Can someone help. Bought house in September with flat roof extension. The walls were thinly painted over plaster I noticed n flaking n cracking. Over last month paint coming off badly in patches. Behind dishwasher was a leak behind plaster board. This was sorted as compression valve. Think that's right. But in extension by pipes it's peeling badly. N gets like fur on it. Just noticed more on other wall. Someone said to remove air brick on outside as this was the cause. Pulling hair out as want to decorate. 