Poly Tarps also known as Polyethylene Tarps are constructed of multiple mesh fabric layers which are then coated by polyethylene sheets. Each manufactured poly tarp is distinguished by the fabrics mesh count and mil. The poly tarp’s mesh count is determined by the number of threads used per square inch. For example, a poly tarp rated at a 10 x 10 mesh count would typically have 10 threads per inch in both a vertical and horizontal direction. The tarps thickness is determined and measured by the mil or thickness of the coating (1 mil = .001 inch (1/1000). The larger the number; the thicker and more heavy duty the Poly Tarp will be. Regular duty Poly Tarps are typically rated at 6 mils and are commonly used for temporary coverage from the outside elements. Heavy duty poly tarps can range from 12 to 23 mils in thickness and are the preferred tarps for canopy frames.
Poly Tarps are often referred to as P.E. Tarps and are sold in either pre-cut sizes or by the roll. Poly Tarps are available in a variety sizes, colors and thicknesses. It is important to note that the actual size of the Poly Tarp will be 4 to 6 inches smaller in each direction than the size listed on the package. This is referred to as the cut and finish size. The difference in the size is the result of the grommet application process. Grommets are the brass, aluminum or metal rings lining the poly tarps and are used to aid in the attaching of the poly tarp to the canopy frame. The spacing of the grommets will vary from one manufacturer to another. Generally, spacing of the grommets will be between 18 to 36 inches. Shorter spacing of the grommets gives strength to the tarp and helps aid in the prevention of extreme movement that is associated with tearing.
In addition to grommets, Poly Tarps have several features that help reinforce the overall strength of the fabric. On each corner of a poly tarp a triangular plastic covering is installed to prevent the grommets from pulling through the fabric. The corners of the poly tarp are subject to the most tension under harsh conditions. Furthermore, during the grommet process a perimeter rope is added before the tarp fabric is folded back on itself and then laminated to create the hem. The combination of the perimeter rope and hem add great strength to the edges of the fabric.