This is when the inner leaf of the wall after insulation becomes much warmer and this has a knock-on effect of pushing condensation away from the inner wall.
This can cause condensation to form within the cavity because the dew-point, with warmer air, gets pushed back and out towards the cold outer wall, condensing and forming in the brickwork itself. This problem comes into its own during winter time when the water now trapped inside the bricks actually freezes, expanding as it does, and forming cracks to the bricks. Over time this can cause seriously expensive brickwork repairs, or in the case of smooth render or pebbledash, it can push the wall surface away from the bricks, causing what’s known as “hollow render” or “blown pebbledash”.
Exterior walls being in a poor condition
This is usually due to either a lack of maintenance i.e. damaged pointing or cracked render, severe weather conditions, or more typically, the fact that the external walls have lost their weatherproofing ability. When this happens, the water that rains on to your walls outside, gets soaked up inside the bricks. This normally would stop at the cavity and would not pass into the house, although a good way to spot this is if your interior walls feel cold to the touch, even when the heating is on. So the filling inside the walls starts to transmit the moisture to the inner leaf or wall, causing damp,