Should a vehicle floor be laminated

Underbody protection for the caravan: care tips and tricks

Browsing the Internet doesn't always help. Anyone who would like to know whether, how often, and with what to rework the underbody protection of their caravan, will encounter a lot of well-intentioned advice - and no less numerous controversial opinions.

Dieter S. Heinz, Corrosion Protection Depot, Archive
If nothing is done for a long time, considerable damage can occur.

And the operating instructions from the caravan manufacturer are only of limited help. Bürstner and Dethleffs, for example, remain vague: "The underbody of the vehicle is partially coated with age-resistant underbody protection. If the underbody protection is damaged, repair it immediately." And further: "Only use products approved by the manufacturer." The customer should get advice from trading partners and service centers. However, there is agreement on this statement: "Do not treat surfaces that have been coated with spray oil." However, there is also manufacturer information in which the underbody protection is completely ignored.

These sub-floors exist

Nowadays two different floor constructions are common: the classic one Wood sandwich constructionthat relies on a protective coating, and the more modern and easier to care for GRP construction. The same applies to both: the base plate must be light, it should be robust and durable.

Dieter S. Heinz, Corrosion Protection Depot, Archive
The classic sub-floor: plywood panels, wooden strips, EPS styrofoam insulation and underbody protection.

Wood sandwich construction: The classic meets these requirements with a wooden slat framework, which is lined with EPS styrofoam panels and glued inside and out with a poplar plywood panel about six millimeters thick. On the inside, the PVC plastic flooring is also put into the press, and a breathable, because surprisingly thin, layer of underbody protection is then applied to the outside.

GRP floor constructions: They are becoming increasingly widespread. They completely dispense with wooden slats as carrier material and the outer plywood panel coated with underbody protection. Instead, stabilizing struts made of lightweight and stable PU material are inserted. Closed-cell XPS foam is often used as the insulation material, which, in contrast to the previously used EPS panels (commonly known as Styrofoam), does not absorb any moisture. The end to the outside is a 1.5 millimeter thick, but all the more robust plate made of fiberglass. GRP is particularly resistant to mechanical loads such as the effects of the weather.

Inspections help with maintenance

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Suspicious areas are examined with the moisture meter as part of the leak test. This is the only way to track down ailing areas.

Regular checks are important, regardless of the floor construction. In the first few years this is done as part of the tightness guarantee. Later, a regular check-up is advisable at least every two years. As part of these tests, the underbody protection layer is usually also selectively refreshed - at least at critical points such as joints or wall transitions.

Very important: Damage caused by stones or other sharp-edged objects should be repaired as quickly as possible. Because penetrating water can - especially with conventional wooden floor constructions - cause considerable long-term damage. The same applies if nests of dirt accumulate on tight-fitting aprons, crevices or openings that store moisture for a long time. And that allows exposed wood to rot in the long term.

GRP floors are not quite as susceptible, but cracks or even holes in the fiberglass, which are not only superficial, also have to be repaired here. This is done by a specialist who repairs the damaged area by lamination and, if desired, paints it in for the sake of appearance. According to customer service experts, the additional use of underbody protection materials is not necessary for GRP sub-floors, not even on joints or breakthroughs.

Materials used at the factory for underbody protection of caravans can be easily refreshed. A complete, large-area subsequent treatment of the entire subfloor is, however, generally not necessary. On the contrary: Just like with the leak test, it is sufficient to inspect the critical areas, knock off suspicious areas and examine strangely dull-sounding areas more closely. The same applies to areas where the existing protective layer is peeling off or bulging. Here, too, you have to react quickly before the damage becomes greater and therefore more expensive.

Standard underbody protectors are useless

With regard to the means to be used, adventurous recommendations are sometimes circulating. Standard underbody protectors that are used on the painted floor pan of cars, or even simple wood protection glazes from the hardware store, are absolutely unsuitable - even if some online people claim otherwise.

The protective layer applied by the manufacturer to caravan wooden floors is usually diffusion-open and water-repellent, similar to the membrane of a good rain jacket. And the funds subsequently used should also do that. Only then can the humidity stored in wood and insulation material due to temperature differences evaporate again to the outside. There are special bitumen-based products from Elaskon (Caravan C-UBS, 1 liter spray can, around 20 euros), from Dekalin (Dekaphon 9735, 500 ml spray can, around 20 euros) and the naphtha-based, which is also vapor-permeable Funds for the specialist workshop called "Underbody Protection Special" from Würth.

If you want to improve or repair the underbody protection yourself, you should definitely study the processing instructions in advance. The surface must always be clean and free of grease - and above all, really dry. It is ideal if the caravan can be parked in a dry, well-ventilated hall for a few days before treatment. Always shake the spray can well for a few minutes before application and then apply the underbody protection in thin layers. Caution: Under no circumstances should the intake port of the heater be covered with spray mist. In this way, every sub-floor retains its supporting role in the long term.

means for the purpose

Dieter S. Heinz, Corrosion Protection Depot, Archive
KSD coating resin is highly hydrophobic and even displaces moisture from wooden floors. It is mixed with hardener and used to repair damaged or ailing areas.

Special products for the subfloor must be suitable for caravans and must not attack the existing protective layer, sealing compound or the insulation of the floor construction. Owatrol oil is highly hydrophobic and will displace moisture even from wooden floors. The ideal basis for a successful repair. The same applies to KSD coating resin, which is mixed with hardener and used to repair damaged or ailing areas. Finally, the special bitumen-based caravan underbody protection from Elaskon seals repaired areas, provides reliable protection against stone chips and corrosion and is compatible with the material already applied at the factory.