Internal garage wall leaking?

[oiduts]

The single skin wall on my integral garage is suffering from water seeping through the brickwork. The offending wall is visibly wet on the inside and outside of the house.
I'm guessing this is due to driving rain onto the outside skin, which at the garage becomes an internal wall. Though I've checked the guttering and damp course which are both fine.
I was wondering if this is a common problem with integral garages constructed in this way? Or is there a way of avoiding this issue..

 

[^woody^]

Single skin walls (and the outer skin of a cavity wall) can be saturated in heavy rain within 1/2 hour.

If this is an issue for you, then you could coat the outer face with a silicone water-repellent like "Thompsons"