Pre-Shipment Inspection Checklist: 10 Checks to Run Before the Container Leaves the Factory

Part of the Roofing Slate Guide's Buying & Importing section — the factory-side counterpart to the receiving checklist you run when the container arrives. The breakage allowance article explains what you're protected from; this one explains how to check the goods before the risk even passes.

Let me set the scene before I give you the list. It's 9 a.m. at a slate factory in Jiujiang, and a 20ft container has just backed into the loading bay. The forklift driver is waiting. The shipping agent's paperwork is on a clipboard by the door. And the man who ordered ten thousand slates for a church roof in Manchester is 9,000 kilometres away, asleep, trusting a digital photograph of a sample he approved three months ago.

I am the man who shows up at that bay instead of him. I've been doing pre-shipment inspections of natural stone for the best part of fifteen years — roofing slate, paving, wall cladding, the odd very heavy dining table. The factories are different, the paperwork is different, but the principle never changes: you can't fix in Hong Kong what you didn't check in Jiujiang. And in all those years, I've only seen one buyer stand at that bay in person. The other hundred or so had the same question, and it's a good one: "I can't fly out there — so what do I pay you to do?"

Here's the honest answer, from the moment I step out of the car to the moment the seal snaps shut. Ten checks, and the order is not random — each one is cheaper to fix than the one after it.

Check 1 — The Crate Count, Before a Forklift Moves Anything

I start at the paperwork desk, not at the crates. The packing list says 21 crates. I count them from the yard — walking the rows, not trusting the tally sheet — and I take a photo of every row so the buyer can count along with me.

Why first? Because once the forklift starts moving the crates into the container, you can never count them again. A crate count is a five-minute check that can't be undone, and it catches the most common quiet crime in this trade: a crate that "fell off the truck" when production ran short, and a packing list that got conveniently re-issued. The invoice says 21 crates, the yard has 20, and the difference is a conversation nobody wants to have after the ship sails.

Check 2 — The Batch Number, in Three Places

This one is my favourite, because it's the cheapest check in the whole job and it finds the most expensive problems. The batch number — the lot number that ties the test report to the actual stone — must appear three times, and match three times:

1. on the test report you approved,
2. on the packing list for this order,
3. and on the crate labels themselves.

If the crate label says batch A and the test report says batch B, then the stone in the container is not the stone the lab tested — and you've just shipped an untested product. This is the check that catches "we ran out of batch A, batch B was close enough" before it reaches your port. I photograph all three side by side, and the buyer's first question when the photos arrive is usually "why didn't anyone tell me this before?" — the answer is the point of the check.

Check 3 — Open One Crate and Measure: Size, Thickness, and the Calliper

One crate, from the middle of the stack, not the easiest one on top. Cut the straps, lift the lid, and measure what's inside. This is where a CNC-dressed product shows its difference: thickness on a CNC line holds to ±0.5 mm — a calliper reading 6.0 mm across the crate means the roof weight you calculated actually arrives. Hand-split slate, the traditional characterful stuff, runs ±1 mm or more, and that's fine as long as the packing list says what it is.

Length and width go on the same list, from the same five tiles. A 500×250 tile that measured 498×250 is not "within tolerance" — it's a different slate, and the size is the one number your roofer will notice before anything else, because a roof built to 500×250 coverage doesn't know how to fix a 247-mm tile. Check five tiles, write all five numbers, and let the buyer see the spread.

Check 4 — Colour: The Batch Row Is Where the Roof Is Won or Lost

Now the hard part of my job: telling you whether the stone matches the sample you approved, without the sun doing half the work for me. I use the natural-light rule: photograph against the same light you'll see on the roof — overcast light, mid-day, not under the warehouse sodium lamps that make every grey slate look black.

The real check is not "is this the colour" — it's "is this all the same colour?" The order asked for one shade; the crate should hold one shade. If the top layer is the sample match and the middle of the crate is a slightly different batch, that's not a supplier trying to cheat you — that's a factory that packed "the close enough" and hoped you wouldn't notice. When I see two tones in one crate, I pull the layer back and we look at how many rows are affected. Then the buyer decides: accept the mix, or push back on the whole crate. Either way, the decision happens before the container leaves.

And the sneakiest thing I check for at this step — waxed or oiled tiles. A coat of wax over a flawed surface makes the stone look rich and hides nothing; it hides the surface. A tile that shines under the warehouse light but goes dull on the roof is not a better slate, it's a treated one. The colour guide explains what a natural slate surface should honestly look like.

Check 5 — The Ring Test on the Sample Row

The whole row. Hold each tile by the corner and tap it with a steel trowel — a clean ring means the stone is sound; a dull thud means delamination or a hidden crack. I tap ten or fifteen tiles in a row, because a bad batch hides in the middle, not in the sample crate the factory shows you. If two of the ten thud, that's not bad luck — that's a problem with that production row, and the fixer needs to know before the container leaves.

I don't just listen for ring vs thud; I listen for the difference between tiles. A row of clean rings that breaks into a dull one tells you where the bad stone is. This is the same check the receiving crew will do at your door, but doing it here — where a bad row can be pulled before it ships — is worth a whole day's travel. The receiving side of this is spelled out in the inspection checklist; here it's the same test, one layer earlier in the chain.

Check 6 — Moisture: The Gate That's Ignored

Nobody does this on the receiving dock, because the damage from a damp slate shows up a year later. But a slate loaded damp carries water into the micro-cracks, the water freezes on the first winter, and the tile splits along a line nobody saw. That's not the sea's fault — that's the loading yard's fault. This is the check I never skip, and I always have a moisture meter in my bag for it.

The rule I work to: moisture content under 0.5% at the time of loading, measured on the stacking face of a packed tile, not on the first tile of the crate that's been airing for two hours. The factory QC guide shows why a serious producer holds this gate and keeps a lab record of it. If the meter reads 8%, the load waits: crates open, tiles get a day of dry air, and the container ships a day later. That one day is the cheapest fix in the whole trade.

Check 7 — The Breakage Count, Done at the Crate, Not at the Port

Here is the part every buyer gets wrong, and I was wrong about it too for my first year. The breakage count belongs at the factory, not at the port. The 1–3% allowance is the threshold for a transit claim — but if you count the broken pieces at the factory, you'll find them at the factory, and they belong to the factory. The breakage allowance article explains the claim side of this number; the inspection side is simpler: I open the crates, count the chipped and cracked tiles while they're still inside the crate, and the number that leaves is the number that was made. Not the number the sea added.

I tell the buyer the honest split: a well-packed crate lands at the port with 0.5–2% broken from the trip; the crate that left the factory with chips already in it — that's the factory's count, not the sea's. When you've bought 1,300 m² and 1% is 104 tiles, the difference between "the sea did it" and "the factory packed it" is the difference between a claim and a quiet correction.

Check 8 — The Loading Pass: One Crate at a Time

Now the container itself, and this is where I do my best work. The loading plan is the packing spec in action, and I watch it crate by crate:

• Base first. The first layer goes down flat, with the heaviest grade at the bottom — a random stacking order makes a top-heavy crate that crushes the one under it.
• Wall to wall. The crates go in braced against the container sides — a gap that lets a crate slide is a gap that becomes a chipped corner.
• The door gap. The last row goes in with a deliberate air gap — the "sacrificial row" that absorbs the worst of the forklift's final pass — and it's blocked so it can't walk.

I photograph every row as it goes in. You'll hear "container loading" and think it's cargo art; the reality is twenty-odd crates of 60 m² each, and the only art is keeping the stack tight enough that the sea can't push it around. The crate and packing standards walk the stacking plan; the inspection is the insurance policy against it.

The door row is where the damage lives. I will not sign a loading pass where the door row isn't blocked, because the door is the first thing the forklift touches and the last thing the crane sees. A single crate standing loose at the door is a crate that's been hit twice and is broken before the ship sails.

Check 9 — The Seal, and the Countdown That Starts When It Snaps

The moment the seal goes on, the clock starts for the buyer's insurance and the claim window (usually 3–7 days from delivery for the carrier, whatever the contract says for the supplier). I photograph the seal number in the crate label context, and the buyer's paperwork gets a photo of it: the seal number is the one number that ties the whole trip together.

The seal does something bigger than close the door: it hands over the risk. FOB or CIF, the incoterm decides who owns the sea leg — and the pre-shipment inspection is the buyer's last chance to see the stone before the risk passes. Once the seal is on, "the container left whole" is a photograph; "the container left wet" is a claim you can't make. The day of the inspection is the day the buyer's photo album of the shipment ends.

Check 10 — The Paperwork: Three Documents and the Warranty

Last, the paper. I check that the packing list matches the crates, the test report's batch number matches the labels, and the invoice matches the quoted specs — the same five numbers as Check 1, now at the end. And then the real question: what happens if the container arrives and something doesn't match? The inspection is only as good as the warranty behind it. A written line in the contract — "over 2% broken in the container, replaced at the contract price; photos with the ruler and the packing list are the evidence" — is worth more than a whole day of my time.

You'll notice I didn't spend a word on "quality control" in the abstract. QC is not a philosophy; it's a sequence. The factory that runs this sequence on every order is a different business from the factory that runs it on the orders it likes. The sourcing guide tells you what to look for in a supplier; this checklist is what to look at when the container is being sealed.

The Downloadable List (and What Each Line Means)

Here's the whole thing on one page — print it, stick it in a notebook, and tick as you go. The right column is the "why" — the number or test that makes each line more than a ritual.

The line between the arrival inspection and this pre-shipment one is simple: at the factory you can still fix it; at the port you can only claim it. Every hour you spend here is an hour you won't spend negotiating later. And if you can't come — well, that's the honest business case for third-party inspection, and it's a whole lot cheaper than a bad container.

Frequently Asked Questions

Related Reading

• Roofing Slate Inspection Checklist — the receiving end: the same checks on the day the container opens
• Understanding Breakage Allowance — the contract lines that decide who pays when the sea does its worst
• Roofing Slate Packaging and Crate Standards — the packing plan the loading pass verifies
• Factory Quality Control from Quarry to Packing — the QC gates that run inside a serious supplier
• How to Read a Roofing Slate Test Report — the batch number and the numbers that prove the stone