Civil Engineering Reference
In-Depth Information
Moisture vapour rising from the home below passes through the ceiling and insulation into
the cold atmosphere of the roof and will, under certain conditions, condense into water on
the coldest elements within the roof space. These cold elements are invariably the metal
fixings used to construct the roof and of course, in the case of a trussed rafter roof, the nail
plates used for the trussed rafter assembly itself. Clearly this wetting can lead to deteriora-
tion of the metal fixings and, if continued for long periods, to the deterioration of the tim-
bers if they are not fully preservative treated.
