BIA Progress, June – August 2009, Roof Maintenance “Top Side Protection” By Larry Young, Commercial Roofing & Waterproofing
All types of roofing assemblies and coatings require a comprehensive approach, and should not be confused with a thought that roofing repair materials come in a miracle bucket! Roof maintenance really begins with preventative maintenance, which includes having a broad understanding and knowledge of the plethora of roofing products available, and their chemical makeup. Only with this understanding, can the roofing professional select and utilize the proper applications for roof management, maintenance, and preventative maintenance options.
In the early roofing days, petroleum based asphalt and a coal-based pitch were the basic waterproofing products for Hawaii’s low slope and various other vertical roofing applications. The integrated components of asphalt or pa pitch roof provided the waterproofing aspects of the a built-up roofing assembly, while the components of the felt layer performed as the reinforcement for the assembly. The final component, the top aggregate (gravel), acted as the weathering surface and also provides ultraviolet protection.
As technology advanced, refined barrel oil resulted in lower quality and less oil residual to make a good roofing product. However, the advent of SBS (styrene butadiene styrene) and APP (attatic polypropylene), which are asphalt modifiers that enhance the performance of the lesser quality asphalt, roofing products and assemblies were given the ability to exceed performances of the asphalt and pitch.
Although the cost of energy has increased, technology has improved so roof assemblies utilize less asphalt. The increase use of petroleum has helped the industry with thermoplastics, which were generally used for “white” geographic hot zones, and thermosets such as black rubber EPDM single plys for “cool” geographic zones. Their unique chemical makeup has allowed various conditions to weather against things such as animal fats, acid rain, and various chemical residuals.
Today, acrylic coating has now evolved as part of the roofing assembly and can also be used on vertical surfaces. Understanding the makeup of acrylic coating, as well as the other above mentioned products is extremely important as it will determine the application and viability. The main component of an acrylic coating is the base polymer which makes up anywhere from 75 to 80 percent. A good quality acrylic coating is expensive due to its product volume; and fillers whether they be carbon neutral, ash, and other types of additives such as skaeen (a milewcide), and titanium dioxide (a reflective additive) are necessary components that are also expensive.
There may be an ease of application; however, there are limitations and restrictions such as installing in damp or rainy environments which does not allow the polymers in the coating to completely crosslink and bind (generally takes about 2 weeks to cure). There are also limitations to the types of assemblies to which this product can be applied over such as hypalon or pvc single ply, which could result in delamination. The installation of acrylic on pedestrian urethane coating will also at times result in blistering due to the difference in the chemical makeup of the both products.
Acrylic coating is great for waterproofing a surface but it is not able to withstand vehicular and foot traffic such as a parking deck or a roof deck of hospital facilities. There are also acrylic elastomeric maintenance issues to contend with, especially in vertical to horizontal joints, counter flashing slip joints, ponding water, chemical exposures, and more. It is also an excellent way of waterproofing an existing rusted metal roof; however, the rust will continue from the bottom of the sheet and through the acrylic coating waterproofing if it is not sealed from the underside.
The various caulking types that are available (skinning, non-skinning, acrylic, aromatic or aliphatic urethane, neoprene, butyl, etc.) are an integral component of the roofing assemblies including acrylic elastomerics in specific installation requirements. Caulking requires maintenance and resealing due to exposure of the sun’s ultraviolet rays or oxidizing due to rust or the natural metal corrosion process. Many sheet metal flashing and counter-flashing details are a maintenance issue in all assemblies including acrylic elastomeric due to its inherent characteristic of movement from thermal expansion and contraction.
Both preventative roof management and maintenance of various roof assemblies have advanced technologically in their chemical makeup. However, they still require proper and comprehensive training and an understanding of chemical makeup and compatibility issues in its upkeep and maintenance. Extended warranties come with many caveats, and if they are not handles by a properly trained technician, can cause an owner, facilities manager, asset manager, property manger, or condo association to invalidate an otherwise great warranty.