John,

Africans tend to use whatever is easiest to get for their roofs. If they have good reeds growing nearby they'll use them, but if not they will look round for the best...... and closest grass.

The thing to remember is to get the angle of the roof right. Too flat will cause mildew to occur and rot the roof material and too steep will cause the material to become loose too quickly and fall out...... we also try to make sure that nothing overhangs the roof otherwise monkeys get up there and pull it bits...... then you have to reach for the .22!!!