Chris Plastow
This condition is called hygroscopic damp, it means that the damp is being absorbed from the atmosphere ( humidity) into a chemical left over from when coal was burned in the fire , this chemical is called ammonium sulphate . It will appear as damp patches randomly , but particularly when it is raining or the house is closed up quite a lot . The render needs to be stripped back to the brickwork and replaced with a waterproof render , which stops the humidity from getting to the amino un sulphate . This is a very common condition but few understand it or know how to fix it , follow my instructions and it will be cured .
