Double floor

A double floor is a motorhome body design with a 10–25 cm technical cavity between the outer underbody and the inner floor. The cavity houses fresh and waste tanks, batteries, heating ducts, and heated pipework. Standard on premium European motorhomes built for year-round use.

Advantages: water and tanks stay frost-protected down to −20 to −30 °C with heating on, a lower centre of gravity, and large extra storage volume. Drawbacks: 150–300 kg of extra mass and a step-up floor (+25–35 cm). Well-known double-floor builders: Concorde, Frankia, Niesmann+Bischoff, Carthago liner-for-two, premium Knaus models. Not the same as a simple insulated floor, which has no usable cavity.