Damp course

This all depends if the floor is timber and the joists are on a sleeper wall or if solid flooring if the floor is solid concrete every chance a approved dpm hasn't been fitted if timber the joist should be wrapped in a dpc

If the house is that old its possible that it probably has a celler and the dpc system will be old and inadequate for the house now ,,now days we tank cellers out to stop damp over 100 years

Need a new DPC

could possibly be a leak causing the damp . but could also be faulty damp proofing in brickwork or faulty dpm under flooring .

Lack of dpc and water/damp rising from under the floor , just resolved same issue on a job I’m on.

Check under the floor as it may be wet. Or you may have a leaking pipes.

Yes got a tray from floor level inner leaf to 150 ml drap outer leaf also could be insulation problem depending on were the dampness is going two things a would correct

Possibly is that 1930s houses were built with a slate course were as modern day houses are built with a damp course ( DPC). That could be the reason for rising damp internal.

the wall is damp because the wall is cold and the room is poorly ventilated

Several issues could be the case here, most common on this age of build was the step footing design. It was never build of a solid foundation like concrete (although certain people would say the old way was best) movement in the step footings can cause gap in the foundation therefore water can rise up and into it, that said a internal wall is strange maybe a leak on pipe work it may seem odd saying that but you would be surprised how many insurance jobs we do that are leaks internally and is the issue of the home owners to rectify. Hope the above helps. Thanks LMH Estates

These old properties never had a damp course and was most likely laid with no foundation. You can buy a damp proof product that you drill into the wall at low level to help stop this

It is possible for rising damp to occur on inner walls, it may indicate a problem with the damp-proof course because that should prevent moisture from rising up through the walls.

Another possible causes of damp on an inner wall could be condensation.