Damage Caused by Drainage Issues
In a school investigation in Superior Arizona, Steve Klingler and team were asked to review several construction issues, among them the cause of damages to the main structure in the form of vertical cracks and separations at the west-facing exterior Concrete Masonry Unit (CMU) wall of the gymnasium. We were called in to determine if the damage was the result of poor workmanship and/or design flaws.
In any forensic investigation, we first attempt to identify apparent patterns of distress, and upon arrival at this site, we recognized clear issues with drainage for the property. Past rainstorms had directed surface water into the school entrance on the north and repeated occurrences had required the school to attempt repairs to the roof drainage discharge and make corrections to the curb and pavement design.
As our evaluation progressed, we did find design shortcomings; however ultimately we discovered that the school had been constructed over a moderately large tributary wash. This wash, which had once extended from the eastern portion of the property and drained to the lower sections to the west, had been simply backfilled to accommodate construction of the building pad, without establishing a clear path for drainage. Lacking a defined path to resemble something close to the original drainage flow, surface water repeatedly attempted passage through the footprint of the school, building up and impacting the west building line and foundation for the gymnasium which sat at the lowest point. The pressure from this added moisture in the soil had moved the foundation to such an extent that large separations in the CMU had dangerously affected the structural integrity of the wall and damaged some of the beam pockets supporting an adjoining roof structure.
As it turns out, this matter had more to do with poor site planning than design or construction flaws. Many issues in Arizona are a result of poor planning and consideration for drainage, which is a critical factor to incorporate into any building design and a requirement to maintain natural drainage tributaries in rural locations. Cutting off or redirecting the flow of surface drainage forces the water to find a new route, which may contribute to a consolidated flow and ultimately result in flooding and accelerated erosion. And in the case of this school, it contributed directly and negatively to alter the foundation soils.
see also:
The Case of the Roof Leak that Wasn't
Roof Collapse
Interstitial Condensation
Damage Caused by Drainage Issues
"Punch List" Inspection Prevents Disaster
The Leaky Roof and Pitted Clay Tiles: A Closer Look
