Solid Hardwood, Engineered and Laminate Flooring - Leveling a floor for Laminate

I live in an old carriage house that has a basement slab that falls 3" from the back wall to the front. I guess they wanted the water, ice and snow from the horses to drain out to the front. The horses are long gone and now I want to level it to make a family room and install an engineered floor.

Someone suggested building it up with PT screens with plywood. Another said use a sand mix concrete and level it. I saw these 2 by 2 squares with plastic bottom on them at Home Depot. You just add additional plastic pieces to make it level. Any other suggestions? Thanks, Jethro-Buckeye

You need to do a moisture test on the concrete to assure that you will not have moisture issues. You will need to install a vapor retarder over the concrete. Then, you can rip 2x4's to accommodate the height difference in the floor and to act as sleepers on which you install a plywood subfloor for your flooring. The subfloor must be flat to prevent flooring failure.