Shipping Container Storage: An Honest Guide from a Self Storage Owner
What we have learned since moving into self storage
Written by Steve McLoughlin, Director of Alliance Self Storage
Steve has operated drive-up self storage sites on the Wirral since 2017 and has helped thousands of domestic and business customers. Alliance operates SSA UK-approved storage facilities in Moreton and Birkenhead, inspected in 2023 and 2025.
Last reviewed: July 2026
Alliance did not begin as a self storage company. We originally worked in transport and haulage, and storage gradually became part of the service we offered alongside it.
Over time, I realised that haulage was not where my real passion was. Much of the work involved dealing with large, faceless companies. Self storage was different. It brought us into contact with real people, often at important or stressful times in their lives.
Some customers are moving home. Others are dealing with a bereavement, clearing a property, renovating or trying to create more space. Many are starting a business or have reached the stage where that business is growing faster than the room available at home.
We made the full move into self storage in July 2017. Since then, one thing has remained constant: our job is to make storage as simple and stress-free as possible.
Customer service is a huge part of that, but security comes first in the background. A CCTV camera might look like just another camera to a customer. To us, it is one of the most important parts of the business. We invest heavily in monitoring, access control and new technology because customers are trusting us with belongings that may be valuable financially, emotionally or both.
We have also learned that people often keep their units for far longer than they originally expected. Once they experience the convenience of being able to drive directly to their own unit, they begin to see how useful that extra space can be.
This guide contains the advice we give our own customers every day. It is based on what we have genuinely seen work—and occasionally what we have seen go wrong—rather than information copied from other storage websites.
In this guide
In this guide
- Does shipping container storage get damp?
- What makes a good quality storage container?
- Is drive up storage better than indoor storage?
- How secure is shipping container storage?
- What should you check before booking?
- How should you pack a storage unit?
- How much storage space do you need?
- Storage for moving home
- Storage for businesses and tradespeople
- What cannot be stored?
- StoreProtect and protecting your belongings
- Frequently asked questions
Does shipping container storage get damp?
This is probably the question we are asked more than any other.
There is still a common belief that anything stored inside a shipping container will eventually become damp or mouldy. That reputation normally comes from old, damaged containers placed directly onto wet ground, with little ventilation and poor maintenance.
A modern one-trip container that is properly positioned, ventilated, inspected and used correctly is completely different. We have operated drive-up self storage since 2017 and have never seen furniture ruined by damp inside one of our storage units.
Container storage is not climate-controlled, so belongings still need to be prepared properly. However, in our experience, the condition of the container and what the customer puts inside it make the biggest difference.
What causes condensation inside a shipping container?
Condensation happens when moisture in the air meets a colder surface and turns into water droplets.
What causes condensation inside a shipping container?
Condensation happens when moisture in the air meets a colder surface and turns into water droplets.
The steel walls and roof of a shipping container can become colder than the air inside, particularly overnight. If there is too much moisture trapped inside the unit, small droplets can form on the colder metal surfaces.
That moisture does not normally appear from nowhere. It is usually brought into the container through damp belongings, wet equipment, appliances containing trapped water or a poorly maintained unit that allows water to enter.
This is why ventilation, correct positioning and making sure everything goes into storage completely dry are so important.
How Alliance reduces the risk of damp and condensation
All Alliance storage units are one-trip shipping containers. We keep them clean and well maintained, repainting them when necessary rather than allowing them to deteriorate.
Each standard unit has approximately 12 ventilation points, allowing air to move through the container rather than becoming trapped.
Our units also have 30mm bamboo flooring, treated and sealed underneath to help protect against damp and pests.
We do not simply place the containers onto wet or uneven ground. They sit on concrete pads and are raised by at least 25mm. Even this small clearance helps create airflow beneath the container and keeps the floor away from damp ground.
Our containers are raised on concrete pads to keep the floor away from damp ground and allow airflow underneath.
Every unit is inspected at least once every three months. When a customer leaves, we fully clean the container and check the doors, seals, handles, floor, vents and lock box before it is rented again. If the inside needs repainting, we do that as well.
Paperwork stored in shipping containers for over 15 years
A business based on one of our sites has stored paperwork inside shipping containers for more than 15 years.
The paperwork was originally stored inside an older container and was later moved into a new one-trip container supplied by Alliance. During the whole period we have personally known about it, the paperwork has remained dry and usable.
Paperwork is one of the belongings people are most concerned about storing, so this gives us a very good long-term example of what properly managed container storage can achieve.
We also have many customers storing sofas, mattresses and other soft furnishings without experiencing damp problems.
The most important rule: put everything into storage dry
A high-quality container cannot remove large amounts of moisture brought in on wet belongings.
The most important rule: put everything into storage dry
A high-quality container cannot remove large amounts of moisture brought in on wet belongings.
Washing machines can retain water inside the drum, filter, pump and hoses. They should be drained properly and allowed to dry before being placed into storage.
Fridges and freezers should be completely emptied, defrosted and dried.
We recommend leaving the doors slightly open while they are stored so that air can circulate inside and mould or unpleasant smells do not develop.
We recommend leaving the doors slightly open while they are stored so that air can circulate inside and mould or unpleasant smells do not develop.
Garden furniture, tents, inflatable equipment and anything used outdoors should also be completely dry. An item may feel dry on the surface while still holding moisture in folds, seams or fabric.
Covers can be used to protect sofas and mattresses from dust and accidental marks, but the furniture itself must be dry before it is covered.
Alliance’s Best Tip: If it goes in dry, it should come out dry.
In a sound, properly ventilated and correctly maintained container, belongings that enter completely dry should remain dry under normal storage conditions. Always drain appliances and dry outdoor equipment before closing the unit.
The only significant condensation we have personally seen
The only significant condensation we have personally seen inside one of our units involved bouncy castles.
The equipment was regularly used outdoors and sometimes put back into the container while still wet from damp grass. That moisture was carried into the unit with the equipment and then became trapped inside.
The container had not created the water. The water had entered with the wet bouncy castles.
This is a useful real-world example because it shows why even a well-ventilated storage container cannot compensate for large amounts of moisture being brought inside.
How to prevent damp in a storage container
- Choose a clean, sound and properly ventilated unit.
- Check that the container is raised off the ground.
- Make sure doors and seals are in good condition.
- Put only completely dry belongings into storage.
- Drain washing machines and their hoses.
- Fully defrost and dry fridges and freezers.
- Leave appliance doors slightly open.
- Dry tents, garden furniture and outdoor equipment thoroughly.
- Avoid blocking all the ventilation points.
- Report any sign of water ingress to the storage company immediately
A reputable storage company should be able to explain how its containers are ventilated, what they sit on and how frequently they are inspected. It should also be willing to show you the actual site and unit before you book.
What makes a good-quality storage container?
Not all shipping-container storage is the same.
From a distance, two storage sites can look very similar. Both may use shipping containers and both may describe their units as clean, dry and secure. The real difference is often found in the condition of the containers, how they have been positioned, how they are maintained and the security surrounding them.
A good storage company should be able to explain exactly what type of containers it uses and what it does to keep them in good condition. It should also be happy to show customers genuine photographs or videos of the actual site and units being offered.
At Alliance, all our storage units are one-trip containers. This means they have normally completed only one journey carrying goods before being converted for self storage. We chose one-trip units because they give customers a cleaner, newer and better-maintained space than old shipping containers that may have spent many years at sea.
Not all shipping-container storage is the same.
From a distance, two storage sites can look very similar. Both may use shipping containers and both may describe their units as clean, dry and secure. The real difference is often found in the condition of the containers, how they have been positioned, how they are maintained and the security surrounding them.
A good storage company should be able to explain exactly what type of containers it uses and what it does to keep them in good condition. It should also be happy to show customers genuine photographs or videos of the actual site and units being offered.
At Alliance, all our storage units are one-trip containers. This means they have normally completed only one journey carrying goods before being converted for self storage. We chose one-trip units because they give customers a cleaner, newer and better-maintained space than old shipping containers that may have spent many years at sea.
The condition of the container matters
A storage container does not remain in good condition simply because it was new when it arrived.
Doors, handles, seals, vents, floors and lock boxes all need checking. Paintwork also needs maintaining so that small areas of damage do not develop into larger problems.
We inspect every Alliance unit at least once every three months. When a customer leaves, the unit is fully cleaned and checked before it is rented again.
We inspect the doors, handles, seals, ventilation points, floor and lock box, and repaint the inside or outside where needed.
This is important because customers often store with us for much longer than they originally planned. A unit should remain clean, secure and easy to use throughout the whole storage period, not just look good on the day someone moves in.
Doors, handles, seals, vents, floors and lock boxes all need checking. Paintwork also needs maintaining so that small areas of damage do not develop into larger problems.
We inspect every Alliance unit at least once every three months. When a customer leaves, the unit is fully cleaned and checked before it is rented again.
We inspect the doors, handles, seals, ventilation points, floor and lock box, and repaint the inside or outside where needed.
This is important because customers often store with us for much longer than they originally planned. A unit should remain clean, secure and easy to use throughout the whole storage period, not just look good on the day someone moves in.
A strong, properly protected floor
The floor is one of the most important parts of a storage container, but it is something customers do not always think to check.
Our one-trip units have 30mm bamboo flooring. The underside is treated and sealed to help protect the floor against damp and pests.
The floor should feel solid, clean and level when you walk across it. Customers should be cautious of units with damaged flooring, soft areas, strong smells or signs that water has previously entered.
A strong floor is particularly important for business customers storing tools, machinery, stock or heavy shelving. The combined weight of stored items can soon add up.
Our one-trip units have 30mm bamboo flooring. The underside is treated and sealed to help protect the floor against damp and pests.
The floor should feel solid, clean and level when you walk across it. Customers should be cautious of units with damaged flooring, soft areas, strong smells or signs that water has previously entered.
A strong floor is particularly important for business customers storing tools, machinery, stock or heavy shelving. The combined weight of stored items can soon add up.
Ventilation and correct positioning
A quality storage container should have proper ventilation and should not simply be placed directly onto damp or uneven ground.
Each standard Alliance unit has approximately 12 ventilation points to help air move through the container.
Our containers sit on concrete pads and are raised at least 25mm above the ground. This keeps the floor away from damp ground and allows air to circulate underneath.
Ventilation and positioning work together. A well-maintained container can still be let down if it is badly placed, and a raised container can still develop problems if the ventilation points are blocked or damaged.
A quality storage container should have proper ventilation and should not simply be placed directly onto damp or uneven ground.
Each standard Alliance unit has approximately 12 ventilation points to help air move through the container.
Our containers sit on concrete pads and are raised at least 25mm above the ground. This keeps the floor away from damp ground and allows air to circulate underneath.
Ventilation and positioning work together. A well-maintained container can still be let down if it is badly placed, and a raised container can still develop problems if the ventilation points are blocked or damaged.
Doors should be secure and easy to open
Shipping-container doors are extremely strong, but older or poorly maintained doors can become difficult to use.
A customer should be able to open and close the unit without struggling with seized hinges, badly aligned locking bars or damaged seals.
Our containers are fitted with easy-opening handles, and the doors and locking mechanisms are checked regularly. This is particularly helpful for customers who may not have the strength or experience to operate traditional shipping-container doors.
The rubber door seals should also be in good condition. Damaged or missing seals can allow wind-driven rain and dirt to enter the unit.
A customer should be able to open and close the unit without struggling with seized hinges, badly aligned locking bars or damaged seals.
Our containers are fitted with easy-opening handles, and the doors and locking mechanisms are checked regularly. This is particularly helpful for customers who may not have the strength or experience to operate traditional shipping-container doors.
The rubber door seals should also be in good condition. Damaged or missing seals can allow wind-driven rain and dirt to enter the unit.
A proper lock box and heavy-duty padlock
The type of lock fitted to a storage unit can make a significant difference to its security.
Our units have steel lock boxes fitted around the locking point. These help shield the padlock and make it much harder to reach with cutting equipment.
Customers can use their own suitable lock or purchase one of our heavy-duty padlocks. However, we prefer customers to use the locks we supply because they fit properly inside our lock boxes.
From speaking with other self storage operators through the Self Storage Association, we have repeatedly heard that units fitted with cheap padlocks on exposed door handles are more vulnerable than units using a suitable heavy-duty lock protected inside a lock box.
We occasionally provide one of our locks free of charge because we would rather know that the unit has been secured properly than see a customer rely on a cheap or unsuitable padlock.
The type of lock fitted to a storage unit can make a significant difference to its security.
Our units have steel lock boxes fitted around the locking point. These help shield the padlock and make it much harder to reach with cutting equipment.
Customers can use their own suitable lock or purchase one of our heavy-duty padlocks. However, we prefer customers to use the locks we supply because they fit properly inside our lock boxes.
From speaking with other self storage operators through the Self Storage Association, we have repeatedly heard that units fitted with cheap padlocks on exposed door handles are more vulnerable than units using a suitable heavy-duty lock protected inside a lock box.
We occasionally provide one of our locks free of charge because we would rather know that the unit has been secured properly than see a customer rely on a cheap or unsuitable padlock.
Make sure you are looking at the actual site
Before booking outdoor storage, we recommend visiting the site or asking the company to send a current video of the actual unit being offered.
Look for genuine photographs of the containers, access roads, perimeter, entrance and security arrangements. Be cautious if a storage company relies heavily on stock photographs, computer-generated images or pictures that do not appear to show its real facility.
A good operator should be proud to show customers the site and explain how the units are maintained. If the photographs avoid showing the inside of the containers, the condition of the doors or the ground they sit on, it is reasonable to ask why.
Look for genuine photographs of the containers, access roads, perimeter, entrance and security arrangements. Be cautious if a storage company relies heavily on stock photographs, computer-generated images or pictures that do not appear to show its real facility.
A good operator should be proud to show customers the site and explain how the units are maintained. If the photographs avoid showing the inside of the containers, the condition of the doors or the ground they sit on, it is reasonable to ask why.
Alliance’s Best Tip: Do not judge a storage unit by its fresh paint alone.
Check the floor, vents, door seals, handles, lock box and what the container is sitting on. A coat of paint can make an old unit look better, but it does not correct poor ventilation, damaged flooring or badly maintained doors.
A quick quality checklist
- Is it a modern, sound container?
- Is the inside clean and free from strong smells?
- Is the floor solid, clean and undamaged?
- Are ventilation points fitted and unobstructed?
- Is the container raised away from damp ground?
- Are the doors easy to open and close?
- Are the door seals complete and in good condition?
- Is a protective steel lock box fitted?
- Is a suitable heavy-duty padlock available?
- Does the operator carry out regular inspections?
- Can you see genuine photographs or video of the actual site?
- Are you able to view the unit before booking?
A storage company should be able to answer these questions clearly. Customers are trusting the operator with belongings that may have significant financial or sentimental value, so there should be no need to hide the condition of the units or the way the site is managed.