A commercial roof that leaks only in heavy or wind-driven rain still needs investigation. Drainage conditions and exposed roof, wall or equipment details may behave differently between storms. Staying dry during a light shower does not establish that the building is watertight. Record the timing and affected locations so an investigator can test a specific explanation rather than repeat an unsupported patch.
This guide addresses intermittent storm leaks in commercial and industrial buildings. It does not predict which component has failed at your property. If water is entering now, use the active commercial leak response guide and keep people away from electrical exposure, sagging ceilings and other unsafe conditions.
Separate rainfall intensity, duration and wind
“It only leaks in bad weather” combines several different observations. A short downpour, hours of rain and rain arriving against one elevation may produce different clues. Describe what you observed, and label anything you do not know.
| Pattern | Record for the investigator |
|---|---|
| Leak during a downpour | Start time, affected area and any overflow observed safely from ground level. |
| Leak after several hours of rain | Approximate delay, whether it has happened before and the locations involved. |
| Leak with wind from one direction | Affected side of the building and the basis for the wind observation. |
| Dripping continues after rain stops | When rainfall and visible dripping stopped; changes in spread or intensity. |
| Similar water in dry weather | Equipment activity and any related plumbing or HVAC service history. |
These observations narrow the questions; they do not prove the cause. An official weather report may add context, but conditions reported at a nearby station are not a measurement at your roof. Avoid assigning a rainfall threshold that has not been established for the property.
Review drainage and exposed building details together
Drainage conditions
Roof outlets and the path leading to them deserve review when a complaint changes with rainfall conditions. Ask whether the relevant issue is debris, the roof-to-drain connection, downstream piping or another aspect of the drainage system. Cleaning and repair are different scopes.
Johns Manville's maintenance checklist includes drainage, flashings, penetrations and rooftop equipment, as well as inspection after unusual weather. For more detail, use Brady's roof drains and scuppers guide and ponding-water decision guide.
Roof, wall and equipment transitions
Consider adjoining details when the affected area is near a parapet, wall, window or rooftop unit. A complaint associated with one wind direction is useful evidence about exposure, but it does not prove that the roof membrane is the entry point.
The EPA's moisture-control guidance treats roofs, walls, windows, plumbing and HVAC as connected moisture-management concerns. Water can move through or along an assembly before it becomes visible. The investigation should therefore distinguish the source, the route and the indoor symptom.
Where the complaint is near equipment, review roof leaks around HVAC units. Where the source is unclear, the whole-building water-intrusion guide helps organize the possibilities.
Keep one incident log for the property
Use a consistent record for every reported location. A shared log is especially helpful when tenant staff, security and the property team observe different parts of the same event.
- Identify the location: property, building, suite or bay, and a fixed interior reference.
- Record the timing: first observation, apparent changes and when visible water stopped.
- Describe the weather: rain and wind observations, with uncertainty stated.
- Document safely: photographs from permitted areas without touching wet electrical equipment or entering damaged spaces.
- Record the impact: restricted areas, affected operations and immediate actions taken.
- Attach history: earlier incidents, relevant roof or equipment work and previous repair records.
Keep descriptions factual. “Dripping at column B4 after rain began” is stronger evidence than “all roof seams failed.” Do not send staff onto a roof to improve the record. OSHA's roof-tarping guidance specifically cautions against tarp installation during rainy or windy storms.
Use the interval between storms to plan the next step
A dry day is an opportunity to review records, arrange safe access and define the investigation. Ask the contractor what can be established on that visit and what would require suitable testing or further observation. Our commercial roof leak detection guide explains how to assess those proposals.
Before authorizing work, distinguish a confirmed defect from a possible contributor. Ask for the repair location, scope, compatible method and outstanding questions. If temporary protection is proposed, identify the permanent follow-up separately. A coating should not be selected simply because the leak is intermittent.
For Southern California properties, Brady can discuss roof leak repair coordination, drainage maintenance and building water-intrusion repairs. For a property in Temecula or another service-area community, include the address and site constraints so the appropriate scope can be discussed.
Common questions
Should we wait until it leaks again before calling?
No. Existing observations and records can support a review between storms. Explain that the leak is intermittent so the provider can identify what can be investigated safely and what may need further evidence.
Why can water appear after the rain stops?
The visible symptom may be delayed as water moves through the assembly. Record the timing and duration; neither proves the source without investigation.
Should our staff hose-test the roof?
Do not improvise testing. Controlled testing needs a suitable method, authorization and protection for affected spaces. Have qualified personnel determine whether it is appropriate.
Will a roof coating stop an intermittent leak?
Not automatically. Drainage, failed details, wet materials and system condition require evaluation. The repair should address the identified cause before a coating is considered.
Request an intermittent roof-leak assessment
Send Brady your property location and incident history, or call 909-293-9861. Include safe photographs and earlier repair information so the next conversation starts with the conditions at your building.