Welcome to Frog Forum Tidal! Are you in the UK? Ask because visited the VivExotic site and those vivariums are made in UK. From there website read they are made from processed chipboard and laminated with melamine (a plastic). They do recommend that you seal your vivarium with silicon once constructed to prevent chipboard from swelling and make it waterproof. Have not lifted one; but in my experience all processed wood products are heavier than natural wood of similar size and thickness.

Glass made terrariums like Exo-Terras are sturdy, relatively lightweight (compared to same size glass aquariums and wood vivariums), and can even hold a few inches of water if desired. They do cost more but sometimes can be bought on sale or maybe find a used one in good condition. Good luck!