Although my house is not new, I have owned it from new and the problem has existed since I moved in 7 years ago. There has been a damp patch on the external side of my house that has always been triangular (larger at the bottom) but has got broader each year. In summer it dries leaving a white mark in its place.
I have had the builders round, the surveyor who oversaw the build and NHBC (who came for a separate issue) and all say don't worry about it. However, each year more mortar falls out and it gets bigger so I am concerned. The water mark originally became visible below a pipe that transports overflow water from the water softener. When I moved in, this did not work properly and was dumping water, likely salt water, out of the pipe. The builders drilled some holes in the mortar and in the brick to see how far the water penetrates. They said the bricks are dryer deeper in so not to worry. There is no damp patches inside the house - the inside is the garage. Today, a good damp November day, I have gone out to look at it and I can scrape out some of the mortar with my finger. In my view this is only going to get worse. I can see what looks like a part of the DPC that overlaps near the area in question.
My questions are:
(1) Any ideas what it is - rising damp?
(2) Could it be poor mortar and could repointing stop the problem?
(3) Should I get a DPC injection put in - I am a bit unsure about this as there is a DPC in place but may be defective (this is the only part of the house where this particular issue exists)
(4) Should I be more pushy with NHBC - they say there is no structural damage so it does not apply
(5) Should I get a surveyor out who specialises in damp / water issues? Can anyone recommend one in the Cambridge area?
Additional information - The house has piled foundations on clay soil. The floor is suspended concrete piers on beams (I hope I have explained that correctly). A large surface water drainage pipe runs underground by the side of the house. I have had a camera survey on this and it is fine. The ground does get damp in that area but this is normal for the clay soil. Any advise / assistance greatly appreciated!
