There's a stream in my house

[Hugh Jaleak]

Might be worth investigating that before doing much more. If there is reliance on an old storm drain or soakaway which has now ceased to function, that might be a big part of your issue.

 

[kingandy2nd]

I would check your insurance and then get them involved, as it could be costly and they will do all the liaising with neighbours and relevant parties and anything legal that needs dealing with or putting in place.

Given the house has only recently been purchased (and therefore I'd guess insured), it is unlikely the insurers will get involved as this will be determined to be a pre-existing issue).

 

[^woody^]

Given the house has only recently been purchased (and therefore I'd guess insured), it is unlikely the insurers will get involved as this will be determined to be a pre-existing issue).

Is it pre-existing?

Regardless, its a new discovery to the owner so should be covered

 

[kingandy2nd]

Given the floor, etc was soaked through I don't think the owner can claim it's a brand new event. Wonder what the survey said...

 

[mrrusty]

The fact that there is a piped drain suggests to me this has been an issue for a long time. I think whilst looking for the source/cause may be helpful, I think I would try and build a solution to the run off rather than a cure. Would a block and beam suspended floor be better than timber in this situation? It won't be a big area.

 

[mrbiscuit]

Just to let everyone who has contributed advice on this thread know, I've had a structural engineer and a builder who deals with this kind of problem have a look.
The agreed solution is to dig a drain channel network under the room that will lead to the drain storm drain entrance near he front door.. Ultimately, I have to report that the wooden joists will all go and a concrete floor will be laid throughout the ground floor.
I'll post an update as work goes along.
Thanks all.