Damp kitchen walls

My kitchen is a single storey built onto the main house. The flat roof had been leaking and has been recently replaced. The exterior wall of the kitchen and its wood doors and windows are damp from the ground to about a metre high, this may be unrelated to the leaking roof. The existing damp course may have been ineffective, I'm not sure when was done. I'm not sure what course of action to take. Do I need a damp specialist to advise? Would it be cheaper to replace the entire wall with bi-fold doors? What would repairing the wall involve in readiness for replacement windows and doors?