Are Shipping Containers Waterproof?

Common Damage Points to Watch for in a Shipping Container

When inspecting a shipping container for potential leaks or structural issues, these are the areas that deserve the closest attention:

Door seals and gasket edges

Door gaskets often wear out first, developing cracks, brittleness, or uneven compression that allows wind-driven rain to seep through. Check for gaps, tears, or areas where the seal no longer tightens properly.

Corner castings

These load-bearing corners endure significant stress during lifting and stacking. Dents, cracks, or corrosion in the corner castings can open seams to water infiltration and may indicate the container has been mishandled.

Roof dents (especially in the center)

A dented roof can trap water, accelerating rust and eventually creating pinholes. Pay special attention to the center of the roof, where depressions from forklift tines or falling debris are most common.

Warped or bulging walls

Walls that bow inward or outward indicate past stress or impacts. This warping can create micro-cracks along seams and compromise the container's ability to shed water effectively.

Corroded welds

Rust around weld seams weakens the steel and can develop into small leaks. Pay extra attention to welds near the roofline and corners, where moisture tends to collect.

Impact damage from forklifts or stacking

Improper handling during forklift operations or stacking can cause hidden dents and structural stress, creating weak spots where water eventually infiltrates.

How To Test If a Shipping Container Is Watertight

Before you buy a shipping container, it's important to verify its water resistance. These simple tests help you catch leaks early and ensure the container is suitable for long-term use

Visual and DIY leak tests

1. Flashlight test (Inside): Shine a bright flashlight around the exterior seams. If light appears inside, water can too.
2. Closed-door daylight test: Step inside during the day and close the doors. Any rays of light indicate potential leak points.
3. Hose test: Spray the container roof and doors with a water hose. Look for drips inside.

How To Waterproof a Shipping Container

Waterproofing a shipping container requires a multi-layered approach that addresses potential leak points and environmental factors.

Inspect and replace door seals

Inspect the edges carefully for any gaps, tears, or uneven compression when closing the doors. If you notice damage, replace the gaskets promptly. Regularly checking and maintaining these seals is one of the simplest yet most effective ways to prevent leaks.

Seal vulnerable joints and seams

Applying roof sealants, elastomeric coatings, or waterproof exterior paint can add an extra layer of protection. Bitumen tape or specialized weather barriers can also reinforce aging or thin areas, preventing moisture from seeping through.

These steps are especially important for older or previously used containers, where wear and tear may have compromised the original seals.

Elevate and properly site the container

Proper placement significantly affects water resistance. Avoid placing your container directly on soft soil, grass, or areas with poor drainage. Instead, elevate it on concrete blocks, gravel pads, or steel beams to promote airflow beneath the container.

This elevation reduces moisture accumulation and slows corrosion on the base, making well-sited containers far less prone to floor rot, rust, and damage from pooling water. For further details on how to keep your shipping containers
secure, check out How to secure your shipping container

Install a protective roof or canopy

In regions with heavy or frequent rainfall, adding a secondary roof can dramatically extend the container’s lifespan. Prefabricated metal canopies, lean-to structures, sloped framed roofs, or even heavy-duty tarps can prevent standing water on the roof and reduce direct exposure to the elements.

How To Prevent Internal Moisture And Condensation

Moisture is a common problem in shipping containers. Steel walls transfer heat rapidly, causing temperature fluctuations that lead to "cargo sweat": condensation that forms when warm interior air cools against cold metal surfaces. This moisture can damage stored items, promote mold growth, and cause rust.

Control moisture with these methods:

• Add passive vents: Allow natural airflow without electricity, balancing temperature and reducing condensation. Best for general storage and mild climates.
• Install turbine vents: Wind-powered vents actively remove humid air through constant circulation. Ideal for hot or humid environments.
• Use spray foam insulation: Creates a thermal barrier that stabilizes temperature, prevents condensation, and strengthens the container.
• Place desiccant packs inside: Absorb excess moisture in sealed containers. Inexpensive and effective in climates with fluctuating humidity.

Proper moisture control protects your stored items over time. For additional ventilation strategies, see Top Techniques for Effective Shipping Container Ventilation or explore insulation options in our guide on choosing the right insulation type for shipping containers.

When Should You Consider Extra Waterproofing?

While shipping containers are built to be watertight, there are certain situations where adding extra waterproofing can provide peace of mind and protect your investment. Consider additional water protection if your container will be exposed to:

• Flood-prone locations: If your container is in an area that experiences frequent flooding or heavy storms, extra waterproofing can prevent water from seeping in during extreme conditions.
• Long-term outdoor storage: Containers left outdoors for extended periods are constantly exposed to rain, snow, and humidity. Reinforcing their water resistance can help extend the lifespan of a shipping container and protect the items stored inside.
• High-humidity environments: Coastal regions or tropical climates create moisture-rich conditions that accelerate rust and condensation. Additional waterproofing or protective coatings can minimize these risks.
• Container homes: When converting a container into a living space, even minor leaks or condensation can cause structural damage, mold, or discomfort. Extra sealing and weatherproofing ensure a safe, dry, and comfortable interior while extending the container home life span.

This protective layer safeguards both your container and its contents against challenging environmental conditions. It's especially valuable when repurposing shipping containers for creative new projects.

Tips for Choosing a Watertight Container

When buying a used container, look for the WWT (Wind and Watertight) certification. This guarantees that no daylight is visible through the walls or roof, doors are sealed properly, and the container has passed basic leak tests. Before buying, always:

• Ask about the container’s age, condition, and previous use
• Request a Wind & Watertight (WWT) certification
• Perform on-site inspection tests
• Never assume every container is leak-free

Containers without WWT certification may require repairs before they can reliably resist weather and prevent leaks.

Viva Containers offers high-quality containers designed to withstand the toughest environments. Offering both new and used containers, including specialized options like high cubes, open sides, and double-door models, ensuring you find the perfect fit for your project. Every container goes through a rigorous inspection and quality assurance process, so you can feel confident that you’re investing in a structurally sound and weather-resistant unit.

Take a look at our container listings online or get in touch for a personalized quote, and let Viva Containers be your reliable partner.