I build my layouts using the L-girder framework and a torque-less power screw driver. Nails are never used and glue is used only in problem areas. When it comes time to move or just redesign, remover buildings, track and screws. Almost all of the girders, beams, uprights and cross braces can then be used again. Good wood (and I would only use good wood on a layout) is too valuable to be cut-up and thrown in a dumpster.
There is no such thing as a permanent layout.
Happy railroading,
Don