Opinion on this stain on this wall? (asking for a neighbour)

[TonyRPH]

This wall forms one side of the main supporting walls for my neighbours house, which is built over a double garage.

A strange stain had developed in an arc, with some kind of residue. Anyone have any idea what this might be?

I suspect there might be a leak? We don't currently have access to the other side as it is closed off (it's very close to an adjacent building) but there is also a gutter that runs along that side of the house.

Additionally, he has concerns about the lowest row of bricks - but I think these are a different grade intended for foundations, is this correct?

Thanks in advance.

[TonyRPH]

Bump for the week day folk.

Any ideas?

[TonyRPH]

dickymint said:

Drill a hole and take a look with an endoscope?

We could do this, as I have an endoscope.