Gravel, sand, dirt, mulch and demolition debris all have the same problem on the road: wind lifts them out of the bed. A rock thrown from an uncovered load can crack a windshield or worse, which is why most states require loose loads to be covered or contained, and why dump trucks carry tarps.
What Texas requires
Texas covers this in Transportation Code chapter 725, "Transportation of Loose Materials." It defines loose material as material that can be blown or spilled from a vehicle by movement or wind. Section 725.021 requires a vehicle carrying it to be built and kept so the load can't blow or spill out, and for commercial motor vehicles, the load must either be covered with a covering secured at the front and back, or carried entirely inside the load compartment. Other states have their own versions; check the rules where you drive.
The federal rule
For commercial vehicles generally, the federal cargo securement rules in 49 CFR Part 393 require cargo to be contained, immobilized or secured so it doesn't shift, fall, leak, spill or blow off the vehicle. A tarp is one of the ways to meet that for loose material.
Why mesh
A solid vinyl tarp on an open dump bed acts like a sail at highway speed. It balloons, pulls at its tie-downs and can tear. Mesh tarps are made of PVC-coated polyester woven open enough that air passes through, so they stay flat, while the weave is tight enough to hold sand and gravel in. That's why dump truck tarps, and the roll-up tarp systems built for them, are almost all mesh.
Sizing a dump tarp
- Measure the top of the bed inside the rails: width and length.
- Width: most dump beds take a 7 ft or 7.5 ft wide tarp.
- Length: 12 to 16 ft for most dump trailers, 18 ft and up for dump trucks.
- Roll-up systems need a tarp made for that system, with a pocket for the roll bar; a plain mesh tarp is tied down at the grommets.
We carry black PVC-coated mesh dump tarps from 7 x 12 to 7 x 22 ft. If your bed is an odd size, send us the measurements.
Why mesh doesn't fly
A solid sheet stretched over an open bed separates two bodies of air: the fast-moving air over the top and the slower, swirling air trapped in the bed. The pressure difference between them lifts the sheet, which is the same effect that keeps a wing in the air. A mesh lets air through its openings, so the pressure on both sides stays close to equal and there's little left to lift it. The weave still has to be fine enough to stop grit, so dump tarp mesh is a compromise between airflow and containment.
Before you roll out
- Load below the top of the sides so the tarp sits on the rails, not on a heap.
- Pull the tarp tight and fasten it front and back, the two places Texas law names for commercial loads.
- Check for wear where the tarp crosses the tailgate and rails; that's where mesh fails first.
Sources
- Texas Transportation Code chapter 725, Transportation of Loose Materials
- 49 CFR 393.100, general rules for protection against shifting and falling cargo (Cornell LII)
- Waste Management, "Cover Your Load" (Texas requirements summary)
- Library of Congress, dump trucks with gravel along the Alcan Highway route, 1942
Written by the TrueTarps team. Questions about your job? Contact us or request a custom tarp.