A shipping container is a steel box built to stand outdoors: a standard 20ft unit is 6.06 × 2.44 × 2.59 m and weighs about 2.2 t empty, a 40ft about 3.8-4.0 t (see our shipping container dimensions and sizes guide). Its weak points are the three places water gets in or sits, the roof, the door seals and the floor, so maintenance is mostly a matter of checking those at each change of season.
Used containers are sold by condition grade: wind and watertight, cargo-worthy, or as-is. The grade tells you where to start. An as-is unit needs its seals and floor looked at before anything is stored in it; a new one-trip unit has made a single voyage and starts with intact paint and seals.
Why Shipping Container Maintenance Matters
The roof is a single sheet of corrugated steel, about 6.06 × 2.44 m on a 20ft container and 12.19 × 2.44 m on a 40ft. It is the part owners see least and the part that fails first, because rain and leaf litter can sit on it for months where the sheet dips between the corner posts.
Routine maintenance can help:
- Preserve structural integrity
- Improve long-term durability
- Maintain security
- Support smooth door operation
- Protect stored contents
- Reduce the likelihood of costly repairs
Perform Regular Visual Inspections
Inspect your container periodically and look for:
- Surface rust
- Dents
- Scratches
- Water accumulation
- Door alignment issues
- Seal condition
Catching problems early lets you fix them before they get worse.
Containers in harsher environments may need more frequent inspections.
Monitor for Rust
Small areas of surface rust can occasionally develop over time due to exposure to moisture and environmental conditions.
When inspecting for rust:
- Check corners and edges
- Examine roof areas
- Inspect around door frames
- Look for scratches that expose bare metal
Treating minor rust promptly stops it from spreading, since left unattended it can eventually perforate the steel.
Keep the Roof Clear
The roof carries the weather. On a 20ft container it is about 6.06 m long, on a 40ft about 12.19 m, and any low spot in that length holds water after rain; standing water and wet debris are where roof rust usually starts.
The roof is 2.44 m wide and sits between the corner posts, so leaves and branches that blow onto it tend to stay; clear it after strong winds and at each seasonal check, before the next rain.
Clearing debris from the roof regularly helps:
- Prevent water pooling
- Reduce moisture retention
- Improve overall drainage
Safe access procedures should always be followed when inspecting elevated surfaces.
Ensure Proper Drainage Around the Container
Standing water may contribute to long-term maintenance concerns and can affect site accessibility.
Our guide on preparing your property for shipping container delivery covers site preparation in more detail.
To improve drainage:
- Position containers on stable surfaces
- Avoid low-lying areas
- Keep drainage paths clear
- Monitor water flow after rainfall
Inspect Door Operation
The door opening on a standard container is about 2.34 m wide by 2.28 m high (2.58 m on a high cube), closed by two leaves on four hinges each and sealed with rubber gaskets. The doors are the only moving parts on the box, so they take most of the wear.
During inspections, check that:
- Doors open and close properly
- Hinges move freely
- Locking mechanisms function correctly
- Seals remain intact
If a door becomes difficult to operate, early maintenance may help prevent further issues.
Reliable door function is particularly important for containers used regularly for storage and business operations.
Check Door Seals
Door seals help reduce the entry of dust, moisture, and external elements.
Inspect seals periodically for:
- Cracks
- Damage
- Excessive wear
- Gaps
Each door leaf carries a rubber gasket around its full height, about 2.28 m on a standard container and 2.58 m on a high cube; a gap of a few millimetres anywhere along it lets driven rain and dust in, so the gasket is checked along its whole length, not just at the corners.
Maintain a Clean Interior
Dust, dirt and debris build up inside a container over time. Clearing them out removes:
- Dust
- Dirt
- Debris
- Moisture accumulation
A clean environment is especially beneficial when storing inventory, equipment, tools, or household items.
Routine cleaning also makes inspections easier, because you can spot problems more quickly in a clean container.
Avoid Overloading
A 20ft container weighs about 2.2 t empty and a 40ft about 3.8-4.0 t; the steel frame carries far more than any storage load, but the timber floor does not, so spread heavy items across the floor rather than stacking them in one bay.
When storing equipment or materials:
- Spread weight evenly
- Avoid excessive concentration in one area
- Follow safe loading practices
- Consider floor condition
Spreading the load evenly reduces strain on the floor in any one spot.
Maintain Adequate Ventilation
A closed 20ft container holds about 33 m³ of air and a 40ft about 67 m³. When the steel cools overnight the moisture in that air condenses on the walls and roof unless it can move, which is why stored goods sweat in an unvented box.
A vent at each end lets that air move, and keeping goods on pallets lifts them off the 5.90 m floor where condensation collects first.
Consider:
- Keeping ventilation openings unobstructed
- Monitoring humidity levels
- Periodically airing out the container if appropriate
Keeping vents clear reduces the risk of stored goods sweating in condensation.
Protect the Surrounding Area
Keep vegetation under control and remove any materials that could interfere with access or drainage.
Keeping the surrounding area clear supports:
- Improve accessibility
- Reduce moisture retention
- Simplify inspections
- Support overall functionality
Seasonal Maintenance Considerations
Australia’s weather runs from tropical wet seasons in the north to frost in the south, so a check at each change of season, four times a year, is a practical rhythm.
After periods of heavy rain, strong winds, or extreme temperatures, it can be helpful to:
- Inspect the roof
- Check drainage conditions
- Examine doors and seals
- Remove accumulated debris
Common Maintenance Mistakes to Avoid
Common mistakes include:
Ignoring Small Issues
Minor concerns can become more significant if left unaddressed.
Poor Site Preparation
Unstable ground and inadequate drainage can contribute to long-term problems.
Infrequent Inspections
Regular inspections help identify issues before they affect functionality.
Blocked Drainage
Allowing water to accumulate around the container may increase maintenance requirements over time.
Benefits of Regular Maintenance
Consistent maintenance offers several advantages:
- Improved durability
- Better security
- Enhanced functionality
- Longer service life
- Protection of stored items
- Greater overall reliability
Maintaining Your Shipping Container with BWContainers
BWContainers sells new one-trip and used containers in 10ft, 20ft, 40ft and 45ft sizes, delivered Australia-wide for a flat $200 in about 7-10 business days (see our shipping container prices page for current rates). Every unit is sold outright, so the maintenance described here is the owner’s, and it is not onerous: a walk around the box with the list above, four times a year.
By conducting routine inspections, maintaining proper drainage, monitoring for rust, and keeping your container clean, you can help protect your investment and enjoy reliable storage for many years to come.
With that care a 6.06 m or 12.19 m steel box keeps its contents dry year after year. The checks above are a walk around the container every 3 months and need no specialist.
Common questions
How do I stop rust on a shipping container?
Treat it early. Surface rust is normal on used containers and is not structural, but left alone it spreads and eventually perforates. Wire-brush the affected area back to sound metal, then prime and paint it. Inspect the roof and the underside of the door sills regularly, as those are where rust starts unnoticed.
Why is my shipping container wet inside?
Almost always condensation rather than a leak. Warm humid air enters during the day and moisture condenses on the steel as the container cools overnight, sometimes called container rain. Ventilation, insulation and desiccants all help; check the roof and door seals to rule out an actual leak first.
How often should a shipping container be inspected?
A visual check every few months is enough for most static containers, plus a look after severe weather. Check the roof for pooled water and debris, the door seals and hinges, the floor for damp, and the exterior for new rust. Problems found early are cheap to fix.
Should water be allowed to pool on a container roof?
No. Container roofs are not designed as long-term water-holding surfaces, and pooled water combined with leaf litter is the fastest route to roof rust. Keep the roof clear, and where possible site the container with a slight fall so water runs off.
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