Box guide
Single Wall vs Double Wall Boxes
Which wall type your parcels actually need, with thicknesses, weights and the trade-offs.
How do single wall and double wall board differ?
Single wall board has one fluted layer glued between two flat liners. Double wall board has two fluted layers and three liners, so it is roughly twice as thick.
The flute is the wavy paper in the middle. It acts like a row of tiny arches, which is why corrugated board resists crushing far better than flat card of the same weight.
Adding a second flute does more than double the thickness. It gives the board a second set of arches, so it holds its shape under a heavier load and takes a harder knock before it creases.
Both types come with kraft or white outer liners, and both can be printed. From the outside, the main thing you notice is the edge: cut a double wall box and you can see the two rows of flutes stacked one above the other.
Thickness and board grades side by side
The thickness you get depends on the flute. These are the boards we use, with approximate thicknesses.
Thickness is not the only factor. The weight of the paper in the liners and flutes also changes how stiff the board feels. When we quote, we choose a grade to suit the size and load you describe.
| Board | Wall type | Approx. thickness | Typical job |
|---|---|---|---|
| E flute | Single wall | 1.5 mm | Small mailers and retail boxes |
| B flute | Single wall | 3 mm | Everyday parcels and lidded boxes |
| C flute | Single wall | 4 mm | Medium parcels and storage boxes |
| BC flute | Double wall | 7 mm | Heavy, fragile or stacked loads |
When is single wall enough?
Single wall covers most of what small businesses send. Clothing, books, cosmetics, stationery and boxed gifts all travel well in it, as long as the box fits closely.
As a rough rule, many packers stay with single wall for parcels up to about 10 kg that will not be stacked under other heavy boxes. We do not publish load ratings, so treat that as a starting point and test with your own goods.
Single wall is also lighter and folds more neatly. On small boxes, under about 150 mm long, double wall can look chunky and make tight folds harder. Our single wall mailer boxes are a good example of where thin board works best.
Close fit matters more than thickness for most light parcels. A snug single wall box with no empty space often protects better than a loose double wall one.
When should I switch to double wall?
Double wall earns its extra cost when the box faces more than a gentle trip. Choose it in these situations.
If only one of these applies, C flute single wall may still do the job. If two or more apply, start with double wall and test from there.
- The packed box weighs more than about 10 to 15 kg
- Cartons sit three or more high in a van or warehouse
- Contents are glass, ceramics or other breakables
- The parcel passes through several depots and sorting machines
- Boxes go into long-term storage where damp or weight builds up
- Goods have sharp corners that could push through thin board
How much heavier is double wall?
Double wall uses more paper, so it weighs more. Take a medium box of 400 × 300 × 300 mm. Empty, the BC double wall version can weigh roughly twice as much as one in B flute.
For one parcel that difference is small, often a few hundred grams. Over a year of orders it can add up, both in postage bands and in the cost of the board itself.
Outside size grows too. BC adds about 14 mm to each outside dimension, compared with about 6 mm for B flute. Check whether that pushes the parcel into a larger size band. Our guide to keeping UK postage costs down explains how those bands work.
The extra weight matters most for businesses sending hundreds of parcels a week. For occasional large shipments, protection usually comes first.
Does double wall cost more?
Yes, a double wall box costs more than the same size in single wall, because it uses more paper and more glue. The exact gap depends on the size and the quantity, and it is shown on your written quote.
Weigh that cost against breakages. Say one parcel in fifty arrives damaged. A replacement, a second delivery and an unhappy customer often cost more than thicker board across the whole run.
A middle path is single wall C flute, about 4 mm. It cushions better than B flute without the full weight of double wall. Our corrugated boxes in single or double wall can be quoted both ways so you can compare.
Ask for both prices on the same quote. Seeing single wall and double wall side by side, at the quantity you actually need, makes the choice far easier than guessing.
How to decide which wall you need
Work through these steps with a packed sample in front of you. Still undecided? Send the packed weight and a line about the contents, and the quote will carry our board suggestion.
- Weigh the packed box, including any wrapping and inserts.
- Note whether the contents can break, bend or leak.
- Decide whether boxes will be stacked, and how high.
- Think about the route: one courier hop or several depots.
- Start with single wall if the box is light, sturdy and unstacked.
- Move to C flute or BC double wall as weight, fragility or stacking rise.
- Order a few samples and test them with real goods before a full run.
Double wall for storage and moving house
Storage boxes face a different test. They do not travel far, but they may sit at the bottom of a stack for months. Over time, damp and weight can soften single wall board and make the walls bow.
For long-term storage or a house move with heavy contents, double wall is the safer choice. Books, kitchen goods and tools are all better in BC board. Our heavy duty double wall boxes are made for those loads.
Keep stored boxes off concrete floors and away from outside walls. Even double wall loses strength quickly if it gets wet.
Label boxes on two sides and on the lid, and write the weight on heavy ones. Whoever lifts them next will thank you.
Single and double wall for different products
Some products almost always need one type or the other. The pairings below come from the kinds of orders we see most often, and they are a reasonable first guess for your own goods.
Clothing, soft toys, paperbacks and boxed cosmetics are single wall jobs. They are light, they bend rather than break, and a close fit protects them well.
Mugs, glass jars, bottles of wine or oil, ceramic vases and small electrical items are better in double wall, or in single wall with a fitted insert. Heavy tools, car parts and kitchenware for a house move should go in double wall every time.
Framed pictures are a special case. The glass needs edge protection as much as thick walls, so use corners or edge strips inside a box that fits closely. Our fragile item mailers with extra support show one way to handle breakables.
Common mistakes with board choice
The first mistake is using double wall for everything. It adds weight, size and cost to light parcels that would arrive safely in single wall.
The second is the opposite: using thin board for heavy goods to save money, then paying for breakages. Weigh a few typical parcels before deciding.
The third is ignoring the inside fit. A thick box with loose contents still lets goods move and break. Fill gaps or add an insert, whatever board you choose, and measure carefully using our guide to measuring a box.
A fourth is judging board by feel alone. Squeeze tests in the hand say little about how a box behaves at the bottom of a stack, so pack and stack a real sample instead.
