hi Albert
the norm with dry rot is fungus and some sort of root growth, and when disturbed it will fruit and release a powder which is very much like paprika to look at, we are sovereign approved installers and we still send samples off to their labs to make sure we have diagnosed the rot correct, as more often than not it is just wood rot ,if you think it was dry rot then the whole area should be treated even the walls, make sure you have good air flow in the floor void
all the best with the refurb