How do you prevent dampness passing from the external wall (above the roof and outside the new extension) to what becomes an internal wall (inside the new extension).
When the external gable wall gets wet the damp will tend to migrate down through the wall into the interior of the new construction possibly damaging plasterwork and decorations.
When constructing a new house a cavity tray is usually built into the gable to stop that.............however what do you do with an existing (in my case, rendered) gable wall.
Do you just take a chance & hope it doesn't travel that far?
