If you had damp in your property, how would you describe the smell?

[Plaugey]

As the title says really. There’s an awful smell filling one of our rooms downstairs and it’s been there for a few years. No visible signs of damp, everything has been changed, flooring, skirting, doors, the only thing we haven’t done is replaster in there, but I have repainted the walls about 6 times. I’m at a loss and can only assume that the smell must be damp. But it doesn’t smell how I think damp would.

definitely no dead rodents / birds in chimneys as we’ve already exhausted that and the smell has been here since we moved in.

Water could be leaking from the grouting on the tiles in the bathroom down the wall.
The area under the bath will be completely dry as the water and dampness could be travelling behind the tiles.

I guess I would describe it as a musty smell but it always, always got worse at night, i.e. the smell was stronger then. As for where is the mould if so, one of our rooms smelt of it badly, we got everything ripped out, plaster too, so back to bare bricks. There was some rising damp which had clearly caused it, even though there was no obvious sight of mould. Only after that was fixed and the room replastered etc did the freshness return.

There was a smell, but we thought it was the damp from the bathroom next to the toilet. It was only when we knocked down the connecting wall that we found the leaking pipe in the wall.