Rising damp - bridged cavity?

My friendly neighbour has just bought-to-let a ground floor flat in a 60's-70's(?) block.
Problem appeared to be condensation at first, but from the old paint it isn't new, in the corner of the building.
And it's low - from ground, up about a metre.

Outside, the DPC appears a couple of courses over the ground, but there is a visible change in the brick colouring, a triangle about a metre high and 2m long. It's slightly lighter with a dark band at the edge.
There is a gully on that wall, but it looks OK.

Outside is all stretchers (zigzag surface bricks), so I assume there's a cavity.
I'm wondering if the cavity has blocked with debris bridging the dpm.

I assume it's the freeholder's problem IF it's rising, to some extent - dunno.

I could drill a hole, I have a 19mm endoscope.
Are diy variety damp meters any good? Can you tell between condensation and rising damp on the inside?
Do they work on the outside - depends whether it's been raining?? I don't have one but they seem cheap and simple resistance meters.

He can ask the surveyor, but mortgage 180k of 240k so he wouldn't have been too bothered.

zig-zagz bricks (LBC wirecutz?)=probably Cauncil built =probably shyte in the cavity=probably rising damp don`t probably exist

zig-zags? sounds like london rustics to me.

London rustics sounds right. Not council. 10mins walk from Surbiton station.

OK so if it's S in the C, and it's the neighbour's problem, what's the fix?
Silicone injections and wateproof render inside?

Block's 3 floors so they wouldn't like the wall taking down...

ChrisR said:

OK so if it's S in the C, and it's the neighbour's problem, what's the fix?

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When I was a bricklayer years ago and we used to use 2"x1" batten on rope and rest it on the cavity wall ties and pull it up on each level to collect the mortar but many bricklayers never bothered in them days, doesn't happen today because of the insulation slabs.

If you're confident it is mortar debris and to get at it you need to open up few holes but keep these holes far apart then do the middle after the brick is replaced on each end. The most I could scrape out though the cavity was up to 24" on each side of the hole, the bonus would be if there's a corner wall which will allow using a long scraping tool.

Another one I have seen is to put in weep holes along the base of the dpc, doesn't always work though.

Or it maybe just the cavity wall ties which have corroded or is covered in debris!

Generally speaking a cavity wall is approximately 280mm thickness and a solid wall is approximately 230mm thickness, you can measure this on the door opening.

Silicone injections and wateproof render inside?

Click to expand...

I don't think it will work because of the mortar in the cavity, another theory there could be plumbing leak(?) Rising main chopped into the wall(?) Plumbing in the cavity which I have seen!

A good start would be to use your endoscope to investigate in the wettest area

No plummin anywhere near.

I take your point about the silicone and the debris. If the debris goes 2 ft deep then silicone would be too low..

I've been told dpc's can also fail, even this young.

It seems that although my neighbour is the leaseholder, he IS responsible for this because it's classed as INTERNAL!!

Good point about the corner - thinking of a long bit of dexion with the end bent down, half a brick chopped out...

well said, guys -proper brickies LBC rustics...were on our rural Cauncil house....that was a guess

Is there a television behind this damp wall, it's known from the heat of the TV which can do this if it's in the corner of the room, known as "air pocket or trap condensation" The most common trap condensation problem are normally behind the bed headboard

A few more idea as to where the water may be coming from, leaky guttering and the gulley, I have never taken out a gulley that has NOT been leaking and as Masona has pointed out the Brickies back in the day where rough as a badgers arse and snots were a plenty, so cavity may well be bridged.