Richard Newbery
Do i take it that reading your problem is that the doorway was new and cut into the wall disturbing the damp course? If thats the case then a physical DPC should have been placed below the doorframe and up the sides at least 300mm higher than the level of the injected dampcourse obviously if the frame and door is beyond repair then it will need to be removed and replaced ,the frame will need removing anyway to install the DPC ,hope this helps, contact the builder and explain your situation i am sure you will reach a solution
