Damp in a caravan or motorhome – causes and solutions

Are your windows misting up, does your caravan smell musty after winter, or do the cushions feel damp? Moisture in a motorhome or caravan can be caused by condensation, inadequate ventilation or water entering through leaking seals. Start by finding out where the moisture is coming from. Repair leaks and check the ventilation before choosing a dehumidifier. If humidity remains high over time, a correctly installed desiccant dehumidifier can help, especially during storage in cold conditions.

Find the right dehumidifier

How can you spot damp in a motorhome or caravan?

When you open the door after a few weeks without using the vehicle, a stale smell may be the first thing you notice. Look out for:

• Misting and condensation on windows, frames and cold surfaces.
• Musty smells in cupboards, under beds or behind cushions.
• Stains, bubbles or peeling finishes around rooflights, wall joints and windows.
• Soft floors or damp fabrics that do not dry out.

A little condensation after several people have slept in the vehicle does not necessarily mean there is damage. But stains that spread after rain, soft flooring or a smell that keeps coming back should be investigated. Also check beneath mattresses and inside storage lockers. Read more about signs of moisture damage.

How to measure moisture levels

A hygrometer lets you track temperature and relative humidity, for example after a night in the vehicle or during storage. Take several readings: one high measurement does not tell you whether a material has been damaged. A moisture meter for materials is used to investigate moisture in different materials, but the result depends on the method and material. If you suspect hidden damage in a wall or floor, ask a workshop or inspection company experienced with leisure vehicles to carry out a damp inspection.

Why does moisture build up in caravans and motorhomes?

In a small space, cooking, showering, drying clothes and sleeping all release a considerable amount of water vapour. When warm air meets a cold window or outside wall, moisture can condense into droplets. Ventilation must therefore work even when it is cold outside.

Water ingress is a different problem. Ageing seals, roof joints, openings, windows and leaking water installations can let water into the structure. A localised stain that reappears after rain is an important clue. A dehumidifier can lower air humidity, but it cannot stop water from continuing to enter.

Both motorhomes and caravans can be affected. In a motorhome, also check the junction between the cab and living area. In a caravan, roof seams, corners and the floor deserve particular attention. The vehicle’s condition and seals matter more than whether it has an engine or is towed.

Three habits that help during your travels

Ventilate after cooking or showering. Use the existing roof vents and air the vehicle briefly when outdoor conditions are suitable. Do not leave moist air trapped inside all evening.

Check behind mattresses and cushions. Condensation can form where warm indoor air meets a cold outer wall, out of sight from the seating area. Lift cushions and allow damp surfaces to dry.

Deal with wet clothes. Rain jackets, swimwear and towels add a lot of moisture to a small space. Dry them outside the living area where possible. Never block ventilation openings to keep the heat in.

How to prevent damp during winter storage

It is easy to assume the vehicle will look after itself while parked up. But rain, snow, melting water and changing temperatures can cause problems even when nobody is using it. Before storing your motorhome or caravan:

1. Inspect the exterior. Check the roof, windows, hatches and openings. Repair suspected leaks according to the manufacturer’s instructions.
2. Store the vehicle dry. Dry wet surfaces, clean the interior and, if possible, take cushions and textiles home for dry storage.
3. Winterise the water system. Drain and protect pipes, tanks and equipment in accordance with the vehicle manual.
4. Allow air to circulate. Open suitable cupboards and compartments, but never block normal ventilation or gas safety vents.
5. Check on the vehicle. Inspect it after heavy rain and throughout winter to spot new stains or smells early.

Moisture-absorbing sachets can help inside small cupboards but have limited capacity. They cannot replace ventilation, repairs or a dehumidifier if the entire living area experiences persistently high humidity.

For vehicles stored outdoors, keeping roof drainage and seals in good condition is particularly important. A cover must not trap moisture against the surfaces; follow the manufacturer’s advice on suitable protection and ventilation. If the vehicle is kept in a storage building, you also need to know whether it is heated, ventilated or damp during winter.

Which dehumidifier is suitable for winter storage?

A condensation dehumidifier cools the air so water collects in a tank or is drained away. It can be suitable in heated spaces, but its capacity often falls as the temperature drops. A desiccant dehumidifier instead captures moisture in a rotor and expels it as moist exhaust air through a duct. This makes the technology useful even in cool vehicles. The right choice depends on temperature, air volume, moisture load and whether the equipment can be installed correctly.

If you only get brief condensation after an overnight stay, start by improving ventilation and daily habits. A dehumidifier becomes more relevant when you have monitored humidity over time and it remains high even though the seals and ventilation are working properly. It must have a safe power supply and a safe way to discharge moisture while the vehicle is parked.

EvoDry 6H 2.0 for motorhomes and caravans

Our EvoDry 6H 2.0 is a compact desiccant dehumidifier designed for applications including caravans and motorhomes. It has a humidistat that controls dehumidification according to the selected setting. Moisture is expelled through a wet-air hose rather than collected in a tank that needs emptying.

Plan the installation carefully. The dehumidifier must be stable and have unobstructed airflow, and the moist exhaust air must be discharged outside the space. Installation inside a cupboard requires sufficient air circulation, access for servicing and correct hose routing. Follow the installation instructions and check that the electrical connection meets the requirements of both the vehicle and the product. Do not make openings that could damage weatherproofing or safety ventilation. The dehumidifier must be checked and maintained as specified in the manual, even during long-term storage.

If moisture damage has already occurred

Have the walls or floor become soft, or have you found suspected mould growth? You need to find the leak and have the damage assessed. Damaged materials may need drying or replacement, and growth must be properly remediated. A dehumidifier can help control humidity afterwards, but it cannot repair the damage itself. That gives you a better chance of starting your next camping holiday by packing your bags, rather than arranging a damp survey.