Very old terracotta roof tiles can be very brittle (called biscuit tiles) and is very difficult to do any repair work on.
Younger terracotta roof tiles can also suffer defects that are difficult to spot.
These tiles can be very resistant to breakage under pedestrian traffic.
But usually hidden under the laps, the edges of the roof tiles are crumbling into powder.
This is called ‘FRETTING’.
The causes of fretting are tenuous. It could be salt in the air, bad batch of clay during manufacture or environmental factors.
This is one disadvantage of a terracotta tile roof.
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