I have lifted the floorboards along a spare bedroom wall to find the cause of mould forming on the wall and discolouration of the carpet.
I discovered the ends of some of the joists were dripping with water but the mystery is they are short of the wall by about an inch but supported by a sleeper running parallel to the wall about 9 inches back and the 4X2 plate on the sleeper is dry with a good dpc on the brickwork. The internal wall is also dry even below the dpc.
My only theory for the cause of this is that there is an air brick below the affected joists and moisture in the atmosphere outside could be resulting in a capillary action in the end of the joists.
Has anybody out there experienced a similar problem to either confirm my theory or blast it out the water? Literally!!!!
In the meantime I'm going to dry out the ends and give them a good coat of bitumen.

odd one...
airbricks are designed to allow air into the floorspace, at opposite sides of the house creating an 'airflow' that will stop moisture collecting...
without knowing the details regards this I couldnt comment further, suffice to say that the area beneath the floorboards should be well supported, well ventilated with enough clearance from soil / ground...
with regard to the joist ends, I'd say treat them with a rot treatment as opposed to bitumen, let them breathe but kill any rot that may have occured or youll just seal any moisture in...
some photos would be helpful...

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http://www.peterborough-plasterer.co.uk/

Yes it is an odd one. That's why I called it a mystery.The floor meets all the requirements ie.
airbricks and air flow, well above ground level with good support and the main length of the joists are bone dry. It's just the end 6 inches of 2 of the joists which as I said are not into the wall.
I have left the boards up for a while and they are drying out well so I will keep an eye on it.

Thanks for your interest

just a thought...
you sure there isnt a leak somewhere alont the line of the supporting joist? and the waters tracking along it wetting the ends? still an odd one but im just thinking of possibilities? or water getting in from outside somewhere and tracking?

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http://www.peterborough-plasterer.co.uk/

Thanks for your thoughts but the only pipes under the floor are for the
radiator which is 12 ft away and running paralell with the joists. Not only
that but any leak would show in the drop of pressure on the boiler