strange rot in timber joists.

[fin]

ok.... ive been a joiner for a while now.... im 41 years old. in my time ive repaired a fair few floors cutting back rotten joists and sistering up joists to the side of them.

today i was called by a friend of mine who runs a flooring company in sunderland. few rotten floor boards in the entrance to a house. so i called by as i had a free day due to bad weather. (that ended up being not bad.... fecking wether forecasts )

pretty standard repair im sure i cut back the rotten joists to what i thought was a decent section of timber. but while cutting i could feel in the saw that i wasnt cutting particularly decent timber... like you know how the saw behaves if youve done it before i guess. the timber seemed to be rotten on the inside but reasonably solid on the outside.... certainly given that half of the floor has been covered with a new lvt floor its a bit too late to rip it all up to replace it.

[fin]

so the last pic was my first cut. the second pic is the other part of the first cut and the first pic was when i cut another approx 6 inch off. that part of the joist left in the building was still reasonably solid. like i said im limited as the rest of the floor has already been covered so replacing the joist isnt really an option..

i havent drawn around the rot with a pencil even though it looks as if i have,

like i said ive never seen anything like it before..

[fin]

the reason for me being called into this job was that the joist ends had rotted, i ended up cutting about a 1 meter back from the rotten ends.

[Grendel]

I had over thirty years in restoration so I've seen a fair bit of rot. I have seen this sort of thing before although as to the reason I'm not sure. Best explanation I've heard was that the timber was wet and of course the outside dries quicker so fungus follows the moisture which would be in the centre or thereabouts of the timber. Might be twaddle but I haven't heard a better idea.
I've seen it almost to the surface and have also seen a similar sort of thing with woodworm where the outside of a piece of timber looks unaffected.

[aeromech3]

To me it looks like a fungi started when the timber was still a tree.