20ft Used Container Inspection Checklist Ontario

By Christian LeBlanc, second-generation operator, and Paul LeBlanc, owner, Van Blanc Ent. Inc.

Reading time: about 14 minutes.

How is inspecting a used 20ft container different from a 40ft?

Inspecting a used 20ft container means walking 8 wall sections, 8 corner castings, a single 6.06m roof panel, both cargo doors, and 41 to 44 floor cross-members. Because a 20ft has half the wall area of a 40ft, each dent or rust spot matters more, and roof pinholes cluster near the door header. A careful walk takes about 20 minutes.

A used 20ft shipping container is inspected differently from a 40ft because the proportions, weight distribution, and failure patterns shift in ways that matter. A 20ft has half the wall area but the same eight corner castings, the same door assembly, and roughly half the cross-members underneath. That changes where you spend your inspection time and which defects matter most.

Three things flip when you move from a 40ft to a 20ft. First, every defect you find counts twice as much per square foot of container, so a one-inch dent on a 20ft is structurally more significant than the same dent on a 40ft. Second, the 6.06m roof span on a 20ft is half the catchment area of a 40ft, which means roof pinholes are rarer per unit but more concentrated near the door header and rear seam. Third, the 20ft is the most-copied size for both legitimate resale and Facebook Marketplace scams, so verification of the unit itself, not just the condition, is part of the inspection.

The framework matches our parent 10-point walkdown we run on every grade at the yard, but the count of things you are inspecting is calibrated to the 6.06m box rather than the generic case. Before you walk a single panel, it helps to picture exactly what a used 20ft is made of.

What are you actually looking at on a used 20ft container?

A used 20ft container is a Corten steel box with external dimensions of 6.06m long, 2.44m wide, and 2.59m tall. Get that picture in your head before you start. Empty tare weight is about 2,300 kg. Maximum gross is 30,480 kg under ISO 1496-1. The interior cubic volume is roughly 33.2 cubic metres.

The corrugated steel sides are not one panel each. They are made of pressed corrugated steel sheets welded together at vertical seams. Most 20fts have two corrugated panels per long side (so four panels across both sides), plus two end panels (one solid end, one with cargo doors) for a total of eight major wall sections you need to walk across.

The underside has steel cross-members spaced roughly 12 to 14 inches apart, running across the 2.44m width. On a 6.06m container that gives you somewhere in the range of 41 to 44 cross-members depending on manufacturer and build year. Each one carries part of the floor load and rust risk.

What does the CSC plate on a used 20ft tell you?

The CSC plate on a used 20ft confirms the container’s identity and certification history. Every legitimate 20ft has a CSC (Convention for Safe Containers) plate riveted to the cargo door frame or the adjacent steel. On a 20ft it sits at roughly chest height on the right-hand door frame as you face the cargo doors. The plate is small (typically 200mm × 100mm) and stamped, not printed.

What you verify on a 20ft CSC plate:

• Manufacturer. Common 20ft builders: CIMC, Singamas, Hyundai, Maersk Container Industry, CXIC, Pacific Container. A name you cannot find through a web search is a red flag.
• Date of manufacture. A 2010-build 20ft in 2026 is 16 years old, near the back end of a typical service life. A 2020-build is essentially mid-life.
• Container prefix and number. Four letters plus seven digits, ending in a check digit. Cross-check with the stencilled markings on the side and the doors. Mismatch is the single strongest sign of a swapped plate.
• Maximum gross weight. Standard 20ft = 30,480 kg. Lower numbers indicate older or non-standard builds.
• ACEP marking. Approved Continuous Examination Programme stamp confirms ongoing certification. Useful but not required for storage-only use.

Take a phone photo of the plate before you walk anywhere else. If the seller is uncomfortable with this, walk away. A real seller treats this as an obvious step. The anti-scam habits we cover in our field guide to spotting container fraud in Ontario apply double on a 20ft, because 20fts are the most-faked size on private resale.

How do you inspect the 8 corrugated wall sections on a 20ft?

You inspect a used 20ft as eight wall sections, not four sides. The order that works best: start at the front (closed end), move down the driver side, around the back (door end) past both cargo doors, up the passenger side, and back to the front.

Spend roughly two minutes per side panel. The vertical weld seams where panels join are the most common location for through-rust on used 20fts because that is where moisture pools when the container ages outdoors. Run a magnet along the seam if you want to confirm steel thickness; bondo or filler under paint will not hold the magnet.

How do you check all 8 corner castings on a 20ft?

A used 20ft has the same eight ISO 1161 corner castings that a 40ft has, but on a shorter container they carry more concentrated load relative to wall area. They are also the single most expensive thing to repair if they are cracked or pushed out of plumb.

The 8 castings, named:

• Top-front-left. Connects roof to door post (or front post depending on orientation).
• Top-front-right. Mirror.
• Top-rear-left. Above the cargo doors, hinge side.
• Top-rear-right. Above the cargo doors, lock side.
• Bottom-front-left. Carries weight when the container is sat on its base.
• Bottom-front-right. Same.
• Bottom-rear-left. Carries forklift and tilt-deck load during delivery.
• Bottom-rear-right. Same. This corner takes the brunt of crane and twist-lock action.

For each casting, check three things: the casting itself is intact (no cracks, no welded repairs unless professionally done), the ISO 1161 holes are clean and undistorted (twist-locks need to fit cleanly for stacking), and the casting is square to the frame (use a level on the side rail). A pushed-in corner means the container was dropped or impacted hard at some point in its service life.

Where do pinhole leaks form on a 20ft container roof?

The roof of a used 20ft is a single corrugated steel panel about 6.06m × 2.44m, sloping very slightly to the long sides for drainage. Pinhole leaks are the number-one lifespan-limiting issue on 20fts in Ontario because we get freeze-thaw cycles that work tiny corrosion points into through-holes over a few winters.

The three highest-risk zones for pinholes on a 20ft roof:

1. Door header seam (rear 50 cm of the roof). Where the roof meets the cargo door header is the most concentrated water-pooling area on a 20ft because the door header is slightly higher than the roof centreline. Walk this zone first.
2. Front-end corner seams (front 50 cm of the roof). Where the roof meets the front end panel sees similar pooling on slightly tilted units.
3. Mid-roof low points. If the roof has a dent from forklift damage or stacking impact, that depression collects water and rusts through within a few seasons.

The inspection method: bring a ladder, climb up, and walk the full 6m length slowly. Hold a flashlight low along the roof surface in raking light to make small dimples visible. Mark anything suspicious with chalk. After you have walked the roof, climb back down and ask the seller to close both cargo doors with you inside. Walk the interior length looking up at the ceiling with the doors closed. Any pinhole you missed from above will show as a pinpoint of daylight from below.

What a 20ft roof pinhole costs to fix in Ontario depends on whether the patch is a simple spot weld or whether the surrounding corrosion has to be ground back, treated, and primed first. A single isolated pinhole is the cheaper end of that range; multiple pinholes clustered in one zone usually mean the whole zone needs treatment, which drives the repair up. If the roof reads worse than the asking grade, it is often smarter to step up to a sounder unit from our in-stock 20ft and 40ft inventory in Brantford than to inherit someone else’s corrosion.

How do you inspect both cargo doors on a 20ft?

The cargo doors on a used 20ft are the most-moved part of the container. They are also where most seal failures happen. Each door is about 2.28m tall × 1.17m wide, and the rubber gasket runs the full perimeter, which means each door has roughly 6.9m of seal length. The two doors together plus the centre seal where they meet add up to about 14m of rubber gasket on a single 20ft. That is a lot of seal to fail.

Door inspection sequence:

1. Open both doors fully (180 degrees). Should swing freely. Binding, scraping, or requiring force suggests frame distortion or hinge wear.
2. Operate cam locks on both doors. Each door has four cam locks (two upper, two lower). All eight should engage cleanly. Stiff or seized cams need lubrication or replacement.
3. Inspect hinges. Each door has four hinges (or three on older builds). Look for cracked welds at the hinge mount and worn pin holes.
4. Compress the gasket. Squeeze the rubber between your fingers along the full perimeter. Should give 3-5mm compression. Rigid, brittle, or cracked gasket = seal failure imminent.
5. Close both doors with a partner inside. Walk the interior perimeter looking for daylight at the seal line. Pay extra attention to the centre seal where the two doors meet and to the bottom seal where dirt accumulates.

Door gasket replacement on a 20ft is one of the most common minor repairs we do at the Brantford yard, and it sits alongside the wider door, lockbox, and conversion work we finish on site before a container is delivered. The rubber itself is inexpensive, and labour adds only another hour or two. If a 20ft passes everything else but the seals are failing, that is a fixable defect, not a deal-breaker.

How many cross-members are under a 20ft floor, and what do you check?

A used 20ft floor sits on roughly 41 to 44 steel cross-members, so slide under the front of the container with a flashlight. Those cross-members run across the 2.44m width, spaced approximately 12-14 inches apart on centre. On a 6.06m container, that spacing works out to the 41 to 44 ribs you will count, depending on manufacturer and build year.

Each cross-member is a structural rib that supports the marine-grade plywood floor above. Cross-members are also the most accessible inspection point because you can see them from below without entering the container. What to check on each:

• Surface rust. Normal on any 10+ year old container. Not a defect on its own.
• Pitting or thinning. Run a screwdriver tip along the cross-member. If steel flakes off easily, the cross-member is losing structural thickness. Look for this especially on cross-members near the door end where moisture from door openings drips through.
• Bending or distortion. Cross-members should be uniformly straight. A bent cross-member means the floor was overloaded at some point in service.
• Prior repair welds. Acceptable if the weld is professional (full penetration, uniform bead). Concerning if the weld is rough or there are multiple repair welds clustered in one zone.
• Floor bolts. Should pass through cross-members at consistent intervals along each. Missing or stripped bolts mean prior floor removal or improvised repair.

The two long steel rails on each side (the bottom side rails) are the primary load path. They are the single most important structural element under the container. Cracks or significant rust on the side rails is a structural rejection. A few patches of surface rust over 41-44 cross-members is normal; consistent thinning across most of them is a sign the container has lived in standing water.

How many plywood floor panels does a 20ft have, and what should each one tell you?

Inside a used 20ft, the floor is marine-grade plywood, typically 28mm thick, laid in panels that span the 2.44m width. The number of plywood panels depends on the panel size used. Most 20ft builds use either:

• 5 plywood panels at ~1.22m length each (the most common modern configuration), or
• 6 plywood panels at ~1.0m length each (older builds and some specialty manufacturers)

Walk the full length of the floor inside the container in deliberate, heavy steps. You are checking each plywood panel for:

• Solid feel underfoot. Sound plywood will not flex more than 5-10mm under your weight. Spongy or springy = water damage.
• Visible water staining at panel edges. Long-term moisture exposure shows at the seams between panels first.
• Pesticide or chemical staining. The factory pesticide treatment is normal (usually BASILEUM SI-84 or TAELILIUM in modern builds). Unknown dark stains may indicate previous cargo contamination.
• Replaced panels. Professionally replaced panels are acceptable if the replacement is the same thickness and properly sealed at the edges. Replacement with thinner panels is a structural compromise.
• Missing or stripped bolts. Floor bolts should be present and tight every 12-14 inches matching the cross-member spacing underneath. Loose bolts let plywood move and rot faster.

If 4 out of 5 plywood panels are solid and 1 is spongy, that is a panel replacement, not a deal-breaker. If 3 or more panels are compromised, the floor is at end of life and you are looking at a full floor replacement, which on a 20ft is a significant job that can outweigh what the unit is worth.

What is the full 20-minute inspection walk in order?

This is the inspection sequence we recommend for a used 20ft. It runs about 20 minutes for an experienced buyer and 35 to 45 minutes if it is your first one. Bring a flashlight, a ladder, chalk, a phone for photos, a measuring tape, and a partner if possible.

1. Photograph the CSC plate (2 min). Verify container number against stencilled markings on the doors and sides.
2. Walk all 8 wall sections (4 min). Front end, driver side front, driver side rear, both doors, passenger rear, passenger front. Mark anything suspicious with chalk.
3. Inspect all 8 corner castings (3 min). Starting with bottom-rear-right (the early warning indicator), then the other seven.
4. Climb the ladder and walk the 6m roof (3 min). Door header seam, front seam, mid-roof. Flashlight at low angle for raking light.
5. Inspect both cargo doors (3 min). Open fully, operate cam locks, compress gaskets, hinge check.
6. Slide under and inspect 41-44 cross-members (3 min). Plus the two side rails. Screwdriver test for thinning.
7. Step inside, close doors, look for daylight (1 min). Walk the interior perimeter with all light off. Daylight = seal or wall leak.
8. Walk the floor in heavy steps (1 min). Identify each spongy panel.

At the end of the walk you should be able to state, to the seller’s face, the specific defects you found and the grade you believe the container actually merits. Negotiate price down based on observed defects, or walk away if the gap between claimed grade and observed condition is too large.

What 20ft red flags mean you should walk away?

Some defects on a used 20ft are repairable, and others are structural rejections. The walk-away list for a used 20ft in Ontario:

• No CSC plate, or plate that does not match stencilled container number. Stolen or fake unit.
• Through-rust holes in any of the 8 corner castings. Structural failure.
• Cracked welds at corner castings or door posts. Frame is no longer load-rated.
• More than 3 spongy plywood panels (out of 5-6 total). Floor is at end of life. Whole-floor replacement makes the container uneconomic.
• More than 5 pinhole leaks in the 6m roof. Pattern suggests the whole roof zone is corroded, not just isolated points.
• Bent or distorted bottom side rails. Primary load path is compromised.
• Cargo door that requires force to operate or shows visible warp. Frame distortion from impact or dropping.
• Recent uniform overpaint with no underlying inspection access. Fresh paint over a used unit is often hiding through-rust. Demand to see unpainted reference areas.
• Seller refuses photographic verification of the CSC plate or the container itself. Almost always a Facebook Marketplace scam.

The single most common scam pattern in Ontario right now: a used 20ft listed below market on Facebook Marketplace, with photos that do not match the actual unit, payment requested in advance by e-transfer, and no in-person yard visit allowed. The pattern is documented across the province in 2026. The defence is the same as it has been since 1995: buy from a seller who lets you walk the container before you pay.

Christian on inspecting 20fts at the Brantford yard

Christian: “The 20ft is our most-sold size in Ontario because it is the size that fits a residential driveway and an agricultural back forty. So we see more 20fts than any other length, which means we have seen every failure mode they have. The corner casting cracks from dropping. The plywood sponge from greenhouse moisture. The roof pinhole from a forklift dent that pooled water for three winters. Every one of those defects is on this checklist because we have written it from the things we actually find on 20fts that come back to the yard. If a buyer wants to walk one with me before they decide, that is what the Brantford yard is for. Worth the drive.”

Most used 20fts at the Van Blanc Brantford yard fall into the two used grades we break down in how each container grade actually differs: Cargo Worthy or Wind & Watertight. CW units pass an inspection equivalent to the one in this guide and are suitable for export or high-density industrial storage. WWT units have visible cosmetic wear but seal against weather. Both can be walked in person at 90 Morton Ave E before purchase. Our step-by-step buyer’s walkthrough for first-time purchasers covers grade selection in more depth.

Frequently Asked Questions

Sources

Reach Van Blanc in Brantford

We have been supplying shipping containers across Ontario since 1995. Our warehouse is at 90 Morton Avenue E in Brantford, and we deliver right across the province with fast 1-3 day delivery from our 4 Brantford yards. Every quote comes with a real lead time, not a hopeful one.

Van Blanc Ent. Inc., 90 Morton Ave E Unit 1B, Brantford, ON N3R 7J7. +1 888-509-6658

Walking a used 20ft yourself takes 20 minutes and saves you from scams and post-delivery surprises that cost far more than the trip. Christian or Paul will walk a 20ft with you at the yard before you pay a dollar. Worth the drive.

Related Reading

• the general 10-point pre-purchase inspection we run on any size
• the basics of used container purchases
• what Cargo Worthy condition really means for Canadian buyers
• when a Wind & Watertight unit is the right call
• how container fraud works and how to recover from it
• reading and verifying a CSC plate step by step
• the defects that should end a deal on the spot