4 FM quick reads on Roofing
1. Identify and fix wet spots on roof
Today's tip is to deal with wet areas on the roof effectively. First, check the roof one of three types of moisture surveys: infrared, nuclear or capacitance.
Infrared surveys measure the heat retained or lost in insulation that has become damp. Ballasted roofs aren't a good candidate for infrared surveys because the rock itself retains a lot of heat, giving potentially false readings. Nuclear moisture surveys measure hydrogen atoms in the roof, meaning that any membrane with a large hydrogen chemical component will send positive readings. Water is a good conductor of electricity, and capacitance surveys measure electricity traveling through the roofing material. This won't work on a roof with wet or ponded areas, and may require modified instruments on EPDM roofs.
If you have 100,000 square feet of roof and four 8-by-10-foot areas are wet, replacing those sections makes sense. But if 30 percent of your roof is wet and it's scattered throughout the roof, the labor to replace all of those sections probably equals the cost of just tearing off the entire roof.
But what if the roof is leaking just after a recent replacement? It's not that farfetched — due to poor design or installation, many roofs experience water leakage soon after construction.
In many instances, water leakage through a roof membrane can go unnoticed because a vapor retarder at the bottom of the roof system captures the water. The captured water absorbs into the insulation, significantly decreasing the thermal value of the insulation and causing premature deterioration of the roof system.
Generally, the membrane does not allow bulk water leakage. Most leaks through a system arise from unreliable detailing.
Roofing system manufacturers provide standard details for perimeter conditions, which typically have the flashing exposed and terminated on the wall surface. They rely on sealants to prevent water infiltration. Manufacturer details typically do not address leaks around the roof system.
For example, in most instances, roof terminations consist of surface-mounted conditions (exposed termination bars or metal flashing) or reglet-set flashing (a small cut in a wall system to insert the metal flashing). In a brick masonry wall, water can bypass the flashing, infiltrate the masonry, and migrate into the insulation. Instead, the design of roof flashing for a masonry wall should incorporate a through-wall flashing that extends through the masonry to capture and divert water out of the wall above the flashing.
2. Condition Monitoring Helps Detect Building Envelope Problems
I'm Steve Schuster, associate editor of Maintenance Solutions magazine. Today's topic discusses building envelopes.
Experienced forensic building envelope consultants know water infiltration is the most common problem for building envelopes on institutional and commercial buildings. While some cladding assemblies might be inherently more vulnerable to damage from water infiltration than others, the problem can affect any cladding system.
Water-infiltration problems commonly take place where cladding systems meet other envelope materials and systems. The challenge for maintenance and engineering managers is to develop maintenance and repair strategies — both proactive and reactive — that effectively target these areas.
Whether a manager employs a proactive or reactive strategy, one good place to start looking for problems is the interfaces of systems and components. Sealant joints might outwardly exhibit failures where the sealant has cracked or split open or has simply aged due to long-term exposure. Adhesive failure occurs when the sealant's bond to the substrate at one or both sides of the joint deteriorates.
But overall, when it comes to minimizing building-envelopes repairs if problems develop, a proactive strategy for the inspection and maintenance of building envelopes is always preferable to a reactive strategy. In situations where a leak is reported and a reactive approach is required, proper diagnosis of the leakage source allows managers to more effectively and appropriately allocate repair funds.
3. How Do Commission Your Roof?
Today's tip, from David Reid and John Wilkins of Gould Evans Architects, is about strategies you should consider when it comes to commissioning your roof.
Most facility managers understand "commissioning" as a strategy that only applies to HVAC systems. But commissioning roof installations is a critical component of a water-tight and energy efficient roof.
Reid and Wilkins suggest three areas to examine when commissioning roofing.
First, look for "weak links" in the integrity of the roofing system, as most of the failures result here. Look at roof terminations, penetrations, flashings at corners, intersections, eaves, curbs and parapets, and drainage systems.
Secondly, especially if you're installing a green roof, but really for any roof, double and triple check that the waterproofing membrane truly is water tight. Perform a leak-detection test appropriate to the type of membrane you've installed. For example, flowing tests flow water continuously over the surface of the waterproofing membrane for a minimum of 24 hours without closing the drains or erecting dams. Electric field vector mapping pinpoints breaches in the roof membrane by tracing the flow of an electric current across the membrane surface.
Thirdly, part of commissioning the roof is creating a plan to protect the membrane until construction is completed and all components - including HVAC, etc. Reid and Wilkins suggest a product called protection board to make sure the roof isn't penetrated or damaged during the rest of the installation or construction process.
4. Roof Replacement Eases Maintenance Woes
I'm Dan Hounsell, editor of Maintenance Solutions magazine. Today's topic is, successful roof replacement. The hailstorm that pummeled the University of Northern Iowa in 2009 did more than uproot hundreds of trees. It also damaged campus buildings and inflicted major damage to the roof of the university's UNI-Dome, a multi-purpose facility on the Cedar Falls, Iowa, campus. The subsequent decision to replace the roof eliminated a long-standing headache for maintenance and operations and brought in a new roofing system that has performed just as intended. The UNI-Dome opened in 1976 and had one unique feature: an inflatable roof. A 1998 storm damaged that roof, which led the installation of a more structured roofing system — a stainless steel, standing-seam system. That roof presented problems throughout its life. "Once we put the standing-seam sheet metal on, it got turned over to me to try to keep it watertight," says Mike Zwanziger, manager of maintenance and operations. "I was working with the local vendor, and every year we'd go up and inspect it. We'd get a report from the UNI-Dome staff about where the leaks were, over what seats, what areas. We were spending, on average, $25,000 a year in an attempt to keep it watertight, and then we'd chase some of these other little leaks throughout the year." But the roof was not simply creating challenges for front-line workers who had to chase the leaks. "We didn't spend a lot of trade man-hours on (roof repairs), but administratively, we spent a lot of time every year trying to trace what was done and what the problems were," Zwanziger says. "It's definitely nice not getting all those calls." The damage from the 2009 storm was a tipping point in the life of the stainless steel standing-seam roof. "Afterwards, when we went up to do an inspection, it looked like someone had taken a baseball bat to the roof, and we had a lot of open seams," Zwanziger says. "At that point, we were able to convince everybody we needed a single-ply roof on it to keep it watertight." The new system also has benefited the maintenance and operations department. "The occupants have been very happy it's not raining inside the dome," he says. "They used to be out there with mops trying to clean up the water or moving people during games so they wouldn't get dripped on. That's probably been the biggest benefit of all."
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