Dry rot?

[Dwalker96]

After a little bit of diagnosis/advice please.
In our Victorian property, we have uncovered some rot in the staircase timbers (underneath the bottom 2 steps). The timber is very crumbly in places, but it seems to be on the surface rather than all the way through, and areas such as knots are solid. It also affects several timbers in the area, including those not in contact with the ground. There was red/brown dust on the floor beneath the timbers, but no mushrooms/dry rot fungus I can see not any smell. There are what looks like cobwebs but not sure if this could be hyphae. Any ideas? Thanks!!

 

[Dwalker96]

Images

 

[Lower]

Looks like you have had some woodworm at some point and a water leak that has caused wet rot.

 

[Deluks]

If you can access it, poke it with a flat head screwdriver, to see how much resistance there is in the middle of it.
If it's relatively sound on the inside, treat all timbers with wood preservative and monitor.
If it's completely shot, then best to replace it, although access could be awkward, it's no fun doing woodwork whilst lying on your belly!