I live in Houston and have an unfinished little house in my backyard. This little house has always been studded interior only but brick veneer with a metal roof. For the past 23 years, we have used it as a shed/storage area but now want to finish it for an apartment for my retired in-laws.

The metal roof and the old wood siding were replaced a few years ago with a new metal roof, double-paned windows, and vinyl siding to replace the wood. We also removed the cupola/squirrel house to close in the roof completely.

The sill plate has almost completely rotted in most areas as we have flooded 4 times and the house has always been so full of stuff we couldn’t see the walls. After a complete cleanout, we also noticed that the sheathing between the brick walls and the studs has either completely crumbled away or is in the process of doing so. 

My question is how do we replace that sheathing and the sill plates?