30-year-old basement is damp. Seal it? If yes, how?

Try to get a few more quotes. Preferably from a local construction company with a small number of employees. My offer for excavating, new bitumen coating, insulation, dimpled membrane, and backfilling again is roughly 18k for about 60m2 The quotes have varied significantly. The shocker was a company that was referred to me online. They wanted 72k:oops: but with additional injection

I recently had a company here that sealed 2 weak spots. They first looked to see where the problem was and also specifically worked on these areas. One spot that I had identified was, according to the expert, condensation, because I had probably ventilated too much in the summer (beginner's mistake). The whole thing cost €2,000 net for a 2-meter-high crack in one corner and a wall measuring 1.5 x 2.25 meters. So far, everything has remained watertight even during continuous/heavy rain.