design included the following:
- Full roof replacement with R-30 roof assembly, improved slope-to-drain, and crickets at roof drainage obstructions.
- New through-wall flashings and masonry coating at rising walls.
- Modification of HVAC duct supports to eliminate fastener punctures through the roof membrane.
- Replacement of deteriorated wood blocking with insulated metal curb bases.
- New roof overflow drainage system.
- Replacement of at EPDM-wall penetration flashings.
- New roof access doors with increased flashing heights.
Result
Due to the roof being enclosed on four (4) sides, the new overflow drainage system will prevent potential ponding and water infiltration in the event of a primary roof drain failure. The proposed roof system will improve drainage by providing a slope of ¼” per linear foot, and by providing crickets to prevent ponding around mechanical units. New roof access doors will facilitate increased flashing heights and improved the slope-to-drain. Structural modifications of the HVAC duct supports will allow the structural members to be anchored to the roof deck, and will allow the members to be flashed with a conventional EPDM flashing boot, eliminating the fasteners through the roof membrane. Modification of the masonry through-wall flashing will provide increased flashing heights and improved slope-to-drain. New protective masonry coating will control moisture infiltration, deterioration and freeze-thaw cyclic effects on the masonry penthouse walls.
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