Best solution for damp internal walls?

[Djks]

Have an old property we're trying to improve.

We have damp issues on all the walls internally.

Building has been knocked around in the past, and someone has taken up all the floorboards, infilled with bricks and rubble and concreted all the floors. Im reliably told this was 45 years ago.

If you look in any of the air bricks around the property, you can see the broken bricks unclear if any form of dpc was used, I'd guess not, so the damp course in the walls is breached.

So there is no air flow under the building to dry anything out, and the walls are slowly getting worse (wall paper peeling / plaster crumbling behind)

A plasterer came and said there was no point going back to brick and plaster on a bitumen coating.as the damp will come out elsewhere. His suggestion was making a feature wall and just having brick, before I said it was every wall He said he'd get me in touch with a damp person.

Before they come in, Any out the box suggestions? One is composite cladding - but will get dated in time, or just had an idea of the cement tile backer boards if it's possible to plaster? Or just seen Sts construction boards. Both could be fitted to battons allowing the wall to breath behind

 

[jeds]

Trace the actual source of the dampness before you commit to spending lots of dosh on damp proofing. At the very least the walls should be tested for structural dampness by somebody that knows what they are doing and with no vested interest in selling damp proofing materials or services. You'll have to pay but at least you'll know the advice can be trusted. Personally I would test physical samples rather than rely on a meter.

PS. From your description I would be (very) surprised if dampness was rising through broken brick etc.
PPS. If the problem is condensation, ventilated battens will make it worse. Much worse.