Meter matters

QCan you still damp test a modern caravan or coachbuilt motorhome? Do you need to?

AThesimple answer is ‘yes’, but the detail is more complex than it used to be. On vehicles built using traditional methods, featuring wood framing, floors and interior wall lining, it was relatively straightforward to test for damp, often using an ‘invasive’ moisture meter (the type with two pins).

Good quality meters like that, when used with some skill, give really accurate readings and identify localised problems. There are plenty of leisure vehicles still around built in these ways and they’re particularly vulnerable should water ingress occur.

They definitely benefit from regular, thorough testing. Excess moisture can eventually cause structural failure and be hugely expensive to fix. Sadly, it can sometimes be uneconomic to do so – but catch it early and repair should be viable.

Modern Construction

Many manufacturers have replaced wood with other materials in part or throughout body structures, or have used improved construction methods and sealant materials – so techniques used to carry out tests have changed.

A really good understanding of construction methods used by specific manufacturers is needed to know where detailed testing is and isn’t required. It’s likely that testing will involve a non-invasive moisture meter (that uses radio frequency signals to penetrate through surfaces like fibreglass wall cladding), but visual inspection may be possible instead/as well.

Non-invasive meters are widely used on traditional construction models now too –avoiding the pinhole damage that sharp probes otherwise cause – although if excess moisture is found, invasive testing will give a more accurate final assessment.

Wood-free body construction is less vulnerable if water ingress does occur, but penetrating water can still cause issues –perhaps to remaining areas of wooden construction (eg some floors still include wood even if the upper body does not), or to metal parts which may corrode or glued parts which may delaminate.

Hence, most manufacturers require damp inspection during the warranty period of the vehicle and it’s vital that this is done to their specific requirements to avoid problems should a claim be necessary.

Manufacturers’ authorised service agents should have specific guidance on what’s required for individual models, as do Approved Workshop Scheme members (approvedworkshops.co.uk). If your servicing’s done by someone else, particularly on vehicles less than 10-15 years old, make sure they know the appropriate requirements and techniques.

Remain Vigilant

As an owner, it’s worth keeping an eye on vulnerable areas (eg around windows and in upper and lower corner lockers) for signs of unexpected damp. If the interior is plywood or fibreboard-lined, check for signs of staining, pimpling (raised dots indicating fungus growth) and sponginess.

Should you buy your own moisture meter? Maybe – cheap invasive and non-invasive types are around £30. They’re not as reliable as professional meters but, used regularly, they might give early warning of a change in moisture levels which can then be investigated further at a workshop. Always follow usage instructions and note that natural (eg wood) materials inherently contain some moisture. Up to 15% is no concern. Above that to 20% needs keeping an eye on –recheck in three months. Between 20% and 30% indicates a problem, while over 30% is a really serious concern.

Please address your questions to:

Technical Information, Email: technical@camc.com

Tel: 01342 336611

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