Not all leak at chimneys are as easy to spot as the one in the picture on the left.
Chimneys leaks show up as brown staining in the ceiling area that progressively gets worse. This is usually caused by a deterioration in the flashings around the chimney.
Either the overflashings that are set into the chimney have developed cracks (or fallen out), or the apron and soaker tray flashings are starting to crack.
Over time, lead flashings will crack. This is due to stresses caused by heat from the sun – especially where the flashing has been stretched over an object initially.
The repair options are either to replace all the apron and soaker flashings with new lead or with the new ‘lead free’ flashings like “Wakaflex” – or to simply clean up the cracks and repair with roofing silicone.
Whilst the new flashing option is the proper ‘belt and braces’ solution, I sometimes find that a semi – permanent fix with the silicone will provide many years of service.
Which is the more appropriate option depends on the age of the roof and the owner’s situation.
The video below shows how to locate a leak at a chimney on an old terracotta tile roof: