Rising damp or lateral ingress?

JT1987LBN

stuart45 said:

Look for a black line in the bed joint. You might see it just below the door frames. 

I found it roughly one and a half bricks up from the concrete path. It only shows in small places, I assume due to the age of the house (1969) that its perished on the surface? but I also found it on the inside! below is a close up of an inspection hole from one of the bedrooms. I've not gone all the way through to the cavity yet so I'm not sure whats going on in there. 
 

Doozergirl

So your DPC is above the floor line.   You have an ingress issue but the plaster internally is breaching it and pulling it up the wall.   

You need to remove all of the plaster below the DPC so that your plaster line is above it.  Your skirting can cover the gap.  

I would also make sure that the new french drain is lower than the recommended two courses. 

I think your cavities do need to be checked as well.  The water shouldn't be carried through.  

stuart45

The DPC is high. It normally is put on at slab level, the DPM comes up and laps it, then the screed is on top.

JT1987LBN

Great information thanks Stuart45 and Doozergirl. We've now got two companies booked in to provide quotes for the french drain later this week. Would a borescope camera be the best/most cost effective way of checking the cavity? 

Doozergirl

In a word, yes.  I've heard of people on here buying their own.