Specs & engineering

Deck coverage is not deck strength

Customers ask for more deck boards when they want more strength. Sometimes that works. Often they have bought the wrong upgrade.

April 30, 20246 min readOwen Kessler — Custom Build ShopSpecs & engineering

A fifty-three foot trailer backed onto a yard, loaded floor to ceiling with wood and plastic pallets ready to move.

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In short

Deck coverage — the proportion of the deck area occupied by boards — governs whether small items fall through, how well point loads spread, and how the bottom carton layer is supported. It does relatively little for racked capacity, which is governed by the stringers.

If your problem is sagging in a rack, more deck boards is the wrong purchase. If your problem is bags slumping or pails tipping, it is exactly the right one.

Two tall stacks of reclaimed wooden pallets in a warehouse, stamped and stencilled from previous owners, with shrink-wrapped freight behind them. — Inbound cores waiting on the grading line. Every stencil on those stringers belonged to somebody else first.

Two different load paths

Picture a pallet in a rack, supported only at its two ends. The whole load is transferred through the stringers into the beams. The deck boards are passengers — they carry load *into* the stringers over a span of a few inches, but they are not bridging anything.

Now picture the same pallet on the floor with a drum standing on it. Now the deck boards are doing all the work: the drum's footprint sits on two or three boards, and those boards have to carry that concentrated load down to the stringers a short distance below.

Same pallet, two entirely different problems. Deck boards solve the second one. Stringers solve the first.

What more boards genuinely fixes

Small items falling through. Standard seven-board coverage leaves roughly half-inch to one-inch gaps. Small cartons, pails, bagged fittings and loose parts find those gaps.

Bagged product slumping. A sack drapes into a gap and the load loses its shape, then loses its wrap tension, then leans.

Point loading. Machinery on four feet, a drum, a coil. More boards means more of them share the load.

Bottom carton support. Cartons spanning a gap have their base panel unsupported exactly where the corners need footing.

Automated handling. Conveyors and transfer decks dislike gaps, and some will not accept below a threshold coverage.

What it does not fix

Racked sag. Adding deck boards to a pallet that deflects in a rack is close to money wasted. The stringer is the spanning member. Deepen it, shorten the span with rack decking, or move to block construction.

Notch failure. Deck coverage has no bearing on it at all.

Overhang damage. A fully covered deck that is still smaller than the load does not support the overhanging corners. See the real cost of pallet overhang.

There is also a cost the extra boards do bring: weight. Going from seven boards to eleven adds meaningful mass, which you pay for on every mile of freight.

How to specify it

Coverage is board count times board width divided by deck length. Seven 3½-inch boards on a 48-inch deck is about 51%; eleven boards is about 80%; a solid plywood deck is 100%.

For most palletised cartons, seven is fine. For pails, bags and small parts, nine to eleven. For fine powders, small components or anything that must not shift, a plywood or full-coverage deck is cheaper than the alternative of a fallen load.

You can see the effect on the spec bench — change the board count and both the coverage figure and the lumber estimate move.

Takeaways

Deck boards carry point loads; stringers carry racked spans.
Seven boards is around 51% coverage on a 48-inch deck; eleven is around 80%.
More boards adds weight you pay freight on, every trip.
Racked sag is a stringer problem — adding deck boards will not fix it.

Questions

Asked and answered

How many deck boards should a pallet have?

Seven is standard and adequate for most palletised cartons. Nine to eleven for pails, bags and small parts. A solid plywood deck for fine powders or anything that must not shift.

Will more deck boards increase load capacity?

For point loads sitting directly on the deck, yes. For a pallet spanning open air in a rack, barely — that capacity comes from the stringers.

Written by

Owen Kessler

Custom Build Shop

Prototypes and production runs. Draws the cut lists, tests them against real loads, then argues with the cut lists.

Disagree with something here? That is genuinely useful to us — several of these articles exist because a customer told us we had it wrong. Use the form at the top of the page or write to the yard directly.

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Terms used here

Definitions live in one place so they cannot drift. Full list in the pallet glossary.

Base: The lowest structural layer of a pallet — bottom deck boards or, on a skid, the runners themselves.
Deck board: A horizontal board forming the load-bearing surface of a pallet.
Notch: A cut in the lower edge of a stringer allowing fork entry from the side. Two per stringer on a GMA pallet.
Overhang: Load extending past the deck edge. Reduces carton compression strength at the corners and causes crush damage.
Stringer: A lengthwise structural member, typically 1⅜″ × 3½″, forming the spine of a stringer pallet.