Lets say that some kind of long term SHTF happens, like what happened in 1348 with the Black Death. Large areas are depopulated, nobody is around to maintain roads, nobody is around to keep the trees cut back, or do maintenance on buildings. What can we expect? In an effort to what what will happen to our infrastructure, my wife went driving around to look at abandoned sawmills and abandoned sawmill towns.
A local sawmill burned down in 1925, was not rebuilt and the land was abandoned in the 1930s or 1940s. All that remains is a couple of walls, the foundations, and some motor mounts where the saw motors were bolted down. If it was not made of cement or steel, its long gone. But even then, the steel is starting to rust away. Nothing of wood is visible above the layers of leaves and pine straw.