4 FM quick reads on Roofing
1. 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.
How to Choose Best Single-Ply Roofing System
Before a facility executive begins weighing the question of which single-ply system to use, it is important to ask whether the building is suited for a single-ply membrane. "One size fits all" is as misleading for roofing as it is for clothing. Here are some situations where a single-ply membrane is appropriate when:
- weight is a consideration
- some movement may be expected in the building structure
- recovering an existing membrane
- the building is wide open and large panels can be used
- reroofing structural standing seam metal roof assemblies
- roofing in cold weather (with some precautions)
- installing a green roof
- a light-colored system is desired
Times when a facility executive may want to consider other options include:
- when vandalism or puncture-abuse is a factor
- when there is a limited number of local approved applicators
- when there is a chemical incompatibility between the existing roof and the proposed re-cover membrane
- when climatic or environmental conditions are not appropriate
- where insurance considerations favor other types of systems
- where installation is over lightweight insulating concrete decks
- where local building code officials prohibit use of particular types of membranes
Except for the last item, none of the above are hard and fast rules. They are issues that need to be addressed before choosing a particular type of roof system, regardless of whether it is asphalt-based, thermoplastic or synthetic rubber.
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.
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.