A friend is having problems with a damp wall. A builder tried to fix the problem by replacing half the roof but a year and £7k later the wall is still damp.

I've had a look and the house is on the boundary with the neighbour whose driveway runs alongside it with a small gap between. The ground between the house and the driveway is about 50mm below the driveway. The mortar at the base of the wall is cracked, crumbly and in some places missing. The render generally looks OK.

My theory is that when it rains heavily they are getting a lot of water sitting around the base of that wall and it is soaking in and causing the wall to be damp.

Is this a crazy theory? Any other ideas for what could be going on?

I'm trying to attach some pictures..

pic 2

Where is the DPC? .It needs to be 150 mm min above the drive surface. I am suspicious that the brick paving may have been added on top of existing level by not excavating enough for the drive base. It looks like a cavity wall so if it is penetrating from the outside the cavity must be bridged

I'll try and get a picture of the inside for you.
From memory it felt damp and there were instances of paint blistering.

In regards to it being condensation I guess that would suggest that inner leaf is too cold? I'm pretty sure it has had cavity wall insulation so i would have thought the walls would be too warm for that.

They did have a lot of condensation on the windows though and did mention that they try and air it out most days which sounds a right pain.

Thanks

That is a good point. I will check if the chimneys have been insulated.
If not how do you insulate a chimney?

If the chimney has been insulated then what is the solution here? Better extraction/ventilation?