I have a floor joist that is sagging where a knot has split open.

The problem: it is directly over my furnace.

The other problem: I cannot get access to the joint on either side of the split because the duct work comes off the furnace and raises to about 2 inches under the joist.

The 3rd problem: my home was built in 1949 (very solid) and has insulating tape around duct joints; therefore, there might possibly be asbestos issues.

I feel comfortable fixing the joist using the sister method, I just need to figure out how to jack the joist up with all the junk around it.

Is there some material strong enough (for 2 inches worth of clearance) that will allow me to use a jack on both sides of the joist to lift it up long enough to sister repair the joist?