Resolving black mold, grey fur and general wetness in bathroom floor joists

[Oldman]

I think I need some advise please, I looked up at the outside wall of the ground floor kitchen to see water stains on the wall and ceiling. Ive lived in this house since 1975 and Ive never had a leak upstairs in all that time.
The bathroom directly above has fitted carpet and fitted basin vanity unit with no evidence of water in wrong places, so tonight has been carpet up, floorboards of course go under the vanity unit and toilet so out came the saw. The boards are T & G of 1962 vintage so the cut nails fought back some.
Once I had a long board up I can see staining and black mold around three 8" x 3" joists from the wall back 2ft into the room.
Tomorrows job is to remove the vanity unit and see if its the waste and or a supply pipe leaking, but it must have been doing so for some time I would think to get such a growth.

So, I will of course fix the leak but how to I treat the timbers to remove the mold and fur? Do I let them dry out on their own or force dry in order to rebuild the bathroom before next spring!
I retired 10yrs ago expecting things to get easier, I'm still waiting on that!

 

[Bingy man]

I think I need some advise please, I looked up at the outside wall of the ground floor kitchen to see water stains on the wall and ceiling. Ive lived in this house since 1975 and Ive never had a leak upstairs in all that time.
The bathroom directly above has fitted carpet and fitted basin vanity unit with no evidence of water in wrong places, so tonight has been carpet up, floorboards of course go under the vanity unit and toilet so out came the saw. The boards are T & G of 1962 vintage so the cut nails fought back some.
Once I had a long board up I can see staining and black mold around three 8" x 3" joists from the wall back 2ft into the room.
Tomorrows job is to remove the vanity unit and see if its the waste and or a supply pipe leaking, but it must have been doing so for some time I would think to get such a growth.

So, I will of course fix the leak but how to I treat the timbers to remove the mold and fur? Do I let them dry out on their own or force dry in order to rebuild the bathroom before next spring!
I retired 10yrs ago expecting things to get easier, I'm still waiting on that!

A very small leak that goes unnoticed for years does far more damage than a sudden leak or burst pipe . In the event you don’t find anything leaking inside Make sure all your gutters and any roof valleys are in good order , all external drains are working and not blocked . A good roofer is advisable- Back to inside and check everything use a good light and if necessary run the water in the bath , basin, shower etc . It could be as simple as the seal around the bath or shower . As for the mould then assuming you have corrected the root cause then letting it dry out is key . Leave the problem area exposed if possible ( if safe to do so ) to allow warm / dry air to circulate. Dehumidifier can help the drying process. If the affected timber is sound and not rotten then my choice would be sika 5 star complete x 2 coats to all affected areas. There are others such as everbuild but I prefer sika.