When leaks occur around a chimney, it's often assumed that the roof flashing is at fault. But quite often the problem is higher up. If a chimney is very old or poorly built, with visible voids in the mortar joints, water can enter through the masonry. It's more likely, though, that the cap is the culprit.

Such was the case with a leaking 19-year-old chimney that I was recently asked to repair. When I got up on the roof to take a close look, I found the usual problems: The featheredged mortar around the perimeter of the cap had weathered away, and cracks had formed in the rest of the cap. These cracks probably started the day the mason slathered...

or Register to read the full article.