When Your Site Shuts Down: How Does UV Radiation Affect Unused Materials?

When Your Site Shuts Down: How Does UV Radiation Affect Unused Materials?

August 3, 2020

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

Building materials and assemblies deteriorate naturally, both through daily use and by regular exposure to the elements. When materials are exposed to conditions beyond their design parameters—especially when they sit on an inactive construction site waiting for installation or are already installed without any protection—they can degrade rapidly, depending on the type of protection that is implemented.

UV radiation—mainly UV-A with a wavelength in the range of 320 nm up to 400 nm—constitutes the major portion of the radiation that reaches the earth’s surface. When exposed continuously to UV radiation, various building components may experience detrimental effects. These include air and weather barriers, traffic coatings, below grade waterproofing systems, roofing membranes, and concrete sealers.

Air and weather barriers can be either sheet-applied or fluid-applied products. When subjected to UV radiation, internal hydrocarbons undergo chemical decomposition, releasing carbon dioxide and water. In some scenarios, the team may opt to modify storage for these materials already on site, rather than obtaining new products that are more UV resistant. In such cases, the UV stability can be increased by covering the material with compatible, felt products from the same or a different manufacturer, or by using UV resistant paints, tapes, or other air barrier products on top of it.

Traffic coating for vehicular surfaces—also called traffic topping— is considered an elastomeric waterproofing membrane. Traffic-coating systems are typically comprised of a base coat, intermediate coat (some with aggregate), and topcoat (with aggregate for slip resistance).

The base coat provides the primary waterproofing function and has lower tensile strength to allow for crack-bridging flexibility. The intermediate coat and the topcoat layers have aliphatic material properties that have higher tensile strength, wear capability, UV-exposure capability, and impact resistance. The base coat layer’s UV protection relies solely on the intermediate and topcoat layers.

Below grade waterproofing is usually designed to last the entire life of the structure. Most below grade waterproofing products contain hydrocarbons and—with exposure to UV radiation—oxidation and breakdown of these hydrocarbons will occur, thereby decreasing the life expectancy of any or all the compounds. When construction shuts down, cover up the waterproofing membrane, either by casting concrete or by using a protection board or drainage board to cover the exposed membrane until construction resumes. Membranes already exposed to UV may need to be removed and replaced if the exposure limit was exceeded.

Common roofing membranes include PVC, EPDM, SBS, APP, and other asphaltic membranes. The basis of degradation of these products is dependent on the exposure of hydrocarbons to varying wavelengths of UV radiation, molecular decomposition, and oxidation processes. Polymethyl Methacrylate (PMMA) waterproofing products are best suited for long term exposure to UV because many PMMA products state allowable exposures time to be around 20 years or more.

Concrete coatings and sealers include the following: Epoxies, Polyurethanes, Acrylics, Silanes, and Siloxanes. As discussed earlier, epoxies are known to be highly UV-unstable when compared to polyurethanes or acrylics. Acrylics are known to be the most UV-stable compounds, taking a long period of time to decompose under UV radiation. The silanes and siloxanes are known to be highly UV-stable and can be used for outdoor applications.

Ultraviolet radiation can cause significant damage to installed products, requiring extra care to protect materials during an extended construction site shutdown. With a relatively small investment, construction restart costs can be minimized by installing temporary protective membranes and coatings or choosing UV-stable products from the outset.

Read our full white paper to learn the best methods for combatting UV-related issues during construction shutdown.

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