In the summer I had a very well known co. instal DPC to all my external walls on the ground floor, all the plaster taken of these same walls back to the brick and then completely re-plastered. That was Jul. I have only just finished decorating, fixing new skirting boards and laying a laminate floor. My problem is that what looks like black mould has appeared on one of the new walls. Should I go back to them to make them re-inspect and then repair or should I be dealing with it in some other way?
There is no point going back to the dpc installer. A dpc will only offer protection against rising damp. The presence of aspergillus mould (black spot mould) is not found with rising dampness as physical water droplets are required for its formation, something that cannot happen with rising damp.