How to stop damp in a caravan or motorhome

Condensation versus leaks

Condensation shows as water on windows, roof lights and cold walls, especially in the morning, and in lockers against outside walls. Leaks show as soft, stained or spongy wall boards, often near windows, roof lights, corner joints and fittings, and they get worse after rain rather than after a cold night.

A damp meter can help track readings in the same spots over time. Our guide to damp meter readings explains what the numbers can and cannot tell you. Many owners rely on the damp test that forms part of an annual habitation service by an approved workshop.

While you are using the van

Keep the fixed ventilation open; caravans are built with vents in the floor and roof for a reason, including safe use of gas appliances. Open a roof light while cooking or showering, use lids on pans and the cooker hood if fitted, and wipe windows dry each morning. Dry wet coats and towels in the awning or outside when you can, not inside the van.

Heating helps keep surfaces above the dew point. A small amount of steady heat usually works better than short blasts.

• Never block the fixed floor or roof vents
• Crack a roof light when cooking and showering
• Wipe windows and roof lights dry each morning
• Dry wet clothes outside the van
• Leave locker doors ajar so air can move

Note:Never block gas safety vents, and never use unflued gas heaters inside a caravan. Follow the van's manual for heating and ventilation.

Winter storage

Clean and dry the van fully before storage. Remove bedding, clothes, towels and food. Stand mattresses and seat cushions on edge so air can circulate. Leave lockers, cupboards and the fridge door ajar. Drain the water system as the manual describes so pipes do not freeze.

Moisture traps with refill crystals absorb a little water in a closed van, and many owners use several. They help with small amounts of moisture but cannot keep up with a wet van; see our comparison of electric dehumidifiers vs moisture traps.

Using a dehumidifier

If the van is on hook-up at home or in storage, a small dehumidifier keeps it far drier than crystals alone. Desiccant models suit caravans because they keep working in the cold, when a compressor unit slows down or ices up. Look for auto restart after a power cut, a humidistat, a timer and a drain hose option so it can run unattended. Our explainer on what a desiccant dehumidifier is explains how they work.

Check the power draw against your hook-up supply and any other loads. Desiccant units commonly draw several hundred watts on full power, and site hook-ups have limited current. Set the humidistat to a sensible target and use the timer to avoid running all day when not needed.

Compare desiccant dehumidifiers →

Catching leaks early

Most caravan leaks start at seals around windows, roof lights, awning rails, corner mouldings and fixings. Inspect sealant for cracks and gaps each season, especially after winter. Push gently on wall boards near those points; softness or a sponge-like feel is a warning sign.

If you find damp in the walls, get it assessed by an approved caravan workshop quickly. Water inside the structure can spread and is far easier to repair early. Warranties on many vans depend on annual servicing, including a damp check.

A simple routine

Before each trip, air the van and check the windows and floor. During the trip, ventilate and wipe down daily. After the trip, dry everything, open the lockers and leave a dehumidifier or traps working. Once a season, check sealant and book the habitation check. That routine catches most problems before they become expensive.

Frequently asked questions

Is a desiccant or compressor dehumidifier better for a caravan? Desiccant, in most cases, because it keeps working in a cold van and does not ice up. A compressor model suits a van kept warm.

Do moisture traps work in a caravan? They absorb small amounts of moisture in a closed van but cannot handle the amount from people living in it. They are best for storage.

How do I know if my caravan has damp? Soft or stained wall boards near windows and seals, a musty smell, and high readings on a damp meter. A workshop damp test confirms it.