This is a property with a westerly facing wall. It is tall and exposed. The owner has been there for a long time so knows how the wall has performed over many years. There were one or two issues in the past and the rear living room wall was re-plastered due to a penetrating damp issue. Unfortunately, the original Lime plaster was replaced with plasterboards on dabs.
The problem did not go away and it became far more serious when the wall was subsequently filled with insulation beads. A number of problems materialised over the coming months due to poor quality previous work and cavity wall insulation. Symptoms were, dampness showing up on the walls. Water dripping through the window heads. Dampness on the chimney breasts and water entering the flues and dripping onto the fire grate.
The dampness was showing up mainly after prolonged rainfall and the westerly winds. The cavity wall insulation would prevent the outer skin of wall from drying quickly. The next bout of rain would then soak an already damp wall. The wall would become saturated and rain, driven by the wind, would spill out into the cavity and chimney flues. The beads, wall ties, and chunks of mortar would provide a pathway across to the inner walls.
hygroscopic salts, lack of ventilation to disused flues, leaks around the flaunching on the chimney tops, lack of cavity trays, penetrating damp from wind driven rain, minor cracking in mortar joints, and the cavity wall insulation were all attributed to causing the problems.
Conclusion and Solution
Water will have always found its way into cavity over the years but it would have been less quantities and would have evaporated before it became a problem. When the property was built, the fires would have been in use keeping the flues and surrounding masonry dry. The plaster was also lime plaster and far better at absorbing the odd bit of dampness. The window reveals will have been timber which again would have coped with a bit of moisture. Changes over the years have contributed to a minor problem being a major one. The catalyst, it would be fair to say, was the cavity wall insulation.
The solution was to remove the insulation, re-point where required, ventilate disused flues, repair the chimney flaunching, remove the plasterboards on dabs from the walls and window reveals and re-plaster with Dryzone renovating plaster, Fit cavity trays over the windows and line the window reveals with timber.