Damp on floor near base of Chimney

[nks2008]

My house is a 1920's build, single cavity construction. I had wet walls across one side of my dining room, the wall had been injected with a DPC before I bought the house, and the work was guaranteed so the guy came back and removed the plaster etc and injected again, this time a 15cm higher.
So I thought the damp issue had been resolved, however when we put down a new solid wood floor, we have noticed that the planks near the base of the chimney have started to warp and separate. I assume there must be moisture on the floor under these planks, these board were not secret nailed but glued as they were laid on the old tiles from the 1920's fire place, the rest of the flooor is secret nailed to the existing pine floor and is fine.

Again before I bought the house, the Chimney stacks was removed at roof level but the chimney breasts still remain, there is a vent in the chimney breast on the ground floor but there does seem to be some moisture around the vent, but otherwise the chimney breat is dry.

Can anyone provide me with possible causes of the damp floor or steps that I should follow to help me workout where the moisture is coming from. I was going to start getting a roofer to check the roof where the stack had been removed. but i thought i wouls see damp upstairs if thier was a problem.

From the research i did on the internet the possible cause could be condensation in the chimney. so i was thinking of increasing the size of the vent.

I did lift the floorboards up before i get the flooring laid to check for dampness but it looked fine underneath. The walls either side of teh chimney that had the DPC seem ok now.

Any help/advice would be greatly appreciated.

[welsh brickie]

it could be poor underfloor ventilation,there could be water in the floor space after heavy rain, moisture can be trapped causing condensation.You can hire a borescope (camera) to check under the floor.
Extra airbricks would solve the problem.

[nks2008]

Thank you for your help, it make sense now i think. I remember the whole pine floor being slightly damp before the wooden floor went down.

I will add a couple air bricks, and se iof that makes any diffrence.

once again thanks for you advice.