Complex sentence: Aluminium has considerable advantages over wooden masts, being lighter, stronger and impervious to rot; further, aluminium can be extruded as a single piece for the entire height of the mast.
Split into simpler sentences: Aluminium has considerable advantages over wooden masts, being lighter, stronger and impervious to rot. Also, an aluminium mast can be extruded as a single piece for the entire height as the mast.