Help diagnosing and fixing damp patches on wall

[cazzabazza]

We have two fairly large damp patches on an exterior wall, under a window and above a radiator. There is also a patch of damp and (what I assume are) rust patches coming through near an old plug socket on the same wall.

We had initially thought the leaks were from a leaky window frame, so we sealed around the frame and had hoped the damp patches would dry out over time. It's now been several months since the window frame was sealed, the property has been empty, and we've no rain in a long time but the patches are still quite damp.

Could this be a leaky pipe inside the wall? Coming from the radiator, or somewhere else? Rising damp? It's not condensation as the property has been empty for many months.

I don't really know what type of tradesperson or company we need to contact to diagnose and then fix the problem. Do we need a leak detection specialist? A plumber? A builder? We really need this fixed ASAP as it's vacant and we are trying to sell, and we don't want to get ripped off.

Any advice would be very welcome!

Anyone?

that's quite a lot of water and it certainly looks like it's coming in round the windowftame and leaking through in the bottom tight corner.

It might be getting in above the window and finding its way round ot inside the frame. Is it plastic or wood?

Go outside and look for signs of a leaky gutter or an overflow pipe. Look in the room or loft above, whether it is a loft or a bathroom or a bedroom. There may be a plumbing leak getting into the wall.

It could be coming in under the window sill. Our windows do that. Or from any 'joins' externally. So from a nail/screw of a pipe running externally.

What about the gutters, downpipes and pointing outside? Any sign of issues there? If it's got really damp then it can take a long time to dry out. Is the ground level outside above the damp proof course or over any air bricks. A leaking pipe in the wall or a leak from above coming down through the cavity could be the issue.

Thanks to everyone who's commented so far, some really helpful things to look at.

It's a wooden window, however we sealed around the outside of the window frame earlier in the year, and the damp is worse now than it was before, despite the warm dry weather we've been having.

We are wondering whether it's a leak coming from the flat above us so I think we need to get someone in to investigate. What type of tradesperson would be the right one to come and investigate?

A general builder? Leaks are notoriously difficult to identify and fix though. It's a process of elimination, you identify the most likely cause, fix that, wait to see if the problem has gone away, if not, go onto the next problem. Some helpful hints here.