I have a floor joist that is sagging where the joist was drilled
through to allow for passage of the hot water heat pipe. Naturally
this hole was made in pretty close to the exact center of the joist
and they never sistered it as they should have done to begin with. To
make matters worse, the previous owner had a grand piano sitting on
this spot.

There's no splitting or cracking, but the joist is clearly sagging
about 1/2" in the middle. It's the end joist, and the floor has
settled enough that the quarter round now dips slightly below the
baseboard.

I've jacked up and sistered rafters before but am a little unsure how
to approach this since the hot water pipe runs directly under the
joist preventing me from jacking up the joist directly.

Is it acceptable to lift the joist with a sistered member attached to
the half of the joist with the pipe and then fasten it to the other
once it comes up to level? If so, how do you gauge an appropriate gap
on the new member so that you can jack it up correctly?

Thanks for any advice. We moved some furniture around so that it's
visible and it's driving me crazy.