How To Raise The Floor Level . If there's a lip you can sand it until the transition is smooth, or by adding a leveling compound. Using chalk or a pencil, mark low and high points and check again for any ridges or depressions you. Garage Remodeling Converting a Garage Into a Room from www.budgetdumpster.com Raising a garage floor to house level with pressure treated 2x6 joists, midspan blocks and plywoodto convert into a bedroom, home office or any living space. Adding a layer of 5/8 plywood should work to raise the floor that much. Clean out any cracks with a wire brush.