Building a camper van floor: construction and materials

A typical camper van floor consists of these layers from bottom to top: 1. The metal van floor is the original floor of your van. Clean it thoroughly and treat any rust spots with rust converter and primer. 2. Sound deadening (optional): a layer of bitumen or butyl rubber (e.g. Silent Coat, Noico) on the bare metal reduces vibrations and road noise. 2-3 mm thick, 1-2 kg per m². 3. Insulation: XPS boards (20-30 mm) are most suitable for floor insulation. XPS is compression-resistant, moisture-proof and doesn't absorb water. Lay the boards over the ribs so any water underneath can drain away. 4. The structural board is 9-12 mm plywood as a base for your furniture and floor covering. Poplar plywood is the lightest (~400 kg/m³). 5. The finish layer is vinyl, PVC click flooring or rubber flooring. Choose something waterproof, wear-resistant and easy to clean. Total build-up height: 35-50 mm. Factor this into your standing height!

For floor insulation, XPS (extruded polystyrene, e.g. Jackodur, Styrodur) is by far the best material: • Compression-resistant: XPS can handle 20-70 tonnes/m² without collapsing. You can place heavy furniture and batteries on it. • Moisture-proof: XPS doesn't absorb water (closed cell structure). Crucial for a floor where moisture can come from below. • Good insulation value: thermal conductivity (λ) 0.029-0.036 W/mK. 30 mm XPS gives R 0.86. • Easy to cut with a utility knife or fine-toothed saw. Armaflex is less suitable for floors because it's not compression-resistant. Use Armaflex for walls and ceiling, XPS for the floor. Lay XPS boards loosely (not glued) over the ribs of the van floor. Fill gaps with PU foam. This way, condensation that gets under the insulation can drain through the original drain holes in the van floor.

On top of the insulation you lay a structural board as a stable base: Poplar plywood is the lightest option (~400 kg/m³). 12 mm thick is sufficient as a base. A sheet of 250×122 cm weighs ~15 kg. Ideal when weight is an issue. Birch plywood is stronger and harder than poplar (~680 kg/m³), but also heavier. 9 mm birch is comparable in strength to 12 mm poplar. More popular with professional converters. Moisture resistant? Choose plywood with WBP glue (Water and Boil Proof). Standard interior plywood can swell with moisture. Fix the structural board with stainless steel screws through the insulation into the ribs of the van floor, or use construction adhesive. Pre-drill with a thin bit to prevent splitting. Tip: mark the position of the ribs on the structural board before screwing. This way you know exactly where you're screwing into solid metal.

1. No rust treatment: if you don't treat the metal floor before insulating, rust develops invisibly underneath. Use rust converter on rust spots and apply a coat of primer. 2. Blocking drain holes: the original van floor has drain holes for water. Do NOT seal these. Water that gets under the insulation (condensation, leaks) needs to be able to drain. 3. Armaflex on the floor: Armaflex is not compression-resistant and gets squashed by furniture and your own weight. Use XPS for the floor. 4. Structural board too thin: 6 mm plywood flexes under heavy loads. Use at least 9 mm (birch) or 12 mm (poplar). 5. Forgetting standing height: 40-50 mm floor build-up costs standing height. Measure your standing height after both floor and ceiling finishing. In an H2 van (1.90 m interior) after floor (45 mm) and ceiling (25 mm insulation + 6 mm board) you'll have about 1.82 m left. Cost: budget €200-€300 for a complete camper van floor (sound deadening + XPS + plywood + vinyl). Time investment: approximately 15 working hours.