Sooner or later a box fleet spends time outdoors, usually because the yard is the only space available and the boxes are empty so nobody worries. A year later the outermost boxes look chalky, the bottom ones are stained, and the fleet is being scrapped for reasons that have nothing to do with load.
What ultraviolet light does over years
It breaks the surface down, which shows as chalking and then as brittleness at the edges and corners. This is slow: a box in full sun for years will lose impact resistance at its most vulnerable points, and the damage concentrates exactly where the stack load already concentrates. It is not a reason to avoid outdoor storage, it is a reason to expect a shorter life for the boxes that see the most sun.
Rain, and where the water goes
A closed box with a solid lid sheds water well. The problems are the base, where water sits between the runners, and any open cut edge, where it enters the core. Standing water under a stack is worse than rain on top, because it never dries. Keeping stacks on a hard standing that drains, and off the ground on pallets or rails, removes most of the damage.
Placement beats specification
The cheapest durability measure outdoors is orientation and rotation. Put the least-used boxes where the sun is least, rotate the stack so the same boxes are not always on the outside, and keep the base of the stack on something that drains. None of that costs anything and all of it extends life.
Covers: what works and what does not
A close-fitting cover with airflow underneath works. A tarpaulin laid directly over a stack is worse than nothing in many climates, because it holds condensation against the top boxes and traps heat. If a cover is used, it should be a tent shape, not a sheet, and it should not touch the box faces where it can trap water. If a stack lives outdoors permanently, a simple roof structure pays for itself in the first few years.
Cold, ice and trapped water
Water that gets into an open edge and then freezes expands, and repeated freeze and thaw works the edge seal loose. In a cold climate this is the fastest route to edge delamination on an outdoor stack. Sealed edges are close to mandatory if a fleet stores outdoors through a winter, for the same reason they are needed on routes that get washed.
Dunnage in an outdoor store
Foam and felt hold water and grow things. An outdoor store with soft dunnage inside will produce a damp interior regardless of the box, so either the dunnage comes out or the store is covered. Where dunnage must stay in, closed-cell facings dry far faster than open-cell.
How it looks to a customer
A chalking, stained box arriving at a customer’s dock reads as a cheap product, whether or not it is one. If the boxes travel to customers, keeping the ones that arrive looking reasonable is worth the slight extra cost of a covered store. The inspect-and-classify discipline in retiring a box fleet is a useful way to decide which boxes go on customer routes.
How much life outdoor storage actually costs
Rather than guessing, compare the boxes on the outside of an outdoor stack with those in the middle after two years. The difference in appearance and in edge condition is the price of the exposure, and it is usually visible enough to justify a cover or a rotation practice without any further analysis.
Where outdoor storage is unavoidable and long-term, it is worth costing a simple roof structure against the shortened life of the outer boxes. On a fleet of any size the structure often pays back in one replacement cycle, and it also keeps the boxes presentable for customer routes.
What we can do
We build PP honeycomb board boxes with sealed edges and drainage for fleets that spend time outdoors, and we will tell you what an uncovered yard does to service life in your climate. Send us the location and how often the boxes are out.