by Damp in a van gets ignored because it presents as a nuisance rather than a fault. It matters more than it looks: persistent moisture in the load area rots the floor from underneath the lining, corrodes anchor points, ruins stock and tools, and eventually turns into structural corrosion that fails an MOT.
First, decide which problem you have
Everything downstream depends on this distinction.
Condensation
Moisture from the air condensing on cold surfaces. Characteristics: it appears fairly evenly across cold panels, is worse in cold weather and overnight, is worse when the van has been carrying people or wet materials, and it usually clears with ventilation and warmth. Metal panels and the inside of the roof are typically the wettest points.
A leak
Water entering from outside. Characteristics: localised rather than general, worse after rain or a wash rather than after cold nights, often shows a tide mark or a trail, and may correlate with a particular panel, seal or fitting.
The quickest way to separate them: does it get worse after rain, or after a cold dry night? Rain points to a leak, cold dry nights point to condensation.
Where water actually gets into a panel van
- Door seals, particularly the sliding door and rear barn doors, which take the most use and perish first. See sliding door faults.
- Blocked drain holes in doors and sills, so water that is supposed to drain out sits inside instead.
- Roof fittings. Roof rack mountings, aerials, roof vents and any hole drilled for an accessory. A very common source, especially where sealant has aged.
- Windscreen and window seals, particularly after a screen replacement. See windscreen, wiper and washer faults.
- Bulkhead and body seams, where factory sealant has cracked with age and flex.
- Rear light clusters, where the seal against the body has perished. Often shows as water in the light unit too. See van lighting faults.
- Corroded panels, where perforation has created a hole. At this point the damp is a symptom of a bigger problem. See van corrosion.
- Blocked bulkhead or scuttle drains, which cause water to back up and enter the cab, typically appearing as a wet footwell.
- Heater matrix leak, which is coolant rather than water. Sweet smell, greasy film on the inside of the glass, and a dropping coolant level. Entirely different problem. See coolant loss with no visible leak.
Finding a leak
1. Dry everything thoroughly first
You cannot trace a leak in a van that is already wet everywhere. Get it dry, then work systematically.
2. Work from the inside with a torch
Have someone hose the van in sections, starting low and working up, while you watch from inside with a torch. Take your time on each section. Starting low matters, because water entering high runs down and appears somewhere else entirely, which is what makes leak tracing frustrating.
3. Look for tide marks and trails
Dried water leaves marks. Follow them upwards to find the entry point, remembering that the wet patch is usually below where the water actually got in.
4. Check the obvious fittings
Any hole drilled into the body for an accessory is a candidate. Roof racks, aerials, beacons and reversing cameras are frequent culprits, particularly where the sealant has aged or the fitting was not done well.
5. Lift the load floor lining
This is where the damage happens unseen. Water sits between the ply and the metal floor and corrodes it from above while everything looks fine.
6. Check the drains
Door bottoms, sills and the scuttle area below the windscreen. Clear them with a soft probe rather than anything that could damage the seal.
Dealing with condensation
Condensation is about moisture, temperature and airflow, so the fixes address those.
- Ventilate. Leave the van open when parked securely, or run the ventilation on fresh air rather than recirculation when driving.
- Do not carry wet materials unnecessarily. Wet dust sheets, damp sand and wet clothing put a lot of moisture into the air.
- Insulate if the van is used in a way that justifies it. Insulation raises the surface temperature of the panels so moisture is less likely to condense on them. Done badly, however, insulation traps moisture against the metal and accelerates corrosion, so it needs doing properly with a vapour barrier and adequate ventilation.
- Use a dehumidifier or moisture absorber in a van that stands, which is cheap and effective.
- Run the air conditioning periodically, since it dehumidifies as well as cools.
Why it matters
Beyond comfort and ruined stock, persistent damp corrodes the load floor and body from the inside, promotes mould, and can affect electrical connectors and lighting. It also devalues the van noticeably: a damp load area with a corroded floor is one of the first things a buyer or inspector looks for. See buying a used van.
Indicative UK costs
Broad context only. Clearing drains and resealing a fitting costs little beyond time and a tube of suitable sealant. Door seals are typically modest parts. Windscreen reseal or replacement runs into the hundreds. Load floor corrosion repair varies enormously with extent. A dehumidifier or moisture absorber is a few pounds. Get quotes for anything structural.
Common mistakes
- Treating a leak as condensation, or vice versa. The fixes are completely different.
- Hosing from the top down when leak tracing. Water runs and misleads you. Start low.
- Never lifting the load floor lining. Where the real damage accumulates.
- Sealing over the symptom. Smearing sealant at the wet patch rather than finding the entry point higher up.
- Insulating without a vapour barrier. Traps moisture against the metal and accelerates rust.
- Ignoring a sweet smell. That is coolant from a heater matrix, not rainwater.
When to get help
Get help if you cannot find the entry point after systematic testing, if there is corrosion in the load floor or structure, or if you suspect a heater matrix leak, which means dashboard removal on many vans. Also get help if damp is affecting electrical connectors, since that leads to intermittent faults that are hard to trace later.
Prevention
Keep drain holes clear. Inspect and replace door seals before they perish. Reseal roof fittings periodically, since sealant ages. Ventilate the van rather than leaving it sealed and damp. Avoid carrying wet materials where possible. Lift the load floor lining occasionally to check underneath, particularly on an older van.
Frequently asked questions
How do I tell condensation from a leak?
Condensation is general across cold surfaces and worse after cold nights. A leak is localised and worse after rain.
Should I insulate my van to stop condensation?
It helps if done properly with a vapour barrier and ventilation. Done badly it traps moisture against the metal and causes corrosion.
Water in the passenger footwell. Where from?
Commonly a blocked scuttle drain below the windscreen, a door seal, or a windscreen seal. If it smells sweet and is slightly greasy, it is coolant from the heater matrix instead.
Is damp in the load area serious?
It becomes serious. It corrodes the floor and anchor points from beneath the lining, and it will eventually become a structural and MOT problem.
This guide is general information for UK van owners, not vehicle-specific repair instructions. Procedures, tolerances and component layouts vary by engine code and model year. Confirm any figures against your VIN and manufacturer workshop information, and see our Disclaimer before carrying out any work.
