Damp rising into floorboards through concrete

Usually you would leave a slight gap between timber and the brick. Joists would be wrapped in plastic. A dpc would work but usually fit above floor hight.

If the timber joists are sitting on top of the concrete I would apply a liquid membrane TANKING to the concrete floor this will prevent any dampness drawing up through the concrete fix rubber to the underside of the timber battons (durabella runners) this will take any discrepancies out the floor. If the floor has a concrete solum the timbers should be resting on wallplate with DPC underneath it to stop any dampness coming up and hitting the timber joists or flooring there should be sufficient clearance between the timbers and masonry. The timber ends should be wrapped in plastic DPC some people say the timbers can't breathe and sweat when wrapped in plastic but the timber ends are certainly protected and can't draw moisture from the masonry when wrapped in plastic. All dampness should be hacked of the walls 1m to 1.2 high membrane fitted and renovating render applied to stop any future dampness exposing itself within the property.

Leave a gap between the floor an brick wall Take off the damp on the wall then treat with a membrane and renovating damp proofing plaster

This condition is interstitial condensation, it’s caused by poor air exchange under the floor timbers, yes you can isolate the timbers from the wall but ultimately the floor will have wet rot or worse, dry rot , and it’s all because of poor ventilation!

It will need sume ventilation bricks because he has no ventilation to the floorboards