The primary function of a DPC is to prevent water from rising up from the substructure into the external walls. It is critically important in timber frame construction that DPCs are installed in the correct locations, such as in the following areas:
At the bottom, sides and back of window sills.
Around lintels and lintel angles.
Around all external opes and timber cavity barriers.
Differential movement often occurs in timber frame buildings. To accommodate this movement around sills, a special forward sill is required to be installed. This type of sill is solely supported by the masonry outer leaf and must not be attached to the timber frame. To further accommodate differential movement, a gap should be left between the sill and the window frame.
