We raised the roof on our cape cod and extended the 2nd floor by 6 feet above the garage. This 6 foot section is not level with the existing subfloor. It slopes from 0" to 1/2" over the 6 feet. What is the best way to make this area level with the existing sub-floor so I can install hardwood flooring? Do we just use multiple layers of Rosin paper? Is there a compound that can be trowled & leveled? Or do I have to rip-up the sub-floor and shim it? AI appreciate any suggestions.