I have used a cheap sketch book (bought from The Works for just 99p) for the tar paper cladding. The paper is quite thick and takes PVA glue well. I have cut the paper into scale widths and torn the edges to simulate the wear and tear seen on the original (see earlier post). Once the paper was in place, I painted on another watered-down layer of PVA glue and acrylic texturing paste to ensure it would not peal off and add some additional surface texture.
The image below, shows this in greater detail.