How to check a caravan or motorhome for damp

Damp means water getting into the body of your caravan or motorhome, usually past a seal or a join. It isn't the same as condensation, which forms when warm, moist air meets a cold surface such as a window or an outside wall. The NCC's guide “Condensation in touring caravans, motorcaravans and campervans” says some condensation on colder surfaces is normal, and that ventilation is the answer to it. Damp is different: it needs finding, and the way in needs fixing.

This guide covers the signs, where to look, how your construction changes the check, what meter readings mean and what your warranty asks of you. There are free printable damp report forms just below, and a printable checklist at the end.

Buying? Ask the seller for a recent damp report.

Signs you can spot without a meter

Practical Motorhome suggests these checks, and they apply to caravans too:

• A musty smell on cushions, curtains and soft furnishings.
• Staining or discolouration on the walls: black spots or marks, or a blue or pinkish tint, often near windows and lockers.
• Wall boards that feel wet, soft or spongy, or show pimpling, when you run your hands over them.
• A floor that feels spongy or creaks.
• Rust on the internal screws and fixings.

Where damp usually starts

Usually at a gap in the outside of the body. Practical Caravan lists the weak spots:

• Seals round windows, doors and rooflights, which degrade over time.
• Joins where wall panels meet.
• Anything fitted through the wall: grab handles, external sockets, lockers and cable entry points. On a motorhome, add anything drilled into the body, such as aerial points or a bike rack.
• Rooflights and roof vents.
• The front panel, which takes the brunt of the water when you're towing in bad weather.
• Wheel arches, a common source of damp.

Pressure-washing can make it worse. A technician quoted in Practical Caravan's moisture meter guide says a high-pressure washer can force water into tiny gaps.

How your construction changes the check

Timber frame with an aluminium skin

Traditional bodies were fixed together with hundreds of screws along each panel join and the awning rail, and once water gets in, the timber framework soaks it up and stays damp (source: Practical Caravan). As quoted in Practical Motorhome, older motorhomes and caravans are more likely to suffer from severe damp, especially models with wooden frames. On these, check every seam, fixing and corner.

Bonded and timber-free bodies

Newer bodies are built differently. Swift's SMART construction, for example, uses a timberless frame made from PURe, a hard polyurethane, with GRP (glass reinforced plastic) outer and inner skins. Swift's caravan floor has a GRP underside, 35mm Ravatherm insulation and an inner layer of 9mm marine-grade plywood. Bailey (Alu-Tech) and the Elddis group describe their own construction too; their warranty terms are below.

Why bonded bodies still need the floor checked

Bonded and timber-free bodies are designed to resist water, but most still use layered floors. Any layered floor can separate over time. Spongy spots near the door, kitchen or washroom are worth having a technician look at, whatever the construction.

The Approved Workshop Scheme says damp testing requirements may vary with newer construction methods and materials, and that the underside isn't tested in a routine damp check, only looked at, with anything of concern reported.

Damp meter readings: what the numbers mean

A damp meter gives a percentage. The Approved Workshop Scheme's sample damp report uses these bands:

Sources: the AWS sample damp report, and the same bands from a technician in Practical Caravan's meter guide. The bands vary slightly between reports, so read yours against the bands printed on it.

• Readings are relative. The AWS report says to compare a reading with your average readings, and notes that readings may be subject to atmospheric conditions, so the weather on the day matters.
• Simple DIY meters can be misleading. The Camping and Caravanning Club says damp checking needs good-quality equipment and expert analysis.

Bradley would suggest not using a damp meter on someone else's caravan or motorhome without asking first.

Soft or spongy floor: what it can mean

A soft or spongy floor can mean the layers of the floor are separating. The Camping and Caravanning Club lists a spongy floor among the jobs to leave to an expert, so have a technician look at it rather than trying a repair yourself.

Your annual damp report and warranty

The Approved Workshop Scheme recommends an annual service even if you only use your caravan or motorhome a couple of times a year. The damp check is part of it. Habitation checks aren't a legal requirement in the UK, but the Approved Workshop Scheme notes that many manufacturers and insurers require one every year to keep a warranty or cover valid. These body warranties are examples:

• Swift (2026 caravan owner's handbook): a 10-year extended body shell warranty for the first owner, which isn't transferable, and a 6-year body shell warranty that can pass to a new owner if the caravan has been serviced as the handbook requires.
• Bailey Alu-Tech caravans (Bailey touring caravan warranty cover): a 6-year bodyshell integrity warranty, with a paid extension to 10 years. It can pass to a new owner with Bailey's consent and a £50 transfer fee paid to Bailey, within 3 months of them taking ownership, with evidence of annual servicing. Water getting in through seams and joints that aren't permanently sealed (around windows, hatches, doors and rooflights) isn't covered after the first 36 months. These are the caravan terms; motorhome terms aren't covered here.
• The Elddis group (Elddis, Compass, Xplore and Buccaneer; source: the group's warranty page): a 10-year water ingress and body integrity warranty covering water getting in through permanently sealed joints, as long as the annual service and damp check are done by an approved retailer or service centre. Keep the invoices and damp reports as proof.

Always check your own warranty document; terms change by model year.

Selling? Why a recent damp report can help

A dated damp report and a full service history can help a buyer trust what they're looking at. If a buyer quotes readings of their own, ask where they were taken and with what meter, and offer an independent damp report instead. The guide to scams when selling a caravan or motorhome covers what to do when a buyer quotes damp readings.

Found damp? The guide to selling a caravan or motorhome with damp sets out your options, including selling it through Hitchbay while it stays with you: see selling your motorhome or selling your caravan. Selling a caravan? Have the CRiS number to hand too.

Damp findings affect what yours is worth. Here's what goes into a caravan valuation or a motorhome valuation.Get my free valuation

Free printable damp report and checklist

Work round in this order, pressing gently and taking a reading at each point. Write the reading, the date and any notes as you go, and repeat on a dry day to compare.

Motorhomes, also check:

Readings vary with the weather and between meters, and only show where to look. Get a technician to confirm anything that worries you. The reading bands are in the table above, from the AWS sample damp report.

Each form is one sheet with blank drawings of every side, the roof and the floor, so you can write each reading where you took it, plus a page on how to take readings and how often. It's your own record, filled in by you, not a professional damp report. No email needed.