Rising Damp - Any Recommendations To Fix It?

I've found that I have rising damp in one of my internal walls. A guy was here with a moisture meter for another job and he noticed it. There's no pipe in that wall so it's not an internal leak, and the dampness is worst near the floor but gradually decreases until around 3 ft above the floor the wall is dry. The guy said that it's probably due to the shoddy way they often lay the foundations in sections rather than as a single pour. This leaves gaps between the sections which can allow moisture from the ground below to wick upwards.

I've never had this problem before so I checked out the internet how to fix it, and it doesn't seem that big a deal. Basically just knock out the affected damp brickwork and lay a waterproof layer below it to stop the dampness from rising, then replace the affected bricks. I'm not sure what they use as a waterproof layer, but some websites mention a foam that can be sprayed on.

Anyway, does anyone know of a competent local builder who could fix this without causing the roof to fall? I think it may be better to use a professional rather than Somchai the handyman, as fixing rising damp in his wooden shack may not quite be the same.