To protect a parcel from rain and damp, treat the outer packaging as a shell that will probably get wet, and make sure nothing important depends on it staying dry. In practice that means a correctly sized corrugated box, a wrapped or sealed inner layer around the product itself, every seam taped properly, and the label sitting flat on a dry face away from folds and joins. Do those four things and a wet doorstep stops being a problem.
Between October and February plenty of UK parcels spend time outdoors before anyone opens them. Here is what damp does to packaging, and the small changes at the packing bench that prevent it.
What damp actually does to a parcel
Corrugated board is made from paper, so it takes on moisture from the air as well as from direct wetting. As its moisture content rises, the board loses stiffness. A box that felt rigid on your bench can go noticeably soft at the corners and edges after a few hours in a wet roll cage or on a doorstep, and a soft box protects far less than a dry one.
The second weak point is the seal. Carton sealing tape grips the surface fibres of the board, so a damp or dusty surface gives the adhesive much less to hold on to. A seam that lifts is how water gets in and how contents work their way out.
The third is the label. Direct thermal labels are printed by heat onto a coated surface rather than with ink, and that print can fade with prolonged heat, sunlight or friction. Add water and abrasion against a wet cage and a barcode can stop scanning altogether, which usually means a delay rather than a delivery.
Where parcels actually get wet
Most water damage does not happen inside a depot. It happens in the gaps: handovers between building and vehicle, roll cages standing in a yard, and the final few metres to the customer's door.
That last step matters more than most sellers realise. Royal Mail's Safeplace service lets a customer nominate a delivery spot, but that spot has to be a secure, weatherproof area of the property such as a shed, garage or enclosed porch. Royal Mail states that it will not follow the instruction if the item would be exposed to bad weather, and it does not treat bins or doorsteps as safe places. Other carriers apply their own rules. Assume your parcel may sit outside for a while, and pack for that rather than for the depot.
Choosing an outer that copes with weather
No standard mailing outer is waterproof. What varies is how long each one holds up and how much protection it gives while it is wet.
- Corrugated postal boxes. The best all round choice for winter despatch. A rigid box resists crushing, keeps its contents away from the wet outer surface, and buys you time. For heavier or more fragile orders, step up to double wall board. Browse the full postal box range.
- Paper mailing bags and carrier bags. Light, recyclable and excellent for keeping postage down, but paper is still paper. If you use them through the winter, put the protection inside the bag rather than relying on the bag itself. See the mailing bag range.
- Padded and book wrap mailers. Good for flat, low value items where a soaked outer is an annoyance rather than a disaster, but not for prints, cards or textiles that cannot take a damp edge.
If you are unsure which size of box or bag suits a product, the size finder lists every internal dimension we stock so you can pick the closest fit rather than guessing.
Seal every seam, not just the top
The single most useful habit in wet weather is the H seal. Run one strip of tape along the centre seam of the box, then one strip across each end seam where the flaps meet the sides. That closes the three routes water normally takes into a carton. Repeat it on the base, because a parcel spends plenty of its journey standing on a wet surface.
Two practical points about cold weather. First, adhesives bond more slowly at low temperatures, so press each strip down firmly along its whole length rather than tearing and slapping. A dispenser gun applies far more even pressure than hand tearing. Second, bring tape and flat packed boxes up to room temperature before a run, because cold stock is the most common reason seams lift a day later. Our packaging tape range covers 48mm brown, clear, low noise and paper kraft options along with dispenser guns.
Give the label the best chance
A parcel that cannot be scanned is as much of a problem as a parcel that gets wet. Three rules cover most of it.
- Place the label flat on the largest face of the parcel, never bridging a seam, fold or corner where it can lift or crease.
- Do not run tape across the barcode. Tape over a barcode causes glare and refracted light that can defeat a scanner.
- Remove old labels completely if you are reusing a box internally, and only ever have one live address label on a parcel.
Store thermal label rolls somewhere cool and out of direct sunlight. Direct thermal print is heat activated, so a roll left on a radiator or in a sunny window will darken and become unusable.
Build a dry layer inside the box
The inner layer is what actually saves the order. Wrap the product itself rather than relying on the carton, then fill the remaining space so nothing shifts if the board softens in transit.
Bubble wrap gives you a moisture barrier around the item as well as cushioning, which is why it earns its place in winter even on orders that are not especially fragile. Paper based void fill such as crinkle cut shredded paper immobilises contents beautifully, but be clear about what it does: it is a cushion, not a barrier, and it will absorb water rather than repel it. Use it around an item that is already wrapped. The full void fill and bubble wrap range covers both.
Store your packaging stock somewhere dry
This is the step most small sellers skip, and it undoes everything else. Flat packed board draws moisture from the air, so boxes kept in an unheated garage or lock up through a British winter can be weaker by the time you use them, before a single raindrop has landed on them.
Keep packaging stock indoors, off a concrete floor on a pallet or shelf, and away from external walls and roller shutter doors where condensation collects. Rotate older stock to the front. A light crease along the fold lines of a flat packed box is completely normal and does not affect its strength, so do not mistake that for damage.
It matters at the customer's end too. Recycle Now lists card contaminated with foodstuffs, dirt or paint among the items that cannot go into cardboard recycling, so a box that arrives soaked and mud stained is a nuisance to dispose of.
A wet weather despatch checklist
- Is the item wrapped or bagged inside the outer, rather than sitting loose against the board?
- Is the box the closest size available, with 10mm to 20mm of clearance filled with void fill?
- Are the centre seam and both end seams taped, top and bottom?
- Was the tape pressed down firmly along its whole length, not just tacked on?
- Is the label flat on one face, clear of seams and folds, with no tape across the barcode?
- Has the stock been stored indoors and brought up to room temperature?
- For heavier or fragile orders, have you stepped up to double wall board?
Stock up before the weather turns
Most wet weather damage traces back to one of two things: a box that was too big for the job, or a seal that was never going to hold. Both are fixed at the point you order your packaging, not at the point you pack.
Start with the size finder to match a box to your bestsellers, then top up on tape and void fill in the same order. Standard UK delivery is free on orders over £100, or £6.95 below that, with a 3.00pm cut off Monday to Friday.
