I have an occasional leak, it doesn’t leak in every rain

Leaks that only occur during wind-driven rain are much more likely to be from vertical masonry surfaces, like brick, stucco, or stone walls and chimneys. A roof leak will usually occur in every rain simply due to gravity. “Occasional” leaks in a historic home can be difficult to diagnose, so your roofer will be glad to hear any details that you can provide about what the weather conditions were like when the leak did occur.