After decades of walking through homes and casually advising that lowered floor levels (aka sunken living rooms, dropped floors, conversation pits) can be filled in with concrete or a wooden subfloor, I finally filled in an area in our home! You may recommend having a space filled but if you are lucky you mention it to your favorite general contractor and voila! On the next site visit, it is finished!
We moved the furniture out. The general contractor and concrete sub coordinated the work. We ordered a new door. When it arrived, the sub installed a rebar grid for support. Then the concrete truck arrived (at 5 am!) and the pour began. Several people smoothed and leveled for a couple of hours. (The timing depends on moisture and other variables.). The surface dried untouched for a few days. After a week, tile was installed under the beverage chillers. We rolled out the old carpet as we had just rolled it and slid it to the patio. The footprint of the old carpet was the same so we put the padding strips back and rolled it back in. This makes it convenient to wait a while so the concrete can thoroughly cure prior to wood installation. That installation can be done at our convenience.
The tripping hazard was eliminated and aging-in-place ensues!