Dark patch on external wall

[Dazza Jones]

Howdo?

I have noticed a dark patch on my external brick wall which i cant suss out. Its sort of in the middle of the wall. It is directly behind my ensuite shower enclosure but surely if that was leaking there would be signs inside the house. I have checked under the tray and its all good. We have no signs of new leaks from the shower, but there is evidence of an old leak.
The patch doesnt seem to be getting any bigger.
Its a 3 storey house, 11 year old, we have been in it 6 months or so.
Have added a couple of pictures.

Anyone have any words of wisdom?

Edit to add the chimney isn't a real one.

 

[^woody^]

Possibly from the flue gas. One or more of the flue block's joints leaking.

Or, the past or existing leak from the enclosure has soaked insulation and affected it in that area.

 

[Dazza Jones]

Ahh sorry, one thing I didn't think to mention is that it's not a real chimney, just a pretend one. (If that's what you meant by flue gas).

I've rechecked the enclosure tonight and it defo isn't leaking now.
Woody, are you saying that it may have soaked all the way through from the previous leak and sort of stained the brickwork?

 

[^woody^]

If a cavity is "full fill" with quilt cavity insulation, and this gets saturated, then it loses its water repellancy, so when dampened by future rain, retains the water for a while. This can then keep the bricks damp in a patch.

A lot depends on the wall construction, but the shower is a very strong suspect if that patch is at the same level as the tray.

 

[Dazza Jones]

I'm not sure what's in the cavity, or how to find out if I'm honest, but what's the fix, do I need to do anything or is it a case of letting it dry out, keep an eye on it and making sure it doesn't get bigger?

Thanks for taking the time to reply Woody.

 

[Dazza Jones]

Thought i would update this.

I have discovered that the cavity has insulation. During my investigations i went in the loft and could see insulation wrapped in green plastic poking out of the top near where the roof is.

I also found that the shower was leaking again, this time through a cracked grout line on the side wall. This has now been sorted. I have also made 3 access points around the shower tray for viewing, 2 at same level, 1 below, and can rest assured no more leaks.

The patch remains though. Doesnt get bigger, doesnt get smaller. I have made chalk marks for reference.

I have been thinking about calling someone in to investigate, but unsure who would be best; plumber? Builder? (candle stick maker?) Damp specialist?