We started a project today at a home that has a 320 sq ft sunken living room.
The concern was injury from flalling because of an unexpected step down that no one expects!
We first had to determine the depth we needed to raise the floor and decided to start with 2×4 framing.
We laid out the floor like you would lay out a framed stud wall but also used concrete screws to insure movement would be limited.
After framing the floor, we used decking adhesive and installed 3/4 inch decking.
After the decking, we added another layer of 1/2 inch OSB and it was also glued down. This added strength and got us to the correct height.
Personally I was thinking of installing a goldfish pond and a fountain, but they would lose their living room…. Oh well… It was a good thought…
Stay tuned… Tomorrow we install laminate flooring on top of the new decking!
Renov8z 
Hello, I have a sunken kitchen, wondering what the cost of this was?
This particular one cost 1600 which included labor to install the frame, decking, underlayment, and laminate flooring. We also removed old carpet and added new trim and transition strips. Of course every one is different, so we would have to see it.
Thank you! Ok well we’re in San Diego and gonna be doing it ourselves and that number is definitely doable! Thank you for the post! Before I found this, we were just gonna pour concrete.
Good luck with it!