In recent articles we talked about delamination of roof membranes where attached to oxidizing ferrous metals. Today we look closely at a few real examples from flat or low-slope roofs out in the field.
Rusty metal, single-ply, or modern membranes can lead to delamination when they are attached to metal at penetrations or flashings due to a chemical process known as oxidation. Oxidation occurs when iron molecules in the metal react with oxygen (O2) and water molecules (H2O) in the presence of moisture.
This process, of rusting, happens on a chemical level by the formation of Iron Oxide (Rust). Iron is abundantly available in most places on earth, it’s present right in the dirt outside, in most locations. but that particular form of iron is iron oxide. iron oxide actually goes through a pretty elaborate process of industrial manufacturing to become either iron ore or or steel as is commonly used in the production of most consumer or building construction type materials.
The formation of iron oxide, or rust, is a new compound that is less stable and more porous compared to the original metal. This compound has a tendency to flake off or become brittle over time.
Rust is a brittle and less cohesive material compared to the original metal. When roofing membranes or sealants are attached to rusted metal surfaces, they may adhere initially. However, over time, the rusted metal’s decreased cohesion and adhesion properties can lead to a separation between the roofing material and the metal.
Delamination refers to the separation of layers, and in the context of roofing, it means the roofing membrane detaches from the rusted metal surface. The chemical composition of rust makes it less adhesive, causing the roofing material to lose its bond with the metal.
When delamination occurs, it creates gaps or openings between the roofing material and the metal surface. These gaps can allow water to penetrate beneath the roofing membrane, leading to leaks and water damage in the roofing system.
To prevent delamination due to rusting, it’s important to maintain the integrity of the metal surface by addressing rust and corrosion issues promptly. Protective coatings, regular inspections, and maintenance can help extend the lifespan of the metal and prevent the chemical process of oxidation from causing adhesion and cohesion failures in roofing systems.
Routine maintenance such as the type needed as shown in the areas of the photos below where there is rusting near the connection point between a roof membrane boot and a substrate penetrating pipe, can be the difference between a properly functioning roof and a leaking roof In this type of circumstance, the rusting metal must be chemically treated, for chemical conversion, or physically removed with abrasion or mechanical means.
Smart and proactive replacement, construction, upkeep and maintenance of low slope roof and mansard roof systems requires an enthusiastic interest and understanding of historical methodologies, waterproofing principles, and building science. Here in Washington DC, historic and modern residential and commercial buildings are extremely expensive and the roof and related systems provide the shield that preserves the building.
We encourage all of our clients, and all readers of this article and to our blog in general, to prioritize the value of quality construction and building maintenance, and develop a relationship with our company. You can learn a lot more on our blog. Feel free to check it out. If you have questions about the roof and related systems of your building in Washington DC, contact us or fill out the webform below and drop us a line. We will be in touch if we can help.
