4 FM quick reads on Roofing
1. Plan Re-Coating Schedule to Help Maintain Roof
Over the longer term, it makes sense to plan a re-coating schedule that calls for a new coating every eight to 12 years, one expert says. "Don't wait for it to start cracking and peeling." He adds that many roofs can be re-coated for the service life of a building. "As long as the base coating is solidly attached, the next coat can be applied and will look good."
While applying a roof coating should be less expensive than re-roofing, that doesn't mean it makes sense to go as cheaply as possible. Before considering a low-cost operator, find out why the company is able to offer a lower cost, another expert advises.
"How was their competitive advantage derived?" he says. If it's simply from using an inferior product, it's probably not worth it. An inexpensive coating that lasts a fraction of the time or requires more applications than other coatings likely will end up costing more time, money, and aggravation overall.
"There are differences among producers regarding the suggested coverage rate of their coatings," says another manufacturer representative. "This factors into cost of material as well as, more importantly, the cost of labor." A less expensive coating may not have the hiding power of a higher quality coating, and so will require multiple coats. And lower-quality resins may be quicker to crack or lose their adhesive properties, so that the coating erodes more rapidly.
"The cost of labor is the largest component of cost in construction," the manufacturer rep says. It doesn't make sense to spend less on a product that is lower quality only to have to recoat the roof more frequently — which boosts labor costs. "Over time this is more costly to the building owner," he adds.
Many local code authorities require roof coatings to meet ASTM standards for such attributes as tensile strength and permeability, as well as fire resistance. But that's not the case everywhere.
2. Big Top: Reroofing California's State Capitol
Every single step, it seems, presented a challenge when it came to reroofing the California State Capitol building in Sacramento — scheduling, security, and maybe the most maddening challenge of all, surprises. Throw in the chaos created by the building's 3,000 occupants — including a state legislature and its committees in and out of meetings — as well as 750,000 visitors annually, and the entire process might even seem overwhelming.
For all its challenges and surprises, one main goal of the reroofing project on the California state capitol building focused on a problem every maintenance and engineering manager knows all too well — leaks.
"It was leaking profusely," says John Manning, the building's chief engineer, referring to the 98,000-square-foot surface that included several types of roofing systems and nearly 30 different sections — some sloped, others flat.
"There are actually two buildings that comprise the current state capitol," Manning says. "The first completed construction in 1869. Then in the late 1940s, a second building was built directly next to it, so it becomes one building. That finished construction in 1951."
"The roof had been on the capitol for more than 20 years, and there were leakage problems, and it was at the end of its life," says Marilyn Nelson, project manager with the state's department of general services. "When we replaced it, there were several roofing systems down below it, and we had some hazmat issues. We had to do all the demolition at night, and we reroofed it during the day. Because it is such a large roof, we had to do it in sections and phases."
The new roof is a PVC system with 10-foot-wide panels.
"We chose it because it was long-lasting and durable," Nelson says. "As you can imagine, you don't want to reroof this capitol very often. It also had a decent solar-reflective index. And it has fewer seams because of the 10-foot-wide panels."
3. How to Avoid Moisture Issues to Prevent Roofing Installation Problems
Once managers have settled on the type of single-ply system to install, the next step is ensuring that installation occurs as intended during design to prevent problems, such as the introduction of moisture.
"If the single-ply system is not installed correctly, then you run the risk of high maintenance costs by not only having to repair the membrane but also having increased risks of having to replace the underlying components sooner than with multi-ply systems because you do not have the added protection for additional layers," says Amrish Patel with Simpson, Gumpertz, and Heger. "If you don't address moisture issues within the substrate at the beginning of the project, maintain proper adhesive application, proper flashing details or proper membrane application, you may be constantly patching or prematurely replacing the roofing system.
"With single-ply membranes, your primary mode of failure occurs at the seams of the membranes. If a membrane seam has failed, you've got immediate water penetration into the roofing system, so the seams really need to be inspected to ensure they are installed properly, for example, whether they are heat-welded seams with a PVC or TPO system or adhered seams with an EPDM system."
Patel also warns managers to beware of moisture in the existing roof's substrate.
"If you install an adhered roofing system, that moisture is eventually going to start to cause debonding of the insulation and cover board and possibly of the roofing membrane," he says. "And through wind-uplift cycles, you're going to lose the adhesion of the roofing system. That often gets overlooked."
4. How Vegetative Roofs Extend Service Life
Plants, soil, and covered components of the system offer protection from the elements, including degradation by the sun's UV rays. By protecting the membrane, a vegetative roof can minimize cracks and splits due to the thermal cycle. In some areas of the country, a roof membrane surface that is exposed to the sun may reach temperatures above 160 degrees Fahrenheit during the day and drop below freezing that night. The resulting expansion and contraction wreaks havoc on the membrane. But with a vegetative roof, this can be minimized, reducing or even eliminating one of the main causes of roof leaks.
As much as a 200-300 percent extension of roof membrane service life may be achieved with the use of vegetative roofing. This is backed by the availability of manufacturers' warranties for as long as 30 years for the entire roofing system. In some cases, the warranties can even include the removal and replanting of the vegetation if a leak needs to be repaired.
In addition, using a vegetative roof over the membrane can reduce the risk of hail or wind damage to roofs. Airborne debris such as tree limbs and other windblown items is also much less likely to penetrate the roof during a storm.
Damage caused by human error is another common cause of roof leaks. A maintenance technician may have an object such as a rock or a fastener screw on a shoe bottom and cause damage or even punctures to the roof as they walk across it. Even when walkways are provided and clearly marked, workers don't always follow the rules.
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