When Your Site Shuts Down: How Will Rain Affect Unused Materials?

When Your Site Shuts Down: How Will Rain Affect Unused Materials?

May 8, 2020

Forensic Consulting expert and Managing Director of the Diagnostics Group in Los Angeles / Southern California, Chris Kahanek, discusses site shut down and the effects rain can have on unused materials. 

Building materials and assemblies deteriorate naturally, both through our daily use and by regular exposure to the elements. However, when those same materials are exposed to conditions beyond their design parameters—like when they sit on an inactive construction site waiting for installation—they can degrade severely depending on how they are protected beforehand. In some instances, they can fail completely in the span of a few short days.

Rain and water vapor can intensely damage several major construction elements. Without temporary drainage, elevated horizontal decks will develop ponding that can lead to permanent deflection—or even collapse—and can affect the performance quality of membranes or coatings that have been partially installed.

Most sites manage potential below-grade flooding with dewatering pumps, but every team should consider installing a secondary system if the site is shutting down for a prolonged period—the risk of a heavy rain event increases with time. Similarly, excavation slopes need extra shoring and erosion control measures while construction is halted. We also know that Bentonite-based waterproofing products, are activated by rainwater and other types of below-grade waterproofing are not immune to that exposure either.

Exposed reinforcing steel brings its own set of problems. Usually, most engineers and inspectors require time-consuming removal of rust and other contaminants before placing concrete. Yet, some research shows that a ‘normal’ amount of rust can actually improve the bond between steel and concrete. One glaring exception remains: reinforcement exposed to saltwater in the environment for extended times can collect unsafe levels of salt residue.   

Partially enclosed interiors are at major risk during construction shutdown. Interior floors are unlikely to have slopes, so any ponded water will seep directly into floor and wall materials if left untouched. During rainy seasons, any unfinished structure without proper ventilation will exceed acceptable humidity levels, especially if rainwater seeps through unprotected openings and accumulates.

Of course, mold is a huge threat here too. Interior-grade gypsum board is particularly moisture-sensitive—even a single rainstorm can ruin it. Mold can grow in as little as 48 hours in certain conditions but cleaning visible spots may be enough to save the material. Looking for mold accumulating on inaccessible surfaces can help distinguish areas that need to be replaced.

Water damage due to rainfall during a construction site shutdown can be significant, but with careful planning, the cost can be minimized. Read our full white paper to learn the best methods for combatting rain-related issues during construction shutdown.