The Weather vs. Your Commercial Roof
Mother Nature can pack a real punch. Whether it’s “winter, spring, summer, or fall, all you have to do is call” … your roofing contractor. Now that you’ve got James Taylor and Carole King’s song “You’ve Got a Friend” stuck in your head, here’s what to look for on your roof and when to know it’s time to call in the pros.
Sustained periods of high winds (speeds or gusts more than 40 mph) can wreak havoc on the roof. Aggregate from ballasted roofs can blow off and redistribute, leaving areas of the membrane exposed and vulnerable to the elements. Tree limbs, debris, obsolete equipment, and dislodged roof elements result in punctures, tears, and abrasions as they become airborne and tumble across the field of the roof. Leaks are inevitable.
Some of the worst wind damage is caused by uplift. Roof edges and corners are exposed to tremendous pressure and edge metal damage (e.g. dislodged gutters) is the result. What starts as a small opening allowing wind to penetrate, can have catastrophic results. The entire roof, including the roof deck, can blow off during tropical storms, tornadoes, or anytime the wind uplift is strong enough.
Short periods of heavy rain or even lengthy periods of rain can cause three unfortunate problems for your roof: leaking, ponding, and roof collapse.
Leaks are most likely to occur, when:
- Different plies of material become unbonded.
- Penetration flashings have been compromised (e.g. pitch pocket sealant shrinks and dries out).
- You haven’t completed regular roof inspections and maintenance, which catch problems early.
If your roof lacks sufficient slope or a corroded deck, wet insulation, or heavy rooftop equipment has caused deflection, it’s not uncommon for water to still be present 48-72 hours after a significant amount of rain has fallen. Ponding water can also be caused by clogged roof drains. This water can result in premature aging and shorten your roof’s life. And if enough water accumulates on the roof, it could compromise the integrity of structural members and result in roof collapse.
Despite damage from hail being widespread, it may not be visible. The size of hail, force of its impact, duration of the storm, and the age and condition of the roof system are factors in how much destruction it will cause. Punctures, delamination, indentation, cracking, and substrate damage are common, along with cracked skylights. Schedule an inspection with your roofing contractor who can investigate the full extent of the damage.
If you aren’t performing general preventive maintenance on your roof, the fall leaves may necessitate it.
A collection of leaves and dirt quickly becomes rooftop compost when wet, providing the perfect conditions for wind-borne seeds to sprout. They can clog drains and gutters impeding drainage as well.
As winter gives way to spring, the weather can rise and fall like a roller coaster. Dramatic swings in temperature (i.e. thermal shock) can have a major impact on an older roof membrane nearing or past its intended life. Potential damage to the base of roof membrane penetration flashings and/or exterior roof membrane flashings, as well as pitch pan filler can be expected, along with large splits or tears.
If the roof system has a steep enough slope and/or a low coefficient of friction, avalanching snow is possible. Snow cascading off the roof may not be destructive to the roof system, but it is a hazard for pedestrians walking below. Consider installing a snow retention system.
For low-slope roofs, excessive snow loads and large drifts (uneven load) are concerning, due to the potential for roof collapse. If the structural members are corroded, deteriorated, or damaged, their ability to bare the load is compromised. Older buildings constructed before drifting snow was addressed in building codes in the 1970s-1980s may also be more susceptible. If you’re concerned about the potential for collapse, have a licensed engineer conduct a building inspection and vulnerability assessment.
Have a plan for where the rooftop snow is going to go. Your roofing contractor knows how to work safely on the roof and can remove the snow without causing damage to your roofing system.
The most likely places for ice to form is around roof drains, scuppers, anywhere that ponding water forms, and at the roof eave. Ice dams can occur on both steep and low-slope roofs. When water has nowhere to go because of frozen drains, gutters, and downspouts, ice can back up and break the seal of the roof, as well as damage curbs and flashings. When the snow warms and melts from the bottom, it inevitably results in roof leaks.
On an older roof, insulation may have shifted or shrunk, creating a gap between the exterior and interior wall. The heat loss from the building comes up through the flashing and with no insulation there (and cold outdoor temperatures), condensation occurs.
As warm, humid air rises, the moisture it contains can also condense on the cold underside of the roof assembly. Without ventilation allowing the moisture to escape, water droplets form. Dripping water is most likely when outdoor temperatures hit their high for the day and the sun is out.
Long-term ultraviolet (UV) radiation exposure can result in cracks in the roof system. On modified bitumen and built-up roofs, this can make the roof look like alligator skin. This surface damage happens when oil leaches out of petroleum-based roof systems. If not repaired at the onset, leaking can be widespread and early replacement of the roof will be necessary. Heat and UV can also cause EPDM and modified bitumen roofs to shrink, pulling the flashings at curbs, penetrations, and walls, also resulting in leaks.
Schedule a roof inspection or general preventive maintenance today. Call us at 319.731.4118.