One is a sealed membrane, the other is a fabric held down at its edges. That single difference drives everything else — where water gets in, what snow does, and how the cover behaves at highway speed. Cost runs the other way: tarps win on price, decisively.

We wrap equipment for a living, so take the enthusiasm with the appropriate grain of salt. What follows is the version with the numbers in it, including the places where a tarp is the better call.

Membrane or fabric — the real distinction

A tarp or fitted cover is woven fabric held down at the perimeter — grommets and rope, a drawstring, an elastic hem — and loose between those anchor points. A heat-shrink wrap is 6 to 12 mil polyethylene welded into one piece, then shrunk 25 to 30 percent so it pulls tight across the whole surface. Not tight at the edges. Tight everywhere. Everything below follows from that.

Read the UV row honestly, because it doesn't favour us: vinyl-coated polyester is documented at five to ten years outdoors, UV-stabilized film at roughly one. If you need something you'll pull on and off the same asset for a decade, buy the cover.

Water: where covers actually leak

The textile industry measures waterproofing as hydrostatic head — how tall a water column a fabric holds before letting water through, in millimetres, under ISO 811 and AATCC 127. Laminated poly tarps test around 1,500 to 5,000 mm when new. Vinyl-coated polyester runs 5,000 to 15,000, because the coating is continuous and the seams are welded rather than stitched.

Which gives the fair version, and it isn't the one on most shrink wrap websites: a new, intact vinyl tarp is genuinely waterproof by that standard. The fabric usually isn't the problem — everything it's attached to is. Stitched seams are perforations in a line, grommets are holes with metal pressed through them, and coating wears over a season. Cover manufacturers' own guides put seams, not fabric, at the root of most field failures. A one-piece film has none of them.

Film has its own weak point, for the record: its overlaps. A US patent on aircraft shrink-film packaging says the weakest portions are the seams, where wind and rain degrade the bond between overlapping sections. Fewer overlaps, better wrap.

Snow: the Ontario numbers

Here the difference stops being theoretical. Snow load is depth times density — fresh snow about 50 kg per cubic metre, settled about 200, wet packed about 400. So thirty centimetres of settled snow is about 60 kg on every square metre, and the same depth wet is about 120 kg. The Ontario Building Code's one-in-fifty-year ground snow load is 1.5 kPa for Toronto, 2.0 kPa for Kingston and 2.4 kPa for Ottawa — Kingston's is roughly 204 kg per square metre, between a third and half a metre of wet snow.

On a draped cover all of that lands in the slack, in the pocket between two tie-down points. The pocket deepens, collects more snow, deepens further. It ends one of two ways: the fabric tears or the grommets pull through, or it melts, pools and finds a seam.

On a taut, pitched surface it slides off instead — the metal-roofing literature documents the mechanism, where a smooth sloped surface releases its snow pack once a film of meltwater forms underneath. The word doing the work is pitched: a wrap built flat on top holds snow like anything else, which is why the frame matters as much as the film. Most of our outdoor storage work is won or lost on that frame.

Wind, transport and the law

A loose cover at highway speed doesn't just flap, it oscillates. That flutter fatigues fabric and stitching, delaminates coatings, tears out grommets and abrades whatever is underneath. Bungees make it worse: elastic permits the movement instead of preventing it. The clearest counter-data is a wind-tunnel test of a competing heat-shrink product — the film held at 160 km/h, the facility's maximum, without flapping or lifting, while conventional tarps failed in the same footage. Vendor-commissioned testing of someone else's product, but it's the best flutter comparison that exists.

Then there's the part that isn't about damage. On 6 April 2018 a truck ran a stop sign near Armley, Saskatchewan and struck the Humboldt Broncos team bus; sixteen people died and thirteen were injured. At sentencing the driver's own counsel told the court he had been distracted by a tarp flapping off the back of the truck and was looking at it in his mirror. The stated cause was failing to heed the stop sign — the flapping tarp was the documented distraction. We won't tell you a tarp caused that crash. But if you've wondered whether a loose cover is only a nuisance, that's your answer.

What Ontario law actually says

Two rules get conflated. O. Reg. 363/04, under s. 111 of the Highway Traffic Act, adopts National Safety Code Standard 10 — cargo securement, a tiedown standard, where a tiedown without a marked working load limit is deemed to have a limit of zero. R.R.O. 1990 Reg. 577, "covering of loads", is the one people assume covers weather. It doesn't — it targets aggregate escaping onto the road.

So neither tells you to protect equipment from rain. What the securement regime does require is that your load and its covering not become a hazard to others — which is where a cover flapping into a mirror stops being only your business. And for the record: shrink wrap is weather protection, not securement. Straps with marked working load limits do that, over the wrap, every time — the same rule applies to everything we wrap for freight and cargo.

Cost, honestly

Tarps are cheaper. A heavy 18 oz vinyl tarp runs a few hundred dollars and is reused for years; a set of six is around US$1,400. Against a service called out per job that isn't close, and anyone telling you otherwise is selling something. If you want the other side of that ledger in detail, we've broken down what industrial shrink wrapping actually costs in Ontario.

The sticker price leaves out the rest of the ledger. Carriers bill a tarping accessorial, commonly US$50 to $100 a load. Tarping takes 15 to 30 minutes for a single lumber tarp, 30 to 60 for multiple steel tarps, longer for an awkward machine, and wind can double it. Cheap poly wears out in one to three years. And tarps are heavy — 80 to 150 pounds, sometimes over 200 — handled on a deck five feet up, on loads reaching twelve.

That last part has a cost. An Ontario WSIB study of transportation claims screened 1,026 and found 352 falls from a truck, trailer or its cargo: 214 strains and sprains, 117 contusions, 101 fractures, with nearly a quarter injured more than once in the same event. That's falls from trucks generally, not tarping specifically — the tarping-specific fatality files come from Washington State. Neither is a clean comparison; both are worth knowing before deciding the cheap option is cheap.

And a third option people forget: a Conestoga or rolling-tarp trailer rolls its cover forward in five to ten minutes with nobody climbing anything, and carriers don't bill a separate tarp fee. It costs more to hire. On repeat lanes it often wins.

When a tarp is the right answer

We'd rather say this out loud than have you find out afterwards.

• The cover comes off weekly. Wrap is single use — buy a cover instead.
• The asset lives outside for years. Premium vinyl outlasts film several times over on UV alone.
• Standard freight on a repeat lane. Lumber, steel, palletized goods — drivers tarp those daily and they're good at it.
• Budget decides and exposure is short. A week in the yard in September is not a winter in Kingston.

We earn our keep on the other side of that list: awkward shapes no cover was cut for, a season outdoors in real snow, surfaces that can't take chafe, and anything that has to be sealed rather than draped.

Frequently asked questions