External pebble dash wall stripes

[Lise Parker]

I am a bit concerned about the horizontal lines appearing on the external pebble dash wall. They look as if they are wet. See photo.
The inside wall is slightly damp too.
Is this due to the roof leaking (there's an old chimney exactly above the stripes) ?
Any insight much appreciated.
Thanks

 

[bobasd]

stand back and in proper daylight pic & post the whole elevation and chimney stack