You will have to make sure your joists can handle the addition of considerably more weight from the plywood subfloor and any floor coverings.
How to level floor for rugs.
Then mix leveling compound according to the instructions on the package in a large bucket.
Lay a long level downhill on the floor with one end of the level on the level part of the floor and the other end at the lowest point.
Installing carpet pad over uneven subfloors or floating floors over uneven subfloors will only cover up the problem temporarily.
You need to fix the uneven floors by using a leveling agent or putting down a new subfloor.
Learn how to coordinate rugs in an open floor plan.
Work your way outward from the interior of the room.
Raise the lower end of the level until the bubble is centered then measure the distance from the bottom of the level to the floor to find the depth of the dip.
On the top side of the floor another fix it idea to lay down new hardwood over the existing floor.
A plywood subfloor will bridge any minor waves in the existing floor and leveling compound would help too.
Once the compound reaches a creamy consistency pour a thin layer into the sunken sections then smooth out inconsistencies with a hand trowel.
The carpet pad over uneven subfloors will wear unevenly and quickly with the pressure from feet and furniture causing the carpet and the padding to wear out much quicker.
Cover ugly floor tiles instead for an easy inexpensive new look for your home.
My dining room is open to my living room office kitchen and entry way.
Place several throw rugs around the room or cover up as many tiles as possible with one large area rug.
To level a floor start by removing the existing flooring.