Such walls are amongst the most common forms of masonry to suffer collapse, and they are unfortunately one of the commonest causes of death by falling masonry.
Waliau o'r fath yw'r gwaith maen sydd fwyaf tebygol o ddymchwel a gwaetha'r modd, cerrig sy'n cwympo oddi ar waliau yw un o'r achosion mwyaf cyffredin o farwolaeth gan waith maen.