Figure 177 and 178 below

To be able to understand the construction of old roofs and especially when trying to determine exactly why a roof has failed it is essential to take a careful and methodical approach. Each course should be numbered and photographed. If the photographs are taken perpendicular to the roof surface and scales are included, on site measurements can be checked later.

(Terry Hughes).

Figure 178

Good photographs with scales allow the construction of a roof to be analysed in detail. If a series of photographs is taken as each course is removed the slating layout can be reconstructed. This often reveals unexpected details as in Fig 179

(Terry Hughes).