Do it Best Blue Poly Tarp 30'x40' - Choose Your Grade for Montana Jobs

The Do it Best 30’x40’ blue poly tarp comes in two distinct versions that solve different problems. The Medium Duty model (SKU 712187) with its 175-grain polyethylene and 10x8 weave pattern handles serious weather protection. The General Purpose version (SKU 767922) at 135-grain with an 8x8 weave covers basic jobsite needs without the extra cost.

Both versions give you 1,200 square feet of coverage — enough to protect a lumber pile, cover equipment, or create temporary shelter. The difference comes down to how much abuse you expect the tarp to take.

Two SKUs, Two Different Jobs

Here’s what separates these tarps:

Specification	Medium Duty (712187)	General Purpose (767922)
Material Weight	175-grain polyethylene	135-grain polyethylene
Weave Pattern	10 x 8	8 x 8
Thickness	4.5 mil	3.5 mil
Tarp Weight	Approx. 23 lbs	Approx. 19 lbs
Grommet Type	Weatherproof Polycarbonate	Reinforced Aluminum

The Medium Duty version offers a significantly tighter 10x8 weave and 4.5 mil thickness compared to the General Purpose model. That tighter weave blocks more wind and resists tearing when branches or tools poke at it. The Medium Duty model also uses polycarbonate grommets for improved weather resistance over aluminum grommets — polycarbonate won’t corrode or weaken in Montana’s freeze-thaw cycles.

Pick the Medium Duty for long-term outdoor coverage, protecting materials through a Montana winter, or anywhere the tarp takes constant wind stress. The General Purpose works fine for temporary coverage, indoor use, or short-duration projects where you’re watching the weather.

Built for Real Coverage

Both tarps share construction features that matter on a jobsite. Heat-sealed hem with polypropylene rope reinforcement means the edges won’t unravel when you cinch it down tight. Double-sided lamination keeps water from soaking through the weave — critical when you’re protecting kiln-dried lumber or bags of concrete.

Grommets every 3 feet on all sides give you plenty of tie-down options. That 3-foot spacing works with standard bungee lengths and lets you secure the tarp without creating huge wind-catch pockets between attachment points. UV-treated material resists breakdown from Montana’s high-altitude sun exposure.

The 30’x40’ size covers serious ground. Construction material protection (lumber, gravel, etc.) ranks as the primary use — one tarp protects a full unit of framing lumber or a small gravel pile. Temporary roof patching or storm protection becomes possible with this much coverage. Ground cover for large renovation projects keeps your workspace organized and materials off wet ground.

Installation That Works

Position the tarp over the target area. Secure the tarp using ropes or bungee cords through the grommets. Ensure the tarp is pulled taut to avoid wind-flapping or water pooling. Ensure laminated surfaces face outward for maximum UV/water protection.

That last point matters — the laminated surface needs to face the weather. Install it backwards and you lose the water-shedding benefit of the coating.

Compatible with standard 1/4” or smaller bungee cords and utility ropes. Skip the cheap tie-downs. Wind stress concentrates at the grommets, and weak fasteners mean torn grommets and loose tarps. Ball bungees work well for semi-permanent installations. Ratchet straps handle high-wind situations but watch the tension — overtightening tears grommets just as surely as wind does.

The Verdict

The Medium Duty tarp earns its keep on jobsites where failure costs money. Protecting materials through unpredictable Montana weather, creating windbreaks during concrete pours, covering equipment between jobs — these applications justify the heavier construction. The polycarbonate grommets alone make it the better choice for multi-season use.

Save the General Purpose version for indoor applications, temporary dust barriers, or quick-coverage situations where you’ll supervise the installation. Four pounds lighter might not sound like much, but it matters when you’re wrestling a wet tarp in the wind.

Neither tarp pretends to be contractor-grade canvas. But for the money, these poly tarps solve real problems. Just match the grade to the job and secure them properly. A well-anchored mid-grade tarp outperforms a premium tarp flapping in the wind every time.

FAQs

What’s the actual coverage area of a 30’x40’ tarp?

1,200 square feet of coverage. That’s enough to protect a small equipment collection, create a large ground cover for renovation debris, or temporarily patch a significant roof section. Remember to account for overlap and tie-down requirements — effective coverage runs about 10% less than the stated dimensions.

Which grommet material handles Montana winters better?

The Medium Duty model uses polycarbonate grommets for improved weather resistance over aluminum grommets. Polycarbonate stays flexible in cold temperatures and won’t corrode from road salt or ice melt chemicals. Aluminum grommets work fine for moderate use but can become brittle and crack during extreme cold snaps.

How do these tarps handle snow loads?

Neither specification mentions snow load ratings. The 4.5 mil thickness of the Medium Duty provides more puncture resistance than the 3.5 mil General Purpose, but don’t expect either to support significant snow accumulation. These tarps work best with steep angles that shed snow naturally. For flat applications under snow loads, consider upgrading to canvas or structural covers.

Will UV treatment actually extend the tarp’s life in Montana?

UV-treated polyethylene resists the accelerated breakdown you’d see with untreated material at altitude. Expect 2-3 seasons of regular outdoor use from the Medium Duty version with UV treatment versus maybe one season without it. The treatment doesn’t make it permanent — these remain temporary coverage solutions.

What about warranty coverage?

Manufacturer warranty details are not explicitly listed in retail documentation. Standard retailer 30-day return policies apply for defects. Contact the manufacturer or seller for specific warranty claims. Like most poly tarps, these carry minimal warranty protection beyond initial defects. Judge them on specifications and price, not warranty promises.