The theory was putting too many nails in that small timber would be the situation that triggers a split. I.e. many smaller plates (6 on each side was the intent) vs fewer larger ones.
Hey everybody,
~1950's two storey hip roofed house, with part of the roof extending down through the 1st [UK] floor:
The original rafters are suprisingly small (45 x 70mm), despite some of them going nearly 8m to the apex. The main hip section of the house has been insulated for a while, but...