Why equipment is a weak point
Everything gets harder when the membrane has to run up a curb, go around a pipe or stop against metal. Watertightness then depends on flashing, pieces cut by hand and sealants.
Three things work against these details. Equipment vibrates. Metal and membrane do not move at the same rate between summer and winter. And sealants dry out long before the membrane reaches the end of its life.
A preventive roof maintenance inspection therefore spends time around the mechanical equipment.
Places to watch
- Unit curbs. The unit sits on a raised frame, and the membrane runs up its sides. The upstand must be high enough, well fastened and covered by counter-flashing.
- Pipes and electrical conduits. Each one crosses the roof in a sleeve or a pitch pocket filled with sealant. A cracked sealant lets water run down the pipe.
- Supports set on the membrane. Wood or concrete blocks carry pipes and ducts. Without a protective pad, these blocks wear the membrane as they move.
- Anchors. Antennas, signs and guardrails are fastened through the membrane.
When the leak is not the roof
A ceiling stain under an HVAC unit is not always a roof leak. On the mechanical side, frequent causes are:
- A clogged condensate drain that overflows.
- Condensation on a poorly insulated duct inside the building.
- An access panel not closed properly, letting rain into the unit.
Damage from service visits
The technicians who service the mechanical equipment are not roofers. They set sharp panels down on the membrane and drop screws. Two measures reduce this damage:
- have us install protective walkways between the roof access and the units
- ask contractors to pick up screws and debris before they come down
Adding or replacing equipment
Installing a new unit is often the moment a sound roof becomes a leaking one. Have us seal any opening or fastener through the membrane, with materials compatible with the existing system.
Before the work:
- Check the conditions of your roof warranty. Some require going through an authorized roofer.
- Have a structural engineer confirm the load if the equipment is heavier or placed elsewhere.
- Fit our visit into the ventilation contractor's schedule, not after the fact.
Frequently asked questions
Who should fix a leak around an HVAC unit?
The repair falls to us or to the ventilation contractor, depending on the cause of the leak. A faulty flashing or upstand is our work. A condensate drain or a duct belongs to the ventilation contractor. First have someone establish where the water comes from.
Can my tenant install their own equipment on the roof?
A tenant's right to install equipment on the roof depends on the lease. From the roof's point of view, require notice before the work and require every penetration to be sealed properly. Consult a legal advisor on anything related to the lease.
Should old abandoned equipment be removed?
Yes, it is better to remove old abandoned equipment. A unit out of service keeps its flashing and sealants, which keep aging with nobody watching them. Removing the unit and closing the roof eliminates a weak point.