Greetings,

Although a lifetime DIY'er, this is my first floor and I've read hundreds of posts here and have come up with a plan of attack which I'd appreciate comment on before I get too deep into this. First some background.

Current kitchen floor is 6" red oak planks, tongue and groove with no subfloor (125 year old house). Lots of joist settling, etc. I plan to install a floating laminate "wood look" floor over this. I want to minimize transition heights to adjacent rooms so would like to add minimum additional underlayment. Floor will have hydronic radiant heat, using underfloor hung piping system in joist bays below (full unfinished basement below). Here's my plan, please feel free to comment liberally.

1. HVAC contractor is moving some heating pipes so I can install a beam underneath to cut the span from 15' to 7.5' to add rigidity. Will also jack the beam a little to try to raise the floor (low spots primarily in the middle because of sagging and cracked joists. Will sister or replace cracked joists duringt his phase also. Goal is to get floor as "flat" as possible during this step. Currently has "swales" as large at 1.5", as said, primarily in the ccenter.

2. Will then screw down all the current 6" planks to affix them solidly to the joists (they are fastenen with cut nails and have a lot of movement.

3. As this stage, I am a little confused. I was planning to lay down about 1/4" of something (plywood, concrete board, whatever is best) but also assumed I would still need leveling and would have to apply planiplex or something else to get withing 1/8". Do I put the underlayment first and then planipplex, or the leveling compound first and then underlayment?

4. Finally I was going to float the floor. HD conveniently stacked rolls of "foam" underlayment next to the flooring, so I bought some. Do you recommend using this? there is no foam backing on the laminate planks. I am assuming if I use this, I don't need to put down any vapor barrier?

5. Final question for now :):)... Never having used this type of floor before maybe this is a stupid question, I am assuming that flooring does NOT go under cabinets but does go under dishwasher, stove, fridge etc. Thus should I add another layer of 1/4" or 3/8" plywood under the cabinets to get them to the same level as the foam and flooring? Also, between kitchen island and main cabinets, will be 42"-48" of flooring running parallel to island, is the weight of the floor enough to keep it down? Meaning, will it feel "spongy" in the narrow areas, or is this all part of making sure I'm withing 1/8"?

THanks you for all your help!!!!