We have lived in our house for 2 years and recently found damp affecting most external walls and one interior wall was very wet also on pulling back some lino in the downstairs toilet the concrete floor was damp amd showing signs of mold/mildew. I know my patio has been laid directly ontop of the existing patio and therefore I am concerned tjat it has been laid above the dpc. My landlady had a builder come round and he said no the patio is fine and has drilled holes in all walls and injected a gel or cream type dpc, he says this will attract the moisture from the walls and solve the problem. However other ppl I have spoken to (not builders but family working as labourers and my dad who is quite nifty with diy and a handyman I asked before I realised thw extent of the damp) all believe the patio is too high and needs lowering and another builder who my landlady described the situation too bekieves the same so I am slightly confused and concerned. I have checked my neighbours and their dpc is identifiable by a black line that their airbrick sits on and thwy have a good 3 brick courses between their back door and their ground level where I only have 1.5 courses. Obviously I hope for my landlady that the first builder was right but if he isn't I am concerned that he may have treated the symptoms so to speak but not removed the cause. I have attached pics in the hope someone may be able to identify the dpc for me. The first builder said thw original dpc is where the house steps out but as I say my neighbours house which is identical the dpc os considerably lower. Thankyou in advanve for any help and apologies if this is a stupid question 
