A poly tarp is a waterproof cover made from woven polyethylene, a strong plastic. Thin strands are woven into a tight grid, and each side then gets a plastic coating. The coating stops water. The weave stops tears.

Some folks say tarpaulin instead of tarp. A poly tarpaulin, a plastic tarpaulin, and a polyethylene tarpaulin are all the same sheet. Plastic tarpaulins cover hay on farms, and poly tarpaulins show up at campsites, too. A heavy duty poly tarpaulin is just a thick, strong one.

What makes a poly tarp heavy duty? Thickness, weave, and hardware. A good heavy duty poly tarp should feel like more than a thin plastic sheet. Here is what goes into ours:

• Heavy-duty polyethylene fabric. It's high-density and tightly woven.
• 16 mil thick. That is about half the thickness of a credit card.
• 16x16 weave. That means 16 strands per inch, running both ways.
• 8 oz per square yard. A 12' x 16' tarp weighs about 11 pounds.
• Waterproof, mold, mildew and UV-resistant finish on both sides.
• Heat-sealed seams and hems, plus rope-reinforced edges and capped, riveted corners.
• Rust-proof brass grommets every 18 inches. That is a lot of tie-down points.

We call them super heavy duty poly tarps because the specs back it up. A super heavy duty tarp like this handles wind and wet ground better than a thin economy tarp. Super heavy duty tarps like these share one build across every size, so you know what you're getting.

Is a polyethylene tarp waterproof? Yes. The waterproof poly coating on both sides blocks water, and the seams are heat-sealed. So what makes a poly tarp waterproof in real life? Drainage. Pitch it at a slant, because pooled water gets heavy and tugs on the grommets.

Sun is the other enemy. The UV-resistant finish slows fading and cracking, and mold and mildew resistance helps through a long, damp season. Poly doesn't breathe, though, so when you cover firewood, leave a gap at the sides for airflow. Pitched right, a heavy duty polyethylene tarp handles all four seasons.

Plastic tarps and canvas tarps do different jobs. Canvas breathes and can last for years, but it's heavier and needs more care. A heavy duty plastic tarp sheds hard rain, dries fast, and folds small. Canvas suits jobs that need airflow, and our canvas tarps cover that. Heavy duty plastic tarps suit jobs that need a dry cover.

Three look-alikes get mixed up with poly. A polypropylene tarp, sometimes called a polypropylene tarpaulin, is a lighter plastic used mostly for short jobs. A polyester tarp is woven from polyester fiber and coated to shed water. A polyurethane tarp gets its waterproofing from a polyurethane coat. Polypropylene tarps and polyurethane tarps have their fans, but ours are polyethylene, and that's what we mean by poly.

• Camp shelter. Rig a heavy-duty poly tarp over the kitchen or the picnic table. It makes a quick rain fly and a good windbreak.
• Ground sheet. A heavy plastic tarp under your tent keeps damp and grit off the floor.
• Firewood and gear. A poly tarp cover keeps a woodpile dry. It also fits over bikes, mowers, and boats.
• Home and farm. Patch a leaky roof, cover hay, or protect a garden bed through winter.
• Job sites. A waterproof poly tarp wraps materials, catches debris, and blocks wind.

Small plastic tarps, from 6' x 8' up to 10' x 12', are easy to carry and quick to hang. Large poly tarps, like the 20' x 30' or the 40' x 60', cover boats, hay stacks, and whole work areas. Large plastic tarps also make quick roof covers when a repair can't wait. One large plastic tarp beats a patchwork of small ones, since there are fewer seams to fail.

Brown blends into campsites and fields. Black and silver gives you a silver side that reflects sunlight, which helps on boat covers and trailers. Blue comes in select sizes and is easy to spot.

A little care adds seasons to any tarp.

• Pad sharp corners and rough edges before you pull ropes tight.
• Run rope or bungees through the grommets. Snug is enough, because stretched grommets tear out.
• Prop up the middle with a pole so water drains off.
• Rinse off mud with a hose. Let the tarp dry all the way before you fold it.
• Keep it away from flame. Poly isn't fireproof, so stay clear of campfires, stove pipes, and heaters.
• Store it out of direct sun.

Are poly tarps heavy duty enough for winter camping?

Yes, for wind, rain, and snow, if you pitch them right. Slant the tarp so snow slides off, and brush off heavy buildup. A tarp blocks weather but won't hold heat, so keep it well away from a stove.

How long does a polyethylene tarp last?

Many poly tarps last one to four years outdoors. All-day hot sun shortens that. Thicker fabric and a UV-resistant finish help, and so does taking the tarp down and folding it when you're done.

What does mil mean on a tarp?

A mil is one-thousandth of an inch. It measures thickness, not weight. A 16 mil tarp is 0.016 inches thick, and more mils means a thicker, tougher tarp.

What size poly tarp do I need?

Measure what you want to cover. Then add a foot or two on every side for overhang and tie-downs. A 10' x 12' covers a woodpile or an ATV, and a 12' x 16' fits a camp kitchen or a truck bed. For a plastic tarp heavy duty enough to cover a boat, go 20' x 30' or bigger.

Is a poly tarp the same as a plastic tarp?

Yes. Poly tarp, plastic tarp, polyethylene tarp, and poly tarpaulin all describe the same woven, coated sheet. You'll also see it typed backwards: tarp poly, tarp polyethylene, or tarp plastic. Same material every time.