Common in uninsulated containers — especially in autumn and winter. Here's what causes it and how to fix it.
Condensation in shipping containers occurs when warm moist air meets the cold metal walls — water vapour turns to liquid and drips onto your goods. It's common in uninsulated containers, especially in autumn and winter. The solution is ventilation, insulation, or desiccant — or a combination of all three.
Steel has high thermal conductivity — it heats and cools quickly with the outside temperature. When the external temperature drops, the container walls cool rapidly. Moisture-laden air inside the container then hits those cold surfaces and condenses into water droplets.
In the trade, this is known as 'container rain' — water literally drips from the ceiling onto goods below. It's especially pronounced in the UK's autumn and winter, when daily temperature swings are large and humidity is high.
Common triggers that make it worse: goods stored inside that have high moisture content (timber, paper, textiles), inadequate or no ventilation, and containers that are tightly sealed without airflow.
It depends heavily on what you're storing:
High risk: electronics, paper, documents, food, textiles
Moisture can destroy these goods quickly. Mould forms within days if condensation is sustained. Electronics can fail from a single damp episode.
Medium risk: tools, machinery, timber, furniture
Surface rust on metal tools, mould on untreated timber, swelling and warping in furniture. Damage accumulates over months rather than days.
Lower risk: structural steel, aggregate, tyres
Minimal short-term damage. Surface rust on steel is cosmetic unless sustained over years.
| Solution | Best for | Approximate cost |
|---|---|---|
| Ventilation (louvre vents) | Light storage, tools, plant equipment | £50–£200 fitted |
| Desiccant bags (silica gel) | Electronics, documents, seasonal storage | £5–£30 per bag, replace regularly |
| Spray foam insulation | Long-term storage, conversions | £500–£2,000 depending on size |
| Rigid board insulation (PIR) | Conversions — offices, classrooms | Part of Phil's conversion fit-out |
| Timber lining | Creates air gap, reduces condensation transfer | £300–£1,000 |
Phil can advise on the best solution for your container and use case. Call 020 8226 0007.
Yes — for conversions especially. A fully insulated container with a vapour barrier eliminates the temperature differential that causes condensation. The insulation prevents the metal walls from cooling rapidly, so moisture-laden air never reaches dew point at the surface.
For converted containers used as offices, classrooms, or welfare units, insulation is always part of the fit-out. See the container insulation service for what Phil offers.
Containers have hardwood timber floors fitted as standard. Ground moisture can rise through gaps in the container sill — particularly if the container is sited directly on soil or grass without a gap underneath.
The best practice is to sit the container on a raised hardstanding (concrete or compacted hardcore) or on timber or concrete bearers at the four corners. This creates an air gap underneath, lets any ground moisture disperse, and avoids the container floor sitting in contact with wet ground over winter. Phil's driver will flag any concerns about ground conditions on delivery.