Stretch wrap is a structural component
Most operations buy film on price per roll, set the wrapper once in 2014 and never touch it again. Film is the cheapest structural element in a unit load and the one most often misapplied.
January 24, 2023 · Coordination desk · 7 min read · Operations
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- Bought on
- Price per roll
- Should be bought on
- Containment force
- Most missed step
- Locking to the pallet
- Commonest fault
- Too much at the top
Film does not hold a load together. It holds a load to the pallet. Those are different jobs and only one of them is usually being done.
Containment force, not layers
The useful measurement is containment force — the actual pressure the film applies to the load, measured with a simple plate-and-gauge tool at several heights. Counting wraps or measuring gauge tells you what you paid for; containment force tells you what you got. Two operations running the same film at the same number of wraps can differ by a factor of three in containment force depending on pre-stretch, carriage tension and wrapper condition.
Measure it at three heights: bottom third, middle, top third. The profile should not be flat. The bottom needs the most force, because that is where the load is attached to the pallet and where shear during transport concentrates. The top needs the least, because excessive tension up there pulls the outer columns of cartons inward off their corners — which is the mechanism we described in our piece on unit load design, and a very common self-inflicted crushing problem.
Locking to the pallet
The single most skipped step. The film must engage the pallet itself — wrapped down over the deck edge and, ideally, through the top deck boards — so that the load and the pallet behave as one object. A load wrapped beautifully but finishing an inch above the deck is a load that will walk off its pallet on the first hard brake.
- Two to three revolutions at the base, engaging the pallet edge, before any upward travel.
- Roped or cabled film at the base on heavy loads — twisting the film into a cord dramatically increases its tensile grip at the critical point.
- Finish the cycle with a downward pass that re-engages the base, not with a tail at the top.
- On block pallets, the gaps between blocks give the film something to key into. Stringer pallets have less, which is one more small argument for block in high-vibration lanes.
A load that arrives leaning did not fail in the middle. It failed at the deck.
The five settings that are usually wrong
| Setting | Common fault | Better |
|---|---|---|
| Pre-stretch | Set low, so film is consumed rather than stretched | As high as the film allows without breaking; measure yield |
| Bottom wraps | One revolution, not engaging the pallet | Two to three, over the deck edge |
| Force profile | Uniform top to bottom | High at the base, moderate in the middle, light at the top |
| Top wraps | Tight, pulling corners inward | Light containment only |
| Film gauge | Chosen to be thick enough to feel safe | Thinner film at correct containment force usually outperforms thick film applied loosely |
Where the pallet comes into it
A wrap programme tuned on square, flat pallets will not perform on out-of-square ones. A unit twisted more than about half an inch across its diagonals wraps unevenly: the film tightens on two corners and slackens on the other two, and the load arrives leaning no matter how good the settings are. This is one of the practical reasons we hold squareness tolerance rather than treating it as cosmetic — it is a wrapping specification as much as a racking one.
Reference tables
The numbers referred to above, in full, so you do not have to take a sentence's word for them.
Footprints
| Footprint | Inches | Millimetres | Construction | Where it lives | Our stock | Per 53' van |
|---|---|---|---|---|---|---|
| GMA 48×40 | 48" × 40" | 1219 × 1016 | Stringer & block | Grocery, general distribution, retail | Deep | 480–560 |
| 48×48 | 48" × 48" | 1219 × 1219 | Stringer | Drums, reels, wire, square loads | Good | 392–420 |
| 48×45 | 48" × 45" | 1219 × 1143 | Stringer | Automotive, tyre | Good | 420–450 |
| 48×42 | 48" × 42" | 1219 × 1067 | Stringer | Telecom, paint, coatings | Good | 440–480 |
| 42×42 | 42" × 42" | 1067 × 1067 | Stringer | Chemicals, drums, paint | Good | 480–520 |
| 40×48 | 40" × 48" | 1016 × 1219 | Stringer | Beverage, rotated GMA | Good | 480–560 |
| 40×40 | 40" × 40" | 1016 × 1016 | Stringer | Dairy, beverage, bakery | Good | 520–580 |
| 36×36 | 36" × 36" | 914 × 914 | Stringer | Compact, display, light goods | Good | 640–700 |
| 32×30 | 32" × 30" | 813 × 762 | Stringer | Retail display, in-store | Limited | 900+ |
| 30×30 | 30" × 30" | 762 × 762 | Stringer | Light goods, display | Limited | 960+ |
| 48×20 half | 48" × 20" | 1219 × 508 | Stringer | Retail half pallet, promotions | Limited | 1,000+ |
| EPAL 1 | 47.24" × 31.50" | 1200 × 800 | Block, 9 blocks | European trade, retail | To order | 540–600 |
| EPAL 2 / ISO | 47.24" × 39.37" | 1200 × 1000 | Block | Europe, Asia, best container fit | To order | 480–520 |
| Asia square | 43.30" × 43.30" | 1100 × 1100 | Block | Japan, east Asia | To order | 460–500 |
| AU square | 44.88" × 44.88" | 1140 × 1140 | Block | Australia, chemical CP series | To order | 440–480 |
Trailer counts are for stacked, unstrapped loads of sound recycled stock and vary with repair thickness. We confirm the actual count on the bill of lading rather than estimating it. Anything not on this list we cut from reclaim — see custom milling.
Grades
| Grade A | Grade B | #1 premium | #2 economy | Custom cut | |
|---|---|---|---|---|---|
| Original boards | All | Some replaced | All | Several replaced | Mixed |
| Companion boards | None | Permitted | None | Permitted | Permitted |
| Stringer plugs | None | Permitted | None | Permitted | Permitted |
| Metal plates | None | Permitted, disclosed | None | Permitted | Permitted |
| Squareness | Within ¼" | Within ½" | Within ¼" | Within ½" | Within ½" |
| Colour uniformity | High | Mixed | High | Mixed | Mixed, fresh saw ends |
| Protruding fasteners | Zero | Zero | Zero | Zero | Zero |
| Moisture ceiling | 19% (15% on request) | 19% | 19% (15% on request) | 19% | 19% |
| Typical service | Retail-facing, export | Internal, bulk | Automation, racking | One-way, yard storage | Odd footprints |
| Relative price | Highest recycled | −18 to −30% | High | Lowest | ≈⅓ of a new build |
| Remaining life | Longest | Shorter — already repaired once | Longest | Shortest | Varies |
Grade A and #1 overlap: we use #1 for units that needed no repair at all and A for units that are cosmetically uniform. Where a customer holds their own written standard, that document governs and supersedes these names.
Load ratings and deflection
| Construction | Static | Dynamic | Racked (unsupported) | Unit weight |
|---|---|---|---|---|
| Recycled GMA 48×40 stringer, sound | 4,600 lb | 2,800 lb | 1,500 lb | 33–45 lb |
| Recycled 48×40 block, sound | 5,200 lb | 3,000 lb | 1,900 lb | 40–55 lb |
| Recycled 48×40 stringer, repaired (B) | 4,400 lb | 2,650 lb | 1,400 lb | 35–48 lb |
| New southern yellow pine, 5 top boards | 4,200 lb | 2,500 lb | 1,400 lb | 33–38 lb |
| New mixed hardwood block, 7 top boards | 6,000 lb | 3,500 lb | 2,400 lb | 48–58 lb |
| Heavy-duty new build, doubled stringers | 9,000 lb | 5,000 lb | 3,800 lb | 62–78 lb |
| Skid (no bottom deck) | 3,800 lb | 2,200 lb | Not for racking | 24–32 lb |
Representative planning figures for sound stock, not engineering certifications. Racked ratings assume the load spans two rails with nothing under the middle. Derate a further 20–30% for dwell times beyond a few weeks, because wood creeps under sustained load.
- Design ceiling: deflection of span ÷ 100 — about 0.4 inches across a 40-inch unsupported span.
- Orientation: rack a stringer pallet across the wrong axis and the deck boards carry the span instead of the stringers. Capacity can halve.
- Creep: wood deflects progressively under sustained load. A unit measured inside tolerance on day one can exceed it after six months in a rack.
- Stiffness, not strength, is the limit. Mixed hardwood outperforms southern yellow pine in racking by more than their strength figures suggest, because it is substantially stiffer.
- Drive-in racking gives a long unsupported span with no support at the leading edge. Derate hard, use block construction, consider full-perimeter bottom boards.
Moisture and dew point
| Moisture content | What happens | Typical source | Freight weight |
|---|---|---|---|
| 6–12% | Indoor equilibrium. No mould risk. Dimensionally stable. | Kiln dried, stored inside | Lightest |
| 12–19% | Safe working range — our standard ceiling. | Covered dry stack | Normal |
| 19–25% | Mould within days to weeks in warm conditions. | Rain-exposed stacks, green lumber | +5–10% |
| 25–40% | Mould rapid, blue stain likely. | Pallets left in the open through a wet week | +10–20% |
| Above 40% | Saturated. You are paying freight on water. | Standing water, flooded yard | +20%+ |
Mould needs free water. Below roughly 19% the water in wood is chemically bound in the cell walls and spores cannot germinate; above it, they can. Heat treatment kills insects and confers no moisture guarantee; kiln drying reduces moisture and is not a phytosanitary treatment. They are separate claims and conflating them causes both mould claims and border holds.
| Air temperature | Relative humidity | Equilibrium moisture content | Dew point — a pallet colder than this will sweat |
|---|---|---|---|
| 68 °F | 30% | ≈6% | ≈36 °F |
| 68 °F | 40% | ≈7.7% | ≈43 °F |
| 68 °F | 55% | ≈10.2% | ≈51 °F |
| 68 °F | 70% | ≈13.1% | ≈58 °F |
| 68 °F | 85% | ≈18.5% | ≈64 °F |
| 55 °F | 60% | ≈11.3% | ≈41 °F |
| 75 °F | 65% | ≈12.4% | ≈62 °F |
Approximate, for planning. Two separate lessons: wood will eventually equilibrate to whatever air it sits in, and any pallet colder than the dew point of your building's air will condense water on itself and then on your cartons. Acclimatise cold stock indoors for four to twelve hours before loading.
Fasteners
| Fastener | How it holds | Relative withdrawal | Correct for | Wrong for |
|---|---|---|---|---|
| Ring (annular) shank | Rings bite into the fibre; withdrawal must tear wood | 1.8–2.2 | Deck boards, repairs, anywhere a fork strikes | — |
| Helical (screw) shank | Threads itself into the fibre as it drives | 1.7–2.1 | Stringers, blocks, hardwood | — |
| Smooth shank | Friction only; wood shrinks away from it | 1.0 (baseline) | Nothing in a pallet | Every pallet joint |
| Staples | Two thin legs, wide crown, large bearing area | 0.5–0.8 | Collar panels, crate sheathing, lids | Deck and stringer joints |
| Galvanised (any shank) | As above, corrosion resistant | As above | Outdoor and wash-down service | — |
Doubling withdrawal resistance roughly doubles the number of trips a unit survives, for a fastener cost measured in cents. We use ring-shank and helical only, and every unit that has been apart is fully re-nailed. The MIBANT bend-angle test is the industry's rough proxy for nail ductility: too brittle and it snaps on impact, too soft and the joint loosens.
Conversions
| Inches | mm | Millimetres | Inches | Other |
|---|---|---|---|---|
| 20" | 508 | 600 mm | 23.62" | 1 board foot = 144 in³ |
| 24" | 610 | 800 mm | 31.50" | 1 cu yd = 27 cu ft |
| 30" | 762 | 1,000 mm | 39.37" | 1 short ton = 2,000 lb |
| 32" | 813 | 1,100 mm | 43.30" | 1 kg = 2.205 lb |
| 36" | 914 | 1,140 mm | 44.88" | 1" = 25.4 mm exactly |
| 40" | 1,016 | 1,200 mm | 47.24" | 56 °C = 132.8 °F |
| 42" | 1,067 | 1,219 mm | 48.00" | 19% MC = mould threshold |
| 44" | 1,118 | 1,016 mm | 40.00" | 32 bf ≈ one GMA unit |
| 45" | 1,143 | 914 mm | 36.00" | L/100 = deflection ceiling |
| 48" | 1,219 | 762 mm | 30.00" | ≈500 units per 53' van |
Decision trees
Recycled, new, or cut down?
- Does a standard footprint fit your carton pattern with no overhang? If yes → recycled.
- If no: does an oversized footprint exist in reclaim that can be sawn to your size? If yes → cut down, at roughly a third of a new build.
- Does anything automated read the pallet's geometry, or do you need ±⅛"? If yes → new build.
- Is the racked load above about 2,500 lb? If yes → new build, mixed hardwood, block construction.
- Is a documented chain of custody for the wood itself part of an audit? If yes → new build.
- Otherwise → recycled, at the lowest grade that survives the journey.
Buy, own a fleet, or rent from a pool?
- Measure your return rate first. Everything below depends on it and nothing else matters as much.
- Below 50% return → your pallet is packaging. Buy recycled one-way and price it as consumable.
- 50–85% return → the messy middle. Buy recycled on a managed programme, with collection on the same movements.
- Above 85% return, with controlled geography → own a fleet and use toll repair to keep your asset numbers.
- Mandated by a retailer's pool, or shipping to hundreds of points needing identical quality → pool rental, and budget for loss charges.
- Wash-down hygiene is a process requirement → plastic, and we will point you to somebody who sells it.
Stringer or block?
- Does it go into racking where you cannot guarantee orientation? Block.
- Do powered jacks enter from the 48" side? Block.
- Automated storage and retrieval? Block, or new.
- Heavy load sitting for months? Block, mixed hardwood.
- European or ISO-metric footprint? Block by specification, not preference.
- Otherwise → stringer: lighter, cheaper, deeper in recycled stock and easier to repair.
Repair or replace?
- Crack crossing a notch, or more than a third of a stringer's depth? Plug, or condemn.
- Three or more stringer repairs already present? Condemn — that is a pallet held together by optimism.
- Four or more deck boards gone on a low-value footprint? Harvest the boards.
- Above 24% moisture? Dry stack first, then decide.
- Contaminated with oil, chemicals or paint? Out of every reuse stream, permanently.
- Otherwise → repair and re-nail fully, at roughly a third of replacement cost.