The Biggest Culprit!

Following on from yesterday I have now dug a ditch all along the rear wall of my house.  I discovered this air vent.  But, there's not even any point to it...  You would normally have air vents if you have a timber floor or other suspended floor but I don't.  So all this vent is doing is letting water into the cavity...  which is why my internal wall is now damp.  The DPC is just below the vent.  And who would cover over an air vent anyway?????  The earth was up to the top of the damp bit of wall and there was a layer of stone chips on top so I have never noticed the vent before...

I now have a plan of action.  Let the wall dry out as best it can given the forecast.  Wire brush the wall a few times.  Repoint (some is non-existent!).  Then backfill with a waterproof membrane against the wall and a geotextile membrane to the rest of the ditch and fill with stones.

Doh!