So I’ve been working in this house for the last few weeks on and off and I’ve found multiple rotten joists in the floors /ceilings. Finally cleared out the rubbish by way of 4 12 yard skips and started removing the damaged floor boards in the front room and found this on the underside of several boards . I think it’s dry rot but not sure . I have silka 5 star wood treatment which I’m hoping will protect the rest of the timber from further damage. Tia