Bungalow built circa 1970 with solid floors throughout. Severe damp inside at floor level and lower walls. DPC visible on outer skin is level with interior floors, and well above ground level outside. What means of dampproofing of the floors was used in 60's and 70's? was a membrane used and if so what type? Also any ideas how to remedy this. I am wary of damp proofing specialists as they will try to sell a chemical DPC instead of solving the problem.
TIA
TIA