odd shaped damp patch on outside wall -see picture

[wez1981]

We moved into a 1913 built bungalow this winter, and as the days have got longer I have noticed an odd shaped damp patch on the outside of the bathroom wall.
I have pull out the bath panels and no leaks. The mains water does come in at this point but today ee read the meter before going to work, and it didn't change, so I can assume no leak.
has anyone any ideas.
I have done some sizeable diy building projects but have never delbt with damp before.
could do with some advise
cheers mark

 

[KenGMac]

wez1981, HI.

Is the rainwater gutter above the damp area allowing rainwater to drip down on to the area of dampness you have captured on the uploaded image?

Water escaping from a rainwater gutter will splash up the wall?

Ken.

 

[wez1981]

There is no guttering above this wall as it is the side of the house, the patch is directly below the apex

 

[DIYedboy]

It's highly likely that the pointing is knackered, a 1913 bungalow, that's unusual

 

[KenGMac]

wez1981, hi again.

Is the affected wall a cavity brick wall or a solid one brick thick wall?

If it is a cavity wall, is there any Cavity insulation installed? If so it is possible that the Insulation is preventing the rain water trapped in the external brick from venting into the cavity?

Is it possible? that the stain is some sort of chemical contamination?

You have proved no mains Water leak is there a waste water leak?

Ken.

 

[wez1981]

The walls are solid, and no chemicals near, I think I have eliminated water. Also the pointing looks good, unless looks can be deceptive