The smallest and lightest caravans, such as an Adria Altea, have a weight of around 900kg and a Maximum Technically Permissible Laden Mass (MTPLM)of 1100kg. Generally, trailers below this weight don't have toilet/shower facilities and are really camping trailers more than a common understanding of what a caravan provides. The heaviest caravans you will see on UK roads would be something like a twin-axle Airstream International. The weight of these caravans unladen is around 2,000kg and with an MTPLM of around 2,400kg.