Advice needed! Joist in bathroom subflooring appears to have wet rot... repair needed??

[Markos88]

Hey all. This is my first post here. Got the keys to my new house about 6weeks ago. Took up some of the chipboard flooring in the bathroom a few days ago as it was clearly water damaged most likely from water that had penetrated through the tiles where the shower was.

The rot on the joists appears to have originated exactly where the nails in the chipboard flooring were located, nearest to the wall. I’ve shown one photo of the worst rot to my uncle who’s a veteran plumber, and he’s suggested I need new joists. He’s interpreted the photo as if the rot has penetrated the end of the joist due to it not having a waterproof membrane on it. I think he might have misinterpreted the photo though. I feel fairly confident that the rot originated where the nail was and penetrated the joist along the nail puncture. The end of the joist appears to be unaffected lower down, I think it’s only the top part of the end, which suggests to me that the source of water maybe hasnt come from damp in the cavity?? More likely that it’s originated from the nail puncture and has travelled along the grain towards the end due to osmosis forces??

What’s everyone’s thoughts? The rot seems to go about 2cm deep into the top of the joist. I’ve gave it a lot of thought and googled a lot. All the examples I’ve come actoss where the joists have been repaired via sistering were a lot worse than my joist. I’m currently looking into buying epoxy resin to fill the void in the joist once I’ve brushed out all the remaining flaky soft parts, just to help the joist regain some of it’s strugtural integrity, though most non-proffesional people I’ve asked have said it should be fine as it is as long as I’ve resolved the source of the water issue.

Thanks in advance. If I can give any more info that might help with the advice, let me know.

(ps. the rot in the worse-off joist appears to be deeper in the photo than it actually is because the breezeblock mortar covers some of it’s height near the bottom... joist is 8inch in height)

Thanks a lot,
Markos

[Ken010]

Have seen loads of very, very much worse cases than indicated in your images.

Can I suggest you get a thin long probe? A screwdriver or similar and push it into the areas of concern? just to see how far in it manages to get, any further images would be of use of the above?? If possible??

Ken.

[aeromech3]

Have you looked at this video which will give you some idea what is 'permissible' in joists I would not expect epoxy filler to add to the strength, it is a filler but it will at least stop puddling if there is any subsequent leaks. Clean out the rot and use something like Ronseal Wet Rot Wood Hardener.
https://www.youtube.com/watch?v=y7QSTOTMymU

[wes56]

As suggested above, you should force a small screwdriver into top and sides of all the joist tails that are going into that wall - any, and all, rotten wood to be chiselled out.
If you begin to remove the majority of a joist section then photo it and post on here.