Do this first
What to do right now
- Protect people and stock first: cordon the area, move inventory and electronics, put down containment.
- Kill power to any circuit where water is near lighting, a panel or data equipment.
- Log everything, time the leak was found, photos, affected units, inventory damage. You will need it for insurance and possibly for the lease.
- Check the lease or management agreement for who is responsible for the roof, and notify the other party in writing today.
- Get someone on the roof to look at the HVAC curbs, drains and parapet terminations before the field of the membrane: that is where commercial leaks almost always start.
- Book the permanent repair for the first dry window in Corona, not for the middle of the storm.
Where commercial low-slope roofs leak
Commercial roofs carry far more equipment than residential ones, and equipment is where the water gets in. The usual suspects are HVAC curbs where the counterflashing has lifted or the pitch pan has dried out, condensate lines dumping onto the membrane and eroding it, roof drains where the clamping ring has loosened or the strainer is gone, scuppers packed with debris, parapet coping joints, and the seams around every conduit and gas line that has been added over the years without a proper boot.
Add the traffic. On a building with rooftop units, technicians walk the same route to the same unit for years. Without walkway pads that path becomes a compressed, abraded strip in the membrane, and eventually it splits.
Getting to the source quickly
Commercial buildings usually have a suspended ceiling and sometimes a plenum, so the visible drip is often a long way from the breach. Experienced crews work from the roof side, checking penetrations upslope of the interior stain, and use infrared or capacitance moisture scanning on larger roofs to map the saturated area rather than guess. On a 40,000-square-foot roof this is the difference between a targeted repair and a week of exploratory patching.
Insulation is the expensive part
The membrane is a small fraction of a commercial roof assembly. Below it sits polyiso insulation, and wet polyiso does not recover: it loses R-value permanently, corrodes the fastener plates, and adds weight. A leak that ran for a season can mean replacing far more insulation than membrane. This is the argument for immediate response rather than waiting for the budget cycle.
Practical points before you sign
Verify the licence at cslb.ca.gov, roofing is the C-39 classification and C-39 contractors must carry workers' compensation coverage even without employees. Ask for a certificate of insurance naming the building owner as additional insured before anyone goes up. If tenants are operating below, confirm how hot work, odour and access will be handled during business hours. And if the roof is under a manufacturer's system warranty, the repair generally has to be made by an approved applicator or you lose the coverage, check that before you dispatch the cheapest available crew.
