Common chimney leaks are caused by poor flashing installation
Chimney flashing prevents water from entering the house from the point where the roof and chimney meet. When the flashing fails, leaks occur at the chimney. In some chases if the flashing is leaking, it could be patched but as any patch job, it is temporary. Since almost all chimneys are different, flashing is a custom project. Just because a home is a new construction doesn’t mean your flashing will last for a long time, actually new homes typically shift and settle therefore the flashing needs to be resealed or replaced. Other times flashing needs replacing is when it is missing, rusted, over patched and when the roof is being replaced.