Since the rafters are fixed to timber wall plates sitting on the head of the masonry wall then roof spread pushed out those wall plates in the process pushing out the masonry below.
Roof spread remedy.
A case in point would be slates being substituted with concrete tiles a very common occurrence nowadays.
Roof spread affects a roof that begins to move after it is installed.
Roof spread occurs when there is a failure to adequately support the main rafters of the roof so as to prevent them spreading further open in a scissor type action.
Some of these can support the roof and prevent ridge sagging and wall spreading.
Roof spread occurs when the downward pressure of the weight of the roof starts pushing against the rafters enough that the structure itself begins to move.
So fixing the problem as soon as possible is vital.
Roof spread can be dangerous for a house and very damaging for a roof.
Factors that cause the situation include bad construction improper materials and water and rot problems.
Roof spread is often caused by the roof timbers being subjected to extra weight weight that they were not designed for.
Either the roof starts moving downwards or the walls start pushing outwards.
This article describes and illustrates the different types of support that prevents roof sagging and wall bulging at buildings including definitions of collar ties rafter ties and structural ridge beams.