Under the wash hand basin in an old sandstone house by the sea a couple of narrow floor boards have disintegrated with rot when I removed them there is a little rot in the Joist end perhaps only what would be expected in a house over 100 years old but as a new bathroom is to be fitted I thought I would ask some advice thank you
See the project on the website called repairing structural timber. It would be a good idea to replace the rotten end of the joist. Its not a huge job and it will not get better on its own. It will also help you if you decide to sell.