Damp/condensation Help

Apodemus

A new injected DPC is exactly what I would expect any cowboy builders to suggest!  I'd still go with removing six inches of that concrete along the length of the path, then digging it out to below the dpc so that you can see what is going on.  Then either leave it open so that it can breathe and dry out, or (if you must) refill with coarse gravel to form a french drain.

With regard to what you learned from your neighbour, is their house identical to yours?  At 1954, would you not be nearing the end of high cistern toilets?   Is there any evidence of an old pipe that could be feeding your damp?

FreeBear

PaulC0 said: They confirmed that these houses are poured concrete and that excess may well have spilled into the cavity as it was being built, causing some bridging. 

You need to get a camera in the cavity to confirm this - Might be difficult if you have any insulation in the cavity, so it might be easier to remove a brick or to on the outside wall. Should be fairly easy with lime mortar, although any render over the top will add to the "fun".

Had long term issues with damp here that no amount of chemical injections or waterproof anything slapped on the walls would have cured. Took a few bricks out just above the DPC and removed a wheelbarrow full of sand and brick debris that had been in there from when the house was extended (or possibly from when it was built). Total cost, less than £10 for a bag of NHL3.5 lime & sand plus a days work.