Could this be damp?

My wife and I bought a main door (ground floor) Victorian sandstone (circa 1890) flat/conversion in Edinburgh almost two years ago now. While a full survey at the time of buying mentioned an elevated (but not necessarily high) moisture reading in the back bedroom we until now have noticed no problems of 'damp'.

This weekend we noticed two separate damp patches on the wall above the skirting (one about the size of a kitchen sink; the other smaller) reaching to a maximum height of approx 30cm . The areas are separate by what appears to be completely 'clean' wall area - approx 1m apart. Would damp not affect all the length of that wall - at least with no breaks like in this example? Is this more likely to be penetrating wall damp?
Slightly more bizarrely is that the wall is not external to the outside environment. Our neighbours effectively share this wall as it forms a part of their hall for their conversion and stairs above (also made out of sandstone). However, approx 4 years ago they had their side treated (apparently successfully with an injection and re-plaster) for the same visual issues highlighted earlier. Could their treatment have effectively 'pushed' or forced the moisture internally to us?

Your help with this matter would be greatly appreciated.

Thanks

Dan

Damp can be localised or widespread, and it all depends on the cause and the routes/materials available for it to soak into the wall.

Basically you need to determine possible causes - coming up, coming down coming through, and times when this occurs - after rain, after cold, after flushing a toilet! etc

Thanks for your reply woody. The 'damp' patches are def. not created from above as the rest of the wall above the suspect areas appears dry. My neighbour has checked above and there is no leaks etc. As it is not an external wall but an internal load bearing solid wall (Victorian house after all) that my neighbour shares (see the previous post.) it is unlikely to have a water seepage problem but I guess it could be to proximity of pipes - a basic investigation showed that their main water pipe runs approx 6ft away (vertically and away) from the nearest damp patch. Having said this, at the bottom of their mains water pipe (where there is access to turn it off) there is no moisture present. Could there still be a odd trickling affect?

I'm thinking of getting in a independent surveyor so to determine a diagnosis (poss - http://www.abbeyis.com). I have been warned against getting in builders specialising in this area due to high chances of inaccurate and differing readings/investigations. I also understand that true 'rising damp' is immensely rare. I have a suspicion (due to the remedial action taken by neighbour) that although their side of the wall may have had a damp problem they have in-avertedly forced it though into my side.

I'll try and get some pictures attached v.soon - this may help us…..or not

Post your pictures.

Dampness has specific patterns for specific casues, and its just a case of elimination of the least likely causes, to come up with the most likely