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DCD Magazine

Verifying the Quality of Your Roof Investment
By: Melissa Rus

After months of research, careful selection and completion of the bidding process, the purchase order for your new roof system has finally been issued. Now a simple question comes to your mind: “How can I be certain the materials being delivered are equal to what was specified?”

How Certificates of Analysis Work
The answer is simple, but all too rarely recognized - request a certificate of analysis from your roofing materials supplier. A certificate of analysis is a document issued by the manufacturer summarizing the performance test results for the specific lot of material shipped to the customer. It provides assurance that the roofing materials delivered to your job site meet the performance properties called for in your product specification. This documentation also provides batch trace ability should a material issue or defect be identified in the field.

Starting at the raw material level, to ensure trace ability, material certificates of analysis are relied upon heavily in quality-system-approved manufacturing environments, where they are required to accompany all materials utilized in the processing of finished goods. Whether it is the thickness of the metal coil used to create your metal roofing panel, or the softening point and penetration of the base asphalt used for your SBS modified roofing sheets, each raw material must meet the necessary specification or the finished material could be rejected at final quality inspection.

Manufacturers establish specifications with their suppliers and institute protocols to ensure every shipment meets the performance properties necessary to produce quality finished goods. When materials are delivered to the plant, quality control departments review the certificate of analysis and perform quality checks. If a material is found to be out of specification, prompt action is taken to return the material to the supplier or to identify corrective action for nonconformance. Additionally, should a problem arise in the field with a finished roofing product, the manufacturer will be able to review data from every raw material used in manufacturing your finished product. This data can then be used to help determine the root cause of a product failure.

Final quality inspection takes place after a manufacturer produces their products. Ultimately, as the customer, this is the information that is most important to you. In selecting products for your roof, you, your architect, and/or roof consultant have selected specific materials based on design criteria. Quality checks by the manufacturer ensure that materials provided meet specific design requirements.

How to Use the Info Provided
Buzz words in today’s marketplace include sustainable, recycled content, highly reflective, high strength, 100 percent solids, and VOC compliant. As the customer, you typically have “to take their word for it” that the product you purchased complies with what the manufacturer is advertising.

The manufacturer ultimately takes on the responsibility of ensuring that the products they are supplying meet the minimum performance characteristics as listed in their product specifications. These product specifications are typically established based on test results obtained from independent test agencies. Once the specifications have been established, it is usually the manufacturer of the product who is performing the tests listed on the certificate of analysis.

…for Membranes
For example when producing a modified roofing membrane, the end product is tested according to ASTM material specifications. For modified bituminous sheet materials the specific tests should include membrane thickness, low temperature flexibility, load strain properties, and compound stability. The load strain properties are determined by the reinforcement used to construct the membrane during manufacturing. However, once coated with the asphalt and polymer compound, you are unable to identify what the reinforcement is.

Two other important tests include low temperature flex and compound stability. These test values will confirm that the products were properly mixed with the required polymer loadings. Poor polymer dispersion or low loadings of polymer will yield low test values for low temperature flex and compound stability.

…for Scrims
There is a wide range of typical reinforcements, from polyester, fiberglass, and combinations that can be supplied as mats or scrims ranging from low to very high tensile strengths. The load strain properties listed on the certificate of analysis will allow you to confirm that the mat you chose was used to form the products you received.

…for Coatings
For coatings, typical tests may include solids, density, VOC calculations, reflectance and viscosity. These tests are all covered under ASTM specifications as well. As a customer this data is important in ensuring that the products you have received actually meet the local (VOC) volatile organic content limits or reflectance minimums for your specific location. As states and municipalities continue to set limits for VOC and reflectance, it is imperative that you receive documentation that the products on your job site meet the necessary limits.

Another important value is the product viscosity; this data can be helpful to the contractor during product application. Manufacturers typically formulate products to fall in a certain viscosity range. If the product is supplied outside the normal range, there can be improper application rates during installation, which can result in product failure.

In conclusion, requiring your materials manufacturer to submit a certificate of analysis for each lot of material delivered to your job site allows you to be certain that you are receiving the quality product that you specified and paid for, providing reassurance that the completed roof will realize the performance outcomes anticipated.

About the author: With a background in the development of SBS modified asphalt roof membranes, roof coatings, and fabric reinforcements, as well as active involvement in industry trade associations such as ASTM, CRRC and RCMA, Melissa Rus has been part of Garland's research and development team since 1994. She holds a bachelor's degree in Biology from John Carroll University.

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