If you’ve owned a motorhome or caravan long enough, you’ve probably felt the dread of spotting a tell-tale water stain, soft spot, or musty smell.
Water ingress is the silent enemy of RVs: slow, sneaky, and expensive if ignored. Few people know this better than Andrew Tapp, founder of RVInspections and former co-owner of Platinum Motorhomes, who has spent decades diagnosing and rebuilding vehicles suffering from leaks.
“It’s never just a damp patch,” Andrew says. “By the time you notice water, it’s usually travelled further than you think and there’ll be a much bigger story hiding behind the walls of your RV.”
Water ingress is one of the costliest problems in RV ownership and one of the most misunderstood. Andrew takes us through what it really takes to repair a leaking motorhome or caravan – from first detection to full structural rebuild – and provides advice on how you can prevent the nightmare in the first place.
Spotting the First Signs: How Leaks Reveal Themselves
Leaks rarely reveal themselves where they start. Common early clues to look out for are:
- Soft or spongy spots under vinyl or carpet floors
- Stains or bubbling in wall or ceiling linings
- Musty smells in cabinets or under beds
- Delamination – where wall panels start to bow or bubble
- Unexplained mould behind curtains or in lockers
Andrew warns that water loves to run along timbers, wiring and joints literally travelling metres inside a vehicle before emerging.
“A drip at the rear might have started near the roof cap,” he says. “Don’t assume the visible spot is the entry point.”
Playing Detective: Finding the Real Entry Point
Before any repair, the real challenge is diagnosing where water entered. Andrew draws on decades of experience when investigating, taking into consideration not just the condition of the motorhome itself but equally the surroundings – e.g. where and how is the RV parked, the angle it’s stored at, and the surface it’s parked on.
A careful visual inspection should include roof joins, windows, hatches, corner mouldings, awning rails, roof racks. In addition to this, Andrew uses a German made moisture metre to detect dampness in walls, floors and framing – arguably the best on the market as it penetrates 40mm into the wall structure. This allows you to pick up framing and insulation issues, which other moisture meters do not.
“Replacing a panel without fixing the entry point is wasted effort,” Andrew says. “You’ll have the same issue again next winter.”
Getting to the Damage: Now the Real Work Begins
Once the source of the leak is identified and the vehicle is in the workshop, the next step is to strip back affected areas. In severe cases, roof skins or side panels must come off. “It’s not for the faint-hearted,” Andrew says. “Modern RVs are lightweight but complex; you can’t just hack and hope.”
As part of this process, you need to:
- Remove furniture, cabinets, beds, and linings to access walls and floors
- Peel back vinyl, carpet or laminate to reveal timber substrates
- Disconnect electrics and plumbing where necessary
- Carefully catalogue screws and fittings for reassembly. Andrew advises photographing each stage as you go, it’ll save you hours of confusion during reassembly
How Bad Is it? Assessing the Structural Damage
Motorhomes and caravans often use timber framing with lightweight ply or composite skins. Water can rot studs, roof spars, floor joists, and ply sheets. Andrew checks:
- Extent of rot – probing with an awl or screwdriver
- Insulation condition – wet insulation must be removed
- Metal corrosion around fasteners or in aluminium-framed models
- Delamination – where glue bonds have failed
Sometimes a small visible patch hides widespread damage. “We’ve had jobs where half the floor was like a sponge cake by the time we got in there and we see plenty of black mould,” Andrew says.
“A couple of years ago, we repaired a caravan where we found that the window didn’t touch the window rubber properly. You can’t see this without knowing where to look. In the end it caused approximately $10,000 worth of damage to the front of the caravan, which was not covered by the owner’s insurance as it was deemed a manufacturing fault.”
Let the Rebuild Begin
Once damaged material is out, the rebuild begins. Make sure you dry out your RV thoroughly using heaters, dehumidifiers, and airflow. Moisture must be gone before new timber goes in.
You’ll need to replace rotted framing with treated or sealed timber, mirroring original structure for strength. Owners often assume that framing is sealed with resin but unfortunately in almost all RVs, that is not the case.
New insulation is then put in (closed-cell foam or modern non-absorbent batts). Andrew has seen quite a few imported caravans and motorhomes where polystyrene is used as insulation. It’s a cheap product and Andrew points out that it is not closed cell and if water gets in, the polystyrene soaks up and holds the water.
To illustrate, Andrew shares an eye-opening story from a few years back. He was asked to find out why a client’s pop-top kept blowing the 40 Amp relays on the lifting mechanism. The factory weight of the top was 80kg, which the relays should have easily been able to lift. Upon further investigation, it was discovered that the polystyrene core was completely sodden with water and now weighed in at a staggering 240kg!
Make sure to re-seal all joins with high-quality RV sealants (MS-based sealant) – not household silicone.
If the roof or outer walls were removed, everything must be re-bonded and mechanically fastened to manufacturer spec. “A watertight rebuild is only as strong as its prep,” Andrew says. “Shortcuts here lead to future leaks and lost resale value.”
Reinstalling Interiors – Getting It Better Than Before
Once the shell is sealed it’s time to refit cabinets, beds, and partitions, checking for square and level (movement during repairs can misalign furniture). After this you need to reconnect plumbing and wiring, ensuring no cables or pipes were damaged or pinched, and replace or reinstall floor coverings, wall linings, and trim. Before sealing everything up, make sure you test appliances such as heaters, fridges, and lights.
Andrew often improves on the original build – upgrading insulation, rerouting cables, or adding access panels for future maintenance.
Final Sealing and Testing
No job is complete without a water ingress test. Hose down joints, hatches, windows while inspecting inside. Then check that roof accessories (antennas, racks) and edge mouldings are properly bonded.
How to Avoid Repeat Disasters
Andrew’s advice for avoiding repeat disasters:
- Annual roof and seal inspection – catch cracks early
- Keep the van under cover when stored long term
- Avoid aftermarket screw holes (awnings, racks) unless properly sealed
- Check window rubbers and corner mouldings each autumn (after six months of being in the sun and out on the road over summer)
- After heavy rain, inspect interior corners for damp.
“Prevention is far cheaper than structural rebuilds,” Andrew says. “A $400 reseal every few years beats a $20,000 rot repair.”
A Reality Check – How Much It’ll Cost to Fix
“People are shocked when a ‘small leak’ becomes a structural rebuild. But once timber is compromised, you can’t ignore it,” Andrew says.
A serious leak repair is labour intensive whereas a minor reseal only takes a few hours and a few hundred dollars. A full wall/floor rebuild could mean weeks of work and can cost $10k–$25k+ depending on complexity.
When to Call an Expert
Handy owners can handle simple seal checks, but large jobs need experience:
- Structural integrity – floors and walls must be safe
- Correct materials – wrong sealants or untreated timber will fail
- Insurance and resale value – proper documentation protects value
RV Inspections offers pre-purchase checks, water ingress tests and motorhome health checks to catch water damage early. “We save people from buying a nightmare,” Andrew says.
Fixing a leaking motorhome isn’t just about slapping on more sealant (which is the most common DIY “fix” Andrew sees). It’s real detective work followed by skilled carpentry and meticulous sealing. With decades of hands-on experience at Platinum Motorhomes and now RV Inspections, Andrew knows the difference between a cosmetic fix and a safe, watertight rebuild.
“Every leak tells a story,” he says. “The sooner you listen, the better the ending – and the longer your RV adventure lasts.”
