Used Shipping Container Inspection Checklist: What to Evaluate Before You Buy

Most shipping container purchases in the US happen sight unseen — you order online or by phone, and the container arrives on a tilt-bed trailer without you ever having set foot in the depot. That's standard practice and perfectly safe when you're buying from a graded, verified supplier. But knowing what a proper WWT-grade container should look and feel like when it arrives — and what to do if it doesn't — is the difference between a confident purchase and a dispute after delivery. This checklist covers every element worth evaluating, whether you're inspecting in person at pickup or reviewing a container on delivery day.

Understanding WWT Grade Before You Inspect

WWT (Wind and Water Tight) is the standard grade for used containers sold for storage and job site use. It's a functional certification, not a cosmetic one. A WWT container is guaranteed to:

• Be structurally sound — walls, roof, and floor hold their shape and integrity
• Have doors that open, close, and seal completely
• Show no active water ingress through the roof, walls, floor, or door seals

WWT does not guarantee:

• Absence of surface rust (expected on any used unit)
• Specific color or paint condition
• Absence of dents, dings, or cosmetic damage
• Odor-free interior (cargo history can leave residual smells)

Setting the right expectations before delivery prevents most disputes. If the container is structurally sound, watertight, and functionally operable — it meets WWT grade regardless of how it looks.

Exterior Inspection Checklist

Roof

• Walk around the container and visually scan the roof profile — it should be flat or very slightly crowned, not sagging or buckled
• Look for any punctures, deep gouges, or areas where the corrugation has been compromised through the steel
• Surface rust on the roof is normal; rust that has eaten through the panel is a defect
• If inspecting after rain, check the interior ceiling for drip marks — active leaks will be visible

Walls and Corner Posts

• Dents and scratches are cosmetic and expected on used containers — these do not affect WWT rating
• Check corner posts (the vertical steel columns at each corner) for straightness — bent corner posts affect stacking ability and door alignment
• Look for any areas where the corrugated panel has been completely punched through or torn — these are functional defects, not cosmetic ones
• Surface rust is normal; rust that has created holes or severely thinned the steel is not

Bottom Rails and Fork Pockets

• The bottom rails (horizontal steel beams along the base) should be straight and uncracked
• Fork pockets (openings in the bottom rail for forklift handling) should be clear and undamaged
• Check that the container sits level — a twisted or racked frame suggests significant structural stress

Door Inspection Checklist

Doors are the most common source of functional issues on used containers. A thorough door inspection takes 2 minutes and catches most problems before they become post-delivery disputes.

• Open both doors fully — Each door should swing fully open (270 degrees if using door holders) without binding or grinding
• Check door alignment — The gap between the door and the frame should be even and consistent. Uneven gaps indicate a bent door frame or racked container body.
• Test the locking rods — The cam locks on both doors should engage smoothly and lock completely. Stiff or seized cam locks are repairable but worth noting.
• Inspect door seals (gaskets) — The rubber gasket around the door perimeter should be intact, pliable, and fully adhered to the door frame. Cracked, missing, or compressed-flat gaskets allow water ingress.
• Close doors and check the seal — From inside with doors closed (have someone outside), look for light coming through any part of the door perimeter. Any visible light is a potential leak point.
• Test interior release — If the container will be occupied at any point, confirm there is a way to open the door from inside. Standard containers do not have this — it requires modification.

Interior Inspection Checklist

Floor

• Walk the full floor length — it should feel solid underfoot with no soft spots or flex
• Standard container flooring is hardwood (typically tropical hardwood or bamboo composite). Check for rot, deep gouges, or areas where the wood has delaminated from the steel sub-frame
• Container floors are treated with pesticides during manufacture — for habitation use, the floor should be sealed or replaced
• Look for forklift damage: deep gouges or splintered sections from repeated tine contact are cosmetic but worth noting for sensitive storage

Walls and Ceiling Interior

• Check for rust staining or mineral deposits on interior walls — these indicate past water infiltration even if the container is currently dry
• Look at the ceiling corrugations for any areas of significant rust or thinning
• Note any smells — petroleum, chemical, or strong agricultural odors indicate cargo history that may require ventilation or cleaning before use

Light Test

• With doors closed and any vents covered, check for any points of light entry through walls, roof, or door perimeter
• Pinholes of light through surface rust are not necessarily functional leaks — a pinhole through thin rust at a corrugation peak rarely allows water ingress under normal conditions
• Light through door seals or around the door frame perimeter is a more significant finding

What to Do If the Container Doesn't Meet Grade

If a delivered container has a functional defect — active roof leak, doors that won't seal, compromised structural integrity — document it immediately on delivery:

1. Photograph the defect clearly before the driver leaves
2. Note the defect on the delivery receipt before signing
3. Contact your supplier same day with photos and written description
4. Do not refuse delivery without contacting the supplier first — most issues are resolvable without a return

A legitimate supplier will have a documented process for grade disputes. See: What a Legitimate Container Purchase Process Looks Like

Customization to Consider After Inspection

Once you've confirmed the container meets grade, common upgrades that improve function include:

• Lockbox (padlock protector) for security — welded over the door handles to prevent bolt cutter access
• Ventilation — louvered vents cut into the wall to reduce condensation and heat buildup
• Interior shelving — bolt-in or weld-in steel shelving for organized storage
• Lighting — battery, solar, or hardwired interior lighting for access in low-light conditions

For more DIY upgrade options: Top DIY Container Upgrades You Can Do at Home

Related Reading

• What Is a Conex Box? Complete Buyer's Guide
• How Container Grades Affect Price and Longevity
• Military Conex Boxes: Why They're Built to Last
• 20ft Shipping Container Buyer's Guide
• 40ft Shipping Container Buyer's Guide
• ISO Containers Explained: Sizes, Grades, and Use Cases

Key Takeaways

• WWT grade is a functional standard — it guarantees watertight integrity and structural soundness, not cosmetic condition
• Doors are the most common source of functional issues on used containers — test opening, closing, locking, and sealing before or on delivery
• The floor light test (close doors, check for light entry) is the fastest way to identify potential leak points
• Document any defects on the delivery receipt before signing — photographs taken before the driver leaves are your strongest evidence for grade disputes
• Surface rust, dents, and paint fading are cosmetic and expected — they do not affect WWT certification

To buy a graded WWT container with verified delivery, get a quote by ZIP code or call (800) 223-4755.