Understanding Breakage Allowance

The sixty-second version: when a container of roofing slate opens, a small amount of broken tile is normal — the trade's working number is 1–3%, and a well-packed 20ft container usually lands under 2%. The word that actually carries the dispute is not "breakage" but allowance: the contract line that says how much is accepted, on what basis it's counted, and who holds the risk. Understand those three things and 90% of arguments over broken slate are settled before the container opens.

I have been the person who shows up after the bad news. When a contractor calls, the tone is always the same: "the slate arrived and some of it's broken, what do we do?" That's the moment the whole story of a shipment gets written in the next five minutes — not by the invoice, not by the test report, but by the way the tiles are counted, photographed, and read. Most of what people believe about breakage allowances is half true, and the half that's wrong is what costs them the claim.

So let me do this the way I'd walk a claims desk — with a stack of assumptions, each one knocked over in turn. This is the version I wish someone had handed me before my first claim, because nobody in the trade teaches it, and every mistake I describe here I have watched a client make at least once.

Three broken roofing slates laid on a dark cloth with a ruler for scale

The Number: 1–3% Is Real, But Read It Sideways

The first thing everyone wants is the number, so here it is: on a properly packed container of roofing slate, 1–3% of the tiles by count arrive broken, chipped, or unsound. Not 1–3% of the square metres — of the tiles, because slate is counted in pieces on a roof, and the piece is what the roofer runs short of. A 20ft box holding about 1,300 m² of 500×250 slate is roughly 10,400 pieces (8 slates per m² at the standard 500×250 gauge); 1% of that is about 104 tiles, which sounds like a lot of glass until you remember the roof needs every single one in a straight row.

Here's where most people read it sideways. The 1–3% band is not a number to add to your order "just in case." It's a threshold for the claim — the point below which everyone shrugs and above which someone pays. When a supplier quotes "2% breakage allowance," they're not saying 2% is a good number, they're saying: up to this line, the sea is part of the deal; past this line, we owe you tiles. That's the whole meaning of the word allowance.

Two supporting numbers live in the same family: cutting waste (5–10% extra on the roof, because hips, verges and slating around valleys eat slates that aren't broken) and LCL breakage (4–5% when your crates share a container with other people's freight, handled twice more than an FCL load). Different jobs, different numbers — and the reason they're all over this site's buying pages. You need the right one at the right stage, and 90% of the "breakage" arguments I see come from using the cutting waste number to argue a transit claim.

Two cracked roofing slate tiles at a crate corner with a ruler

Myth One — "Breakage Means the Container Was Dropped"

There's a picture people keep: a crane drops the whole box, and the container is a story of broken glass. That almost never happens with slate. A dropped container is a whole-shipment event that makes the news; what you have is corner chips and edge nicks, a tile or three per crate, and they look so small that the receiving crew throws them on the reject pile without thinking.

But corner chips are where the argument actually lives. A corner chip smaller than a fingernail doesn't go on a roof — the slate will flake at the corner and the fixer won't accept it — but it's also the kind of damage the crate was designed to absorb. The same container, the same sea, the same crane, and the damage sits in the range between 0.5% and 4% depending on how the crate was built and how it was loaded. That spread is not luck; it's the packing plan. When you see 8% at the door, the first question is not "was the ship rough?" — it's "was the crate strapped, interleaved, and stacked the way the brochure says?"

Which brings the practical rule: the tighter the crate and the stack, the less breakage arrives. A container that leaves with the crates double-stacked, braced against the walls, and the door row blocked is a container that arrives as it left. That's the packing spec in the article on crate standards — the line between the 1% shipment and the 3% shipment is often a loading detail nobody photographed.

Myth Two: "We Count Broken Tiles and Send the Photo"

This is the one that costs the most, because it sounds right. When the container opens, everyone counts the broken tiles, takes a photo, and sends it to the supplier. And the supplier replies, slowly, with a single question that you didn't prepare for: on what basis?

Three bases, and they settle different things:

Per crate vs per container. If the allowance is "2% of the container," then a single bad crate with 10% broken sits inside a container that's still under 2%. If it's "2% per crate," the same crate is a claim. Most supplier allowances are written on the container; most buyer expectations are on the crate. The first page of any dispute is agreeing which one you're on.
Pieces vs square metres. As said, the band counts pieces. A claim counted in m² while the order is in pieces is a claim that drifts by the tile's area and the thickness of the argument.
Broken vs damaged. The honest rule is: a chipped corner that can't be nailed is broken; a tile with a hairline crack you could install but shouldn't is damaged; a tile that's merely dirty is not a claim. The allowance usually counts "broken" and "damaged" together — but only because the contract says so.

So before you photograph anything, the question is: on what basis are we counting? and the answer had better be in the contract. If it isn't, the other side gets to choose, and they're not the one holding broken tiles.

Myth Three — "The Supplier Pays Because I Paid for It"

This one is closer to true than the others, but the word is not "pay" — the word is risk. In a typical FOB slate shipment, the risk for the goods passes when the crates cross the ship's rail; the buyer owns the transit from there. That's the incoterm, and it is usually the buyer's cargo insurance that covers the sea leg — not the supplier's. The quotation guide walks the FOB/CIF difference in detail; the claims-side version is simpler: the owner of the risk owns the claim.

What the supplier does pay for — and should — is the part of the damage that happened on their side: the crack in the crate that shipped a damp tile, the strap that snapped, the stacking that crushed a corner. That's not transport risk; that's a packing failure, and it's the supplier's. Which is why the good suppliers offer a breakage guarantee — "over 3% in the container and we replace the extra" — and the rest just say "damage happens." That one line separates two very different suppliers, and it's worth asking for before you sign.

Myth Four — "If It's Over 3%, We Send It Back"

Slate is not sent back, it's settled. Shipping a container across the ocean and back for 200 broken tiles is more expensive than the tiles, and no sensible supplier proposes it. What a claim actually does is run one of these paths:

Path	What happens	When it applies
Replace on next order	Broken tiles credited, replacement tiles added to your next shipment at no cost	The normal supplier remedy; keeps the project moving
Credit against the invoice	Dollar credit for the broken m², minus the cost of the allowance itself	When the buyer doesn't need more slate and prefers the money
Freight claim	The carrier's liability for cargo damage during the sea leg, paid by the insurance	Only if the damage is provably from handling, and inside the claim window
Retainage/return	Whole crate rejected and returned or inspected on-site	Only for a single crate at 10%+ damage, or a bad batch — rare, and freight-heavy

Notice the pattern: the three real paths all end in replacement or credit. "Sending it back" is the path nobody takes unless the damage is concentrated and extreme. So the allowance is really a promise about who owes you tiles later, not a promise about a refund today.

A contractor separating broken slate tiles from good ones at a job site

The Part Nobody Writes Down: The Claim Window

Here is the part that decides more claims than the percentage: time. The claim window for ocean damage is short — for the carrier it's written in the bill of lading, often 3–7 days from delivery; for the supplier it's whatever the contract says, and many say "within days of receipt." After that, the container has been sitting at your yard for a week, the broken tiles have been mixed with the good ones, and the answer to "was it like this when it arrived?" is "we don't remember." That sentence is the end of a claim.

So the rule that pays: the day the container opens is the day the count starts, not the day you decide to count. You don't need the whole container — you need one crate opened on the spot, the broken pieces separated and photographed against the crate, the count written, and the rest held. The receiving sequence is laid out in the inspection checklist; the part that belongs to this article is the number: the percentage only means something inside the claim window, and the window is measured from the seal, not from your next visit to the site.

A surveyor's clipboard in front of a sealed shipping container at the factory gate

The Three Contract Lines That Matter More Than the Percentage

Every buyer spends the whole negotiation on the price per m² and the last hour on breakage. Flip it. The allowance isn't a clause; it's three clauses, and they decide 90% of what a "1–3%" actually means. Here is the template you can paste into your order, in the words I've seen settle the claims:

1. Count. "Breakage allowance: 2% of pieces per container, counted as broken or unserviceable tiles (corner chips, cracks, and delamination) at the buyer's warehouse within 7 days of receipt."
2. Threshold. "Breakage above 2% is replaced or credited by the supplier at the contract price; breakage below 2% is accepted as normal transit loss."
3. Proof. "Both parties agree that digital photos of the affected tiles, taken against a reference ruler and packing list, are the record of the damage."

Three lines. That's the entire contract for the thing that makes people angriest about slate. Notice what they do: they fix the count basis (pieces, not m², per warehouse, not per dock), they fix the threshold and the remedy (replacement or credit, not return), and they fix the evidence (photos with a ruler and the packing slip, against the clock). The percentage number — 1.5%, 2%, 3% — is then just a horse you both pick, and the horse matters less than the racecourse.

If you want the line checked against what the supplier's packing list says, the sourcing guide closes the loop on the supplier's side, and the test report guide keeps the stone's quality out of the transport argument. The stone itself — whether it's strong enough to be worth the argument at all — is a separate question that a test report answers before you pay.

An installer holding a chipped slate tile at a roof edge

When the Damage Isn't "Breakage" at All

Here's the sneaky one that turns a "damage claim" into a roof failure a year later. Most of what a novice calls breakage — a cracked tile at the fixing hole, a delaminated face, a tile that crumbles at the edge — is not an impact crack. It's a moisture or quality defect that was invisible at the dock and woke up at the first frost.

A tile that was loaded damp carries water in the micro-cracks. In the container, that water heats and cools, and when the tile reaches the roof and the first freeze hits, the water expands and the tile splits along a line nobody saw. That's why our packing spec holds export moisture under 0.5% and the factory QC guide makes it a gate. When you find tiles cracking a year in, the answer is usually not "the ship did it" — it's "the tile went to sea wet" or "the stone was never good enough for that climate." The breakage allowance doesn't cover that, because the allowance is about the sea, and a wet stone is not the sea's fault.

A broken roofing slate tile held edge-on to a ruler showing delamination layers

Which is the whole point of this article in one line: the allowance covers the trip, not the tile. It's the number that separates what the container is allowed to do from what the stone was supposed to be. Keep those two separate, and the breakage conversation turns from an argument into a check — the check that fits on a page, the way it's spelled above.

FAQ

What is the normal breakage allowance for roofing slate?

1–3% of the tiles by count, and a well-packed 20ft container usually lands under 2%. The number counts pieces, not square metres, and it is the threshold for a claim: below it, the shipping line has done its job; above it, someone owes you tiles. Cutting waste (5–10%) is a separate, on-site number, and LCL shipments run higher, at 4–5%.

Who pays for broken roofing slate in transit?

The risk usually passes to the buyer at the origin under FOB incoterms, so the buyer's cargo insurance owns the sea-leg damage — not the supplier. The supplier owes replacement only for damage that happened on their side: packing failures, wrong tiles, or defects. A supplier who guarantees "over 3% and we replace" is offering more than the minimum; a supplier who says "damage is always the freight line's fault" is telling you the risk is your problem.

How do I claim for broken slate from a supplier?

Count and photograph the broken tiles inside the claim window (usually 3–7 days for the carrier, whatever the contract says for the supplier), keep the packing slip and a ruler in the photos, separate the broken tiles from the good ones, and compare the count to the contract's allowance. Then the remedy is usually a credit or replacement on the next order — not a return, which nobody ships back. The inspection checklist lays out the sequence.

What percentage of slate breaks during shipping?

For a properly packed crate, 1–3% by piece count is the honest band; most well-run shipments land at or under 2%. The spread comes from packing, stacking, and handling — not the sea. LCL freight, which moves twice more, runs 4–5%; anything above that is a packing failure worth an inspection, not a shrug.

Is a chipped corner on slate "broken"?

A corner chip that can't be fixed is broken for the purposes of a roof — the tile will be refused by the roofer. But a hairline crack you could use is damage, and a tile that is present and sound is not damaged at all. The contract defines "broken" and "damaged" and the count basis (pieces vs m²) before the argument — a claim that counts corners as "fine" is a claim that loses.

Should I order extra slate for breakage?

Yes, but from the right column. Add 5–10% for cutting waste on the roof (hips, verges, valleys), and 1–3% for transit breakage on top if you want to be safe. Don't use one number for both, and don't count the "allowance" as if it were extra pieces — it's the threshold before someone owes you tiles, not a separate shipment.