A flat roof leak around an HVAC unit doesn’t necessarily mean the roof itself has failed. In fact, many “roof leaks” actually begin inside the HVAC system. From condensation to dirty air filters, there are many possible culprits of leaks inside the building. Determining the exact nature of a roofing or HVAC-related issue from the start can help Greater Toronto Area building owners address problems faster, minimize disruption, and avoid unnecessary repair costs.
Rooftop HVAC units require multiple roof penetrations, flashing details, electrical connections, condensate drains, and service access. Because so many roofing and mechanical components come together in one location, HVAC units are one of the most common areas where leaks develop on commercial flat roofs.
Calling a trusted local commercial roofer to uncover the root cause is the first step.
Not Every Roof Leak Around an HVAC Unit Is a Roofing Problem
Because water follows the path of least resistance, leaks may appear inside the building, well away from the actual source. If you’re seeing a water stain near a rooftop HVAC unit, don’t assume a problem with the roof itself is to blame. It could actually stem from an HVAC issue.
That’s why roofing contractors and HVAC technicians should work together to identify the true source of the leak. There could be any number of problems causing the leak in question, from the HVAC system to the commercial roof membrane and flashing – or even a combination. Knowing where the leak originated can prevent unnecessary repairs and further water damage.
Common Seasonal HVAC Problems That Cause Roof Leaks
Each season brings unique challenges to roofs and the HVAC units that sit atop them. Here’s a look at the common summer and winter HVAC problems that cause roof leaks.
- Condensation From Constant AC Operation: During the summer, air conditioning units produce large amounts of condensate, especially during periods of heavy use. If the drainage system becomes clogged, overwhelmed, or improperly configured, excess water can overflow.
- Dirty Air Filters Can Cause Frozen Evaporator Coils: Dirty air filters restrict airflow through the HVAC system, causing evaporator coils to freeze. When the ice eventually melts, the excess water can overwhelm the drainage system.
- Clogged Condensate Pea-Traps: A clogged condensate Pea-trap can prevent the HVAC unit from draining properly. Dirt, algae, and debris can create blockages that cause water to back up and eventually overflow into the building.
- Drain Pan Problems: Drain pan problems can also lead to water leaks around rooftop HVAC units. Rust, cracks, improper slope, or an unlevel unit can prevent HVAC drain pans from draining correctly, causing water to overflow and enter the building.
- Condensation, Ice Buildup and Water Intrusion Around Rooftop Units: In winter, rooftop HVAC units that continue operating in high-humidity environments or spaces requiring year-round cooling can produce excess condensation. This moisture may freeze around the equipment, creating ice buildup that blocks drainage, rises above flashing, and allows water to enter the roofing system. Facilities such as printing plants, gyms, and indoor pools are especially vulnerable due to elevated humidity levels.
Roofing Problems Around HVAC Units
While HVAC systems are often the source of rooftop leaks, the flat roofing system itself can also be responsible. Damage, heavy foot traffic, aging materials, and failed flashing around rooftop units can all allow water to enter the building.
- HVAC Maintenance Can Unintentionally Damage Commercial Roofing Systems: Loose service panels, missing screws, dropped tools, sharp equipment, and heavy maintenance materials can create openings or punctures in the commercial roof membrane, allowing water to enter around the rooftop unit.
- Heavy Foot Traffic Can Wear Down Flat Roofing Systems Around HVAC Units: Frequent access by HVAC technicians can cause membrane compression, surface wear, and accidental punctures, increasing the risk of water intrusion over time. It may be beneficial to add roof protection at the tops and bottoms of ladders and roof hatches, and around HVAC units.
- Roof Membrane Stress Around HVAC Curbs and Vertical Flashings: Areas where the roof membrane turns upward around HVAC curbs and equipment are more vulnerable to stress. Gravity, temperature changes, and expansion and contraction can weaken corners and cause flashing to separate.
- Damaged Flashings: Flashing components such as counter-flashing, pitch pans, termination bars, and sealants are designed to protect openings around HVAC units. When they are damaged or deteriorating, entry points for water can form.
- Aging Sealants: Sealants around rooftop equipment can break down due to UV exposure, freeze-thaw cycles, and natural shrinkage. Cracked or deteriorated sealants may allow moisture to penetrate around flashing and equipment bases.
- Rooftop Ductwork Issues: Exterior ductwork can also contribute to leaks when insulation is damaged by pests, weather, or physical wear. Holes in duct insulation can lead to condensation buildup and potential water intrusion that often triggers a roof leak.
How to Tell If Your Roof Leak Around an HVAC Unit Is a Roofing Problem or an HVAC Problem
It’s not always easy for building owners to know whether a leak is originating from the roof or somewhere else. Here’s a quick checklist to refer to:
Possible HVAC Issue
- Leak only occurs while AC is running
- Stops when unit shuts off
- Water is clean
- Appears near supply ducts or directly below the cutout in the deck substrate for the unit
Possible Roof Issue
- Leak both during and after rain
- Leak after snow/ice melt
- Visible membrane damage
- Wet insulation
Of course, the only way to know for sure is to consult with a local roofer experienced in diagnosing flat roof leaks. That’s why regular inspections are so important. Roofers can catch small issues before they lead to larger problems like mould, wet insulation, deck corrosion, and interior damage.
Remember: the longer moisture travels through a roofing system, the more difficult it becomes to identify the original source and the more extensive repairs may become.
FAQs: Roof Leaks Around HVAC Units
Can an HVAC unit cause a roof leak?
- Yes. Condensation problems, clogged drains, frozen coils, damaged drain pans, and overflowing condensate lines can all create leaks that appear to come from the roof.
Why does my roof only leak when the air conditioner is running?
- This often indicates an HVAC drainage or condensation issue rather than a roofing failure.
Can HVAC technicians damage a flat roof?
- Yes. Heavy foot traffic, dropped tools, loose fasteners, and damaged flashing can all shorten the life of a commercial roofing system.
Who should I call for a roof leak around an HVAC unit?
- If the source isn’t obvious, start with an experienced commercial roofing contractor who can determine whether the problem originates with the roof or the HVAC equipment.
The Elite Advantage
When it comes to diagnosing a roof leak around an HVAC unit, you need a local roofing team with experience in this type of situation. Elite Roofing understands that rooftop leaks can involve multiple systems working together, which is why we are uniquely positioned to identify the true source before recommending repairs for your commercial roofing system in the Greater Toronto Area. That’s the Elite Advantage!
Contact Elite Roofing
Don’t assume every roof leak around an HVAC unit requires roof replacement. If you’ve discovered a roof leak around an HVAC unit or suspect your commercial flat roof may be leaking, schedule a professional inspection with us. We’ll determine whether the source is the roofing system, the HVAC equipment, or both, so repairs are targeted to the actual problem.
