Basement Tanking has failed - contractor not interested??? what to do???

[firstchoice]

Around 9 years ago the previous owners of our house had the basement (approx. 450 sq ft) tanked out.
All walls and floors were coated with waterproof membrane and then coated with concrete and Biokill Crown chemicals were used.

We have had damp, yellow staining, paint bubbling and water coming in at the joins of where the concrete meets between the corridor and rooms.

We called in the contractor (work guaranteed for 10 years) and he said: 'that's not damp'. I said, yes, it is and local surveyor recommended we get you back in. He then huffed about it 'never happening before' and the like.

Has agreed to strip plaster on - some of the affected areas and recoat floors.

Now, he's spoken to H (wimpy with trades) and said the floors don't need recoating and that the prob is 'no extractor fan' (windows and door ventilation) and that 20% damp in a treated basement is fine and that the floors don't need re-coating?

Is he right???

I don't know what moisture levels are acceptable, but we've recently had issues with damp in our treated basement as well, although in ours it wasn't tanked and should have been (only some of the walls were treated with a membrane).

Our builder got in an independent damp expert who provided us with a full report detailing where he thought the damp proofing had failed and his recommendations for what we should do. This has been really useful in negotiating with the company who did our damp proofing work as to what guaranteed work needs to be redone, and in pricing additional work.

Could you arrange something similar? If nothing else it could give you piece of mind that what your contractor says is correct.

A 10 year guarantee doesn't sound that long, ours has a 20 year guarantee, although I've no idea what the norm is,

If water is coming in, have you checked all the land drains to see if water is flowing down them properly and they are not blocked?

Yes, drains checked milly

Lones yes, 10 years not v long is it?

The work cost the previous owners £14K so I think it should last!