Gaylord wall grades explained
Single, double and triple-wall corrugated — what each one is, how ECT and burst tests rate it, and why wall grade decides how much your box can safely carry.
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Wall grade counts the layers of fluted corrugated between the flat liners. Single-wall has one flute, double-wall has two, and triple-wall has three. More layers means more edge-crush strength (ECT) and burst resistance — so more weight the box carries and more times it can be reused. For most bulk Gaylord loads, double-wall is the standard; go triple-wall for dense product, tall stacks, or multi-trip reuse.
Wall grade → strength → best use
Typical ranges for pallet-sized Gaylord boxes. Actual ratings vary with flute profile and liner weight, but these bands hold across most inventory.
| Wall grade | Construction | Typical ECT | Typical max load | Best use |
|---|---|---|---|---|
| Single-wall | 1 flute layer | 32–44 ECT | ≈ 250–350 lb | Light returns, kitting, one-way |
| Double-wall | 2 flute layers | 48–61 ECT | ≈ 500–1,200 lb | General bulk, most Gaylord loads |
| Triple-wall | 3 flute layers | 67–90+ ECT | ≈ 1,500–2,500+ lb | Heavy, dense product & repeated reuse |
ECT is measured in pounds per linear inch (lb/in). Load figures assume a properly palletized, evenly distributed static load — see our weight-capacities guide for the math.
Single, double & triple-wall — up close
Each added flute layer changes the box's strength, its cost and the interior space you give up. Here's how to think about all three.
Single-wall
One fluted medium between two liners, about ⅛″ thick. Light, cheap and plenty for one-way loads under ~350 lb: retail returns, kitting, apparel and foam. It wears fast, so it's rarely worth reusing more than once.
Double-wall
Two flutes — usually a B/C combination — for roughly ¼″ of board and 48–61 ECT. This is the default Gaylord: the sweet spot of strength, cost and cube for 500–1,200 lb loads. It stacks two to three high and survives a few trips.
Triple-wall
Three flutes — often an A/C/A or B/C/A build — reaching ⅝″-plus and 67–90+ ECT. It carries a ton of dense product, resists forklift abuse, and pays for itself over 5–10 reuse cycles. The trade-off: it's the priciest and steals the most inside space.
The reason more flutes mean more strength is geometry: the fluted medium stands the board off itself like the web of an I-beam, and stacking two or three webs multiplies the vertical stiffness. It also multiplies wall thickness — which is why a triple-wall box gives up 1″–1½″ of interior per side versus a single-wall box of the same outside size. Match the wall to the load and you buy strength where you need it and cube where you don't.
Flute profiles A through F
Flute size sets thickness, cushioning and stacking strength. Double- and triple-wall Gaylords combine profiles — a coarse A or C flute for stacking strength paired with a fine B flute for a flat, puncture-resistant face.
| Flute | Flutes per foot | Board thickness | Best use |
|---|---|---|---|
| A-flute | 33 ± 3 | 3⁄16″ (4.8 mm) | Cushioning & stacking strength |
| B-flute | 47 ± 3 | ⅛″ (3.2 mm) | Puncture resistance, canned goods |
| C-flute | 39 ± 3 | 5⁄32″ (4.0 mm) | General shipping — the default |
| E-flute | 90 ± 4 | 1⁄16″ (1.6 mm) | Retail & print-quality boxes |
| F-flute | 125 ± 4 | 1⁄32″ (0.8 mm) | Compact retail packaging |
Taller flutes (A) cushion and stack; shorter flutes (E, F) print clean and resist crushing. Most bulk Gaylords ride on A- and C-flute layers because stacking strength is the priority.
ECT vs. Mullen burst — what they measure
Corrugated strength is certified two ways. They answer different questions, and knowing which matters keeps you from over- or under-buying board.
Edge Crush Test (ECT)
A slice of board is stood on edge and crushed until it collapses. The result — in pounds per linear inch — predicts how much vertical stacking load the box survives. For palletized Gaylords that stack in a warehouse or trailer, ECT is the number that matters most, because failure comes from compression, not puncture.
Mullen Burst Test
A rubber diaphragm pushes through the board face until it ruptures, rated in pounds per square inch. Burst measures resistance to puncture and rough handling — useful for boxes that take impacts or carry sharp, dense product. A 200-lb burst single-wall roughly corresponds to a 32-ECT board.
Modern buying favors ECT because it ties directly to how boxes actually fail in a stack. Burst still appears on box certificates and matters for drop and puncture risk — but for a loaded Gaylord riding three-high, watch the ECT.
Burst-to-ECT conversion reference
| Mullen burst | Approx. ECT | Wall grade | Typical use |
|---|---|---|---|
| 200 lb | 32 ECT | Single-wall | Light one-way |
| 275 lb | 44 ECT | Single-wall | Heavy single-wall |
| 350 lb | 55 ECT | Single-wall | Max single-wall |
| 275 lb | 48 ECT | Double-wall | Standard bulk |
| 350 lb | 51 ECT | Double-wall | Heavier bulk |
| 500 lb | 61 ECT | Double-wall | Dense product |
| 700 lb | 67 ECT | Triple-wall | Heavy castings |
| 900 lb | 82 ECT | Triple-wall | Very heavy loads |
| 1,100 lb | 90 ECT | Triple-wall | Max-duty & reuse |
These are the widely used carrier-classification equivalents. They're a guideline, not a law of physics — a burst rating and an ECT rating measure different failures, so treat the pairing as a rough translation.
Moisture & humidity effects
Corrugated is strong when dry and weak when wet — this is the single biggest reason a rated box fails early.
Board strength is measured at roughly 50% relative humidity. Push storage to 90% RH and a box can lose 40–50% of its compression strength. A Gaylord rated for 1,200 lb dry may sag under 650 lb after a humid weekend on an outdoor dock.
- Keep loaded Gaylords off concrete floors and away from dock doors.
- Never let boxes sit in standing water or under a leaking roof.
- For humid or refrigerated environments, step up a wall grade or add a liner.
| Relative humidity | Strength kept | Load on a 1,200 lb box |
|---|---|---|
| 50% RH (rated) | 100% | 1,200 lb |
| 65% RH | ≈ 90% | 1,080 lb |
| 75% RH | ≈ 80% | 960 lb |
| 85% RH | ≈ 65% | 780 lb |
| 90%+ RH | ≈ 50–55% | ≈ 650 lb |
| Wet / saturated | < 35% | < 420 lb |
Why triple-wall is best for reuse
Reuse is where wall grade pays off. Triple-wall board — 67 ECT and up — shrugs off the fork nicks, corner knocks and repeated stacking cycles that shred single-wall after one trip. A Grade A/B triple-wall Gaylord routinely makes 5–10 round trips before it's baled, spreading its cost and its carbon across every use.
How to read a Box Maker's Certificate
Look at the bottom of almost any corrugated box and you'll find a round stamp — the Box Maker's Certificate, or BMC. It's the board's birth certificate, and it tells you exactly what the box is rated to do.
The BMC certifies one of two things: a bursting (Mullen) test in pounds per square inch, or an edge crush test (ECT) in pounds per inch. It also states the limits the board is certified within — the maximum size and the maximum gross weight — plus who made it. If a box is being used past those limits, the rating no longer applies, and any freight-damage claim gets harder to defend.
For a loaded Gaylord, the two numbers to check first are the test value (is it ECT or burst, and how high?) and the gross weight limit. If your load pushes past either, step up a wall grade rather than gamble on the certificate.
| Stamp field | What it tells you |
|---|---|
| Test type | Whether the board is certified by Mullen burst (lb/in²) or Edge Crush Test (lb/in). |
| Test value | The rated number — for example 275 lb burst or 44 ECT. |
| Size limit | Maximum sum of length + width + depth (inches) the board is certified for. |
| Gross weight limit | The maximum combined weight of the box and everything inside it. |
| Facings weight | On burst-rated boxes, the minimum combined basis weight of the two liners. |
| Maker & plant | Who manufactured the board — your traceability and quality reference. |
Spec the rest of the box
Wall grade sets the ceiling; capacity math and condition tell you the safe working limit.
Weight Capacities
Turn ECT into a safe static and dynamic load.
Gaylord Dimensions
Standard footprints, heights and volume.
Condition Grades A–D
How used-box wear affects strength.
New Gaylord Boxes
Fresh single, double and triple-wall.
Used Gaylord Boxes
Graded reuse inventory that stacks.
Size Guide Hub
Master charts, conversions and the decision matrix.
Wall grade FAQ
Is triple-wall always the right choice?
What's the difference between ECT and burst rating?
What flute is used in a Gaylord?
How much strength does a box lose when wet?
Where do I find a box's strength rating?
Does wall grade change the box's inside dimensions?
Match the wall to the load.
Send your product and weight — we'll spec the right board.