The roof void of a building should always be accessed, as this is an area that can tell a lot about the age and condition of a building as well as the watertight condition of the roof coverings and flashings.
Some roof voids however do not have sufficient room for bodily access, but in most cases a roof void manhole is in place to provide access to the interior of the roof. A very bright LCD wide beam torch is used to inspect the interior of roof voids and accessible timbers are tapped and probed.
The tops of the walls around bathrooms and wet areas are important areas to check for signs of termite mudding and damage.
An overview of the electrical wiring is often best done within the roof void to look for obvious signs of handyman electrical or perished cables.
The true condition of old sheet metal roof coverings is best determined from within the roof. Moisture condensing on the under-side of the metal sheeting can cause extensive damage and corrosion over time. Leaks are often more easily located from within the roof.