In our regular Maintenance Matters column, industry expert Andrew Tapp (RV Inspections Ltd) shares practical advice and observations drawn from more than 20 years in the motorhome industry.
Over the years, I’ve seen far too many avoidable maintenance mishaps – issues that started small but ended in major, costly repairs. What surprises many owners is that the damage often wasn’t caused by neglect. It was caused by good intentions. Someone tried to fix a minor problem quickly or cheaply, using the wrong product for the job.
As a qualified RV inspector and owner of RV Inspections NZ, I inspect motorhomes and caravans of all makes and models. Using professional moisture meters, thermal imaging cameras and decades of hands-on experience, I’ve started to see clear patterns emerge. Some of the most expensive repairs I uncover can be traced back to a ‘she’ll be right’ fix that wasn’t quite right at all.
Let’s look at some of the most common quick fixes that go wrong and what should be done instead.
The Eterna Tape Trap
One of the most common red flags I see during inspections is Eterna tape on a roof.
Eterna tape is widely marketed as a permanent roof repair solution. It’s easy to apply, bonds aggressively and promises to seal leaks instantly. For many owners, it feels like the perfect answer: find a suspect joint, apply the tape, and move on.
The problem is that Eterna tape should only ever be treated as a temporary emergency fix – not a long-term repair strategy.
Recently, I inspected several RVs with tape applied across roof joins, around vents and along seams. The moment I see that tape I immediately suspect water ingress. Not because tape always fails – but because it hides what’s going on underneath.
When I conduct a full inspection using thermal imaging and moisture detection equipment, I often find significant internal water damage beneath those taped areas. In some cases, water had already entered before the tape was applied. In others, it was still tracking in around the edges.
Once tape is down, you can’t monitor the seal beneath. You can’t see whether the joint is deteriorating. You can’t confirm whether moisture is still entering. And when removal is required, it can damage roof membranes or fibreglass surfaces.
What looks like a tidy fix from the outside has, in some cases, concealed thousands of dollars’ worth of structural damage – rotted timber framing, saturated insulation and compromised interior panels.
In New Zealand’s harsh climate with strong UV exposure, wide temperature swings and sustained rainfall – roof joints are under constant stress. Tape simply isn’t designed to be your permanent waterproofing system.
The Right Approach
If you suspect a leak:
- Use tape only as a temporary emergency measure
- Identify the true source of water entry
- Remove old, failing sealant completely
- Reseal properly using an MS-based (Modified Silane) sealant
- A proper repair allows the joint to be monitored, maintained and re-serviced over time rather than hidden and forgotten.
Silicone: Inside Yes, Outside No
Silicone is another product that causes significant long-term headaches, particularly when used externally.
Let me be clear: silicone absolutely has a place inside your motorhome. It performs well around internal wet areas such as kitchens, bathrooms, basins and shower trays. In these locations, it provides flexibility and water resistance where movement is minimal and exposure is controlled.
But silicone should not be used on the exterior of your RV.
Why Silicone Fails Outside
Externally, silicone has several serious drawbacks:
- It doesn’t adhere well to many RV construction materials long-term
- It stains surrounding surfaces
- It cannot be painted
- Nothing bonds to cured silicone – not even fresh sealant
- It is extremely difficult to remove without damaging panels
From a repairer’s perspective, exterior silicone is one of the most frustrating products to deal with. When it fails – and eventually it will – the removal process is labour intensive and messy. Any residue left behind prevents proper adhesion of new sealant or paint, making future repairs more complex and expensive.
What to Use Instead
For exterior fittings, roof seams, windows and body joints, an MS-based sealant is far superior.
MS-based sealants:
- Adhere to aluminium, fibreglass and composite panels
- Remain flexible under movement
- Offer strong UV resistance
- Can be painted
- Are serviceable and repairable
- Your motorhome flexes constantly while driving. Exterior sealants must be designed for that movement. Silicone simply isn’t.
Expanding Foam Fails
Expanding foam might seem like a clever way to block drafts or seal gaps, especially for winter insulation. Unfortunately, it often creates bigger problems than it solves.
I’ve seen expanding foam sprayed into wall cavities, around wiring and into structural voids. The intention is usually to ‘seal’ a leak or improve insulation. But foam expands aggressively and unpredictably.
What goes wrong:
- It can engulf electrical wiring
- It traps moisture inside wall cavities
- It makes future access almost impossible
- It can distort or bulge panels
In colder regions of New Zealand, I’ve seen foam intended as insulation actually increase condensation issues. Moisture becomes trapped, unable to escape or dry properly. Insulation and sealing should be deliberate and ventilated – not sprayed blindly into cavities.
The ‘Hardware Store Sealant’ Mistake
Not all sealants are created equal. RVs travel thousands of kilometres across winding highways and corrugated rural roads. The constant torsional stress means your caravan or motorhome flexes every time you drive. Generic construction adhesives or roofing sealants, commonly bought from hardware stores, are often too rigid for RV use.
What goes wrong:
- Rigid products crack under movement
- Adhesion fails prematurely
- Water enters behind brittle joints
- A product suitable for house roofing may not survive a South Island road trip. I recommend always using products specifically rated for RV movement.
Painting Over Problems
One of the simplest, and most dangerous, shortcuts I see is painting over interior water stains. Owners notice a discoloured patch on a wall lining and apply a fresh coat of paint. It looks tidy. Problem solved – or so it seems. In reality, the moisture source remains, structural rot may continue behind the wall and insurance claims become complicated later.
This is particularly common in older imported caravans that weren’t designed for New Zealand’s heavy rainfall.
Paint hides symptoms. It doesn’t cure causes.
Using the Wrong Products to Clean Your Roof
Keeping the roof of your motorhome clean is important – but using the wrong tools can cause damage. Water blasters are extremely popular in New Zealand. Unfortunately, they can be disastrous on RV roofs.
High-pressure water can force moisture under seals, damage membrane roofs and strip protective coatings. I’ve seen perfectly good roof seals compromised by aggressive cleaning. Instead, I recommend using low-pressure washing, soft brushes and products designed specifically for RV roofing materials.
Cheap Replacement Fittings
With New Zealand’s high UV levels, plastic components degrade faster than many owners realise. Replacing a cracked hatch or vent with a cheap aftermarket product may save money initially – but low-grade plastics often warp or fade within a year.
What goes wrong:
- Poor UV resistance
- Warping and seal distortion
- Incompatible seals leading to leaks
- Investing in quality replacement parts is far cheaper than repairing water damage caused by inferior fittings.
Blocking Designed Drainage Paths
Another common DIY error is sealing over window weep holes because they ‘look like leaks’. Weep holes exist to allow water to drain safely from window frames. Blocking them traps water instead. The result? Moisture accumulates, timber framing begins to rot and internal damage develops quietly.
If you see a small hole, don’t assume it’s a fault. It may be there by design. If you’re unsure, get an expert to look at it for you.
The ‘She’ll Be Right’ Electrical Patch-Up
Electrical shortcuts are particularly concerning. Twisting wires together or using household connectors in damp compartments can lead to corrosion, overheating and even fire risk. New Zealand’s electrical compliance requirements – including WoF and CoF obligations – are strict for good reason.
Electrical repairs should always be completed using proper marine or RV-rated connectors and moisture protection methods.
Foam Gaskets: A Growing Problem
Increasingly, I’m seeing caravans constructed with foam gaskets around windows and habitation doors instead of bonded sealant systems. On paper, foam gaskets appear neat and efficient. In practice, they’re causing widespread water ingress issues.
Foam gaskets rely solely on compression. They do not bond the window or door frame to the body shell.
Because these gaskets are typically black or grey, they absorb heat and shrink over time. In New Zealand’s climate, with strong sun followed by heavy rain, that shrinkage creates gaps.
The issue worsens in caravans with corrugated side panels. Foam compresses unevenly along ridges, leaving micro-gaps where water can track in – especially while towing in heavy rain.
I’ve inspected numerous caravans where owners were shocked to learn that windows appearing perfectly sealed externally were leaking internally.
Windows and doors should be sealed using MS-based sealants that bond the fitting securely to the body shell. Compression-only systems simply aren’t robust enough for New Zealand conditions.
A bonded seal:
- Prevents water tracking
- Handles structural movement
- Maintains integrity under towing stress
- Provides long-term protection
Water Ingress: The Silent Destroyer
Water ingress is the most expensive issue I uncover during inspections. Water doesn’t sit still. It travels along framing, insulation and linings. By the time visible damage appears, structural issues may already be extensive.
Thermal imaging reveals hidden moisture patterns long before they’re visible. Moisture meters quantify the problem. I use both in my inspections.
Time and again, what appears minor turns out to be structural. And more often than not, it began with a shortcut.
Common DIY Mistakes to Avoid
Beyond the major issues above, I frequently see problems in RVs caused by:
- Using household products externally – not UV resistant or flexible enough
- Mixing incompatible sealants – leading to bonding failure
- Ignoring surface preparation – even good sealant fails on dirty surfaces
- Over-sealing joints – trapping moisture rather than preventing it
- Doing the job properly means removing old material, preparing surfaces and using compatible products.
Prevention Is Always Cheaper
Annual moisture inspections, careful product selection and regular visual checks of roof fittings and seals can prevent major repairs. Before using any product, ask:
- Is it designed for RV exterior use?
- Is it UV resistant?
- Can it handle movement?
- Is it compatible with my vehicle’s materials?
- If you’re unsure, seek professional advice.
The Takeaway
Maintenance mishaps rarely happen overnight. They build slowly, often hidden beneath tape, silicone or foam gaskets that were meant to solve a problem. Your motorhome or caravan is a significant investment. Using the right product in the right place protects that investment.
If in doubt, have it inspected properly or ask an expert. It’s far better to catch a minor issue early than to face major damage later.
Safe travels.
Andrew Tapp is a veteran of the motorhome and boatbuilding industries. He converted his first 9m Hino in 2002 before designing his own series of luxury motorhomes. He has worked on all classes and types of RVs, motorhomes and caravans and has seen it all. He now puts his decades of experience to good use, providing prepurchase inspections, Water Ingress Tests and RV Health Checks.
