There.

[desperance]

Acting under instruction (thank you, instructive friends!), I have duly ripped out the nasty and disposed of same into the back alley, whence it will mysteriously disappear.

If I had done this fifteen years ago, I would have had attractive exposed boards all this time, and very possibly not rotten joists beneath them.

I suppose we live and learn. I do kind of feel I could have lived without this lesson.