4 FM quick reads on Roofing
1. How to repair a wet roof deck
Wet roof decks simply can't be ignored. Recovering a wet roof deck won't make the problem go away. That's because recovering a roof deck will likely only cause the roof to blister, or cause other serious problems that won't be covered by a warranty.
Here's how to tackle a wet roof deck the right way. First, identify wet areas in the roof. To do so, one of three types of moisture surveys should be completed: infrared, nuclear or capacitance. None of these actually measure moisture. Instead, they measure the effect moisture has within the roofing materials.
For best results, match the type of moisture scan with your roof since each moisture scan works differently. Infrared surveys measure the heat retained or lost in insulation that has become damp. Ballasted roofs aren't good candidates 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.
The amount of moisture found in the roof, if any, may dictate the choice of whether to recover or replace. The more areas of moisture found, the more expensive it will be to replace those areas.
2. What You Need To Know About Flat Roof Coatings
Flat roof coatings can be a good investment for many facilities. A flat roof coating can extend the life of a roof because it lowers the roof temperature. It can also lead to additional energy savings as the temperature is reduced.
Still, because there are so many different types of roofs in use today, specifying a flat roof coating isn't easy. Different substrates require different coatings. A coating's adhesion might depend as much on the substrate's characteristics as on the coating type. In general, it is more difficult for coatings to adhere to hard, smooth, chemically inert surfaces and easier on rough, irregular, chemically active surfaces.
A coating's adhesion to a substrate often improves when the installers put down a primer or base coat. Coatings manufacturers recommend certain primers or base coats for managers trying to match a specific topcoat with a specific substrate. Managers should use only the base coat or primer specified by the coating's manufacturer.
With the introduction of roof membranes such as ethylene propylene diene monomer (EPDM), polyvinyl chloride (PVC), thermal polyolefin (TPO), Hypalon, modified bitumen, and built-up roofing, manufacturers have developed a variety of roof coatings to address multiple substrates with different adhesion and weathering characteristics.
Managers can specify asphaltic and tar-based coatings for use with coal-tar-pitch built-up roof systems. Non-asphaltic coatings, including urethanes, acrylics, and polyureas, are most commonly used on single-ply systems.
Each of these coatings has different cost and performance factors. Due to variations in coating formulations, a manager should work closely with a roof consultant and the manufacturer to make sure they specify the right coating for the roof substrate and that workers perform the correct repairs before applying the coating. Manufacturer representatives and product data sheets also can assist in specifying coatings.
3. Three Places to check for Leaks
Roof leaks are a major headache to fix. The good news is that some leaks are predictable — especially as the roof ages. By identifying areas that are prone to developing problems, steps can be taken that will prevent roof problems cost effectively.
Look For Roof Leaks Near Penetrations
Flashings and sealants at penetrations through the roof membrane are common trouble spots. Typically in single-ply roofing systems, penetration flashings are the same material as the roof membrane and are bonded to the field membrane. Inspect the laps, seams and sealants at these locations regularly.
Roof Leaks On The Perimeter
Leaks occur near roof edges because of the transition from flexible membrane flashings to inflexible sheet-metal flashings. Technicians should ensure that sheet-metal laps shed water, and they should inspect the sealants at these locations regularly.
Condensation And Roof Leaks
Sometimes, a roof might appear to leak in January when the temperature dips below freezing, but the roof might not be leaking. What happens is condensation is created when the warm, moist interior air inside the building contacts cold surfaces or when cold air leaks through the building's exterior skin.
4. Keys to Ensuring Successful Rooftop PV System
The first step in the successful installation of a rooftop photovoltaic (PV) system is to ensure the underlying roofing system is compatible with the intended PV system or that it can be upgraded for use with a PV system. For a rooftop PV system, the process of integrated design — having all parties involved with a project, including maintenance and engineering, at the design table — requires knowledge of both the roofing and PV industries.
Having the right people at the design table helps to create a proper path from design to installation to maintenance. To ensure a successful design, managers need to:
- make sure the roofing system will provide at least 20 additional years of useful service
- specify a cover board as a substrate for the roofing membrane in order to prevent damage and to protect the energy-efficiency properties of the roof insulation
- match the roof membrane's thickness and proven performance to the required service life of the PV system
- use construction details that are well established and meet the manufacturer's requirements
- elevate framing and conduits above the roof surface to promote drainage, which considerably reduces the potential for leaks
- design penetrations with round framing so flashing installations are more effectively and efficiently installed
- install sacrificial membranes or walkways at critical traffic locations
- provide additional membrane layers or coatings at flashings to increase durability
- engage qualified professionals during the design and planning phase to ensure compliance with all building codes and safety regulations
- make sure the rooftop PV system installation does not compromise the roofing system's warranty
- make sure that the roofing system's manufacturer has accepted all PV system details — especially attachments and penetrations — if not during the design stage, at least prior to starting the PV installation on the rooftop.
The manager's overall goal is to make sure the rooftop PV system will do more than just survive. It also should help ensure continuous building operations.
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