How to avoid hazardous turf seams.

The Problem -- An artificial turf football field, playground, landscape, putting green, or other sport and recreational surface is only as good as its joined seams because, historically seams are the weakest link of a good synthetic turf installation. Joined seams are subjected to high stress from athletic activities; maintenance vehicles; vandalism; and dimensional movements due to changes in weather conditions. A seam break, whether it be accidental due to high stress or an intentionally cut seam by vandals, can cause a completely loose field; tripping or injury due to an open seam; or numerous other hazards.

Seaming Methods -- The two most widely used and acceptable methods of joining seams are to glue them together on top of a wide-width, adhesive-coated fabric or other adhesive-coated subsurfaces and/or sew them together. Benefits more than double when both are done. However, it's often either sewing or adhesive but not both.

It is an accepted fact that an assembly is less likely to break if the stress is distributed evenly over a large area. That's one reason why the role of adhesives is increasing at some expense to mechanical fasteners that concentrate stress.

With mechanical fasteners, holes are made in both surfaces and the fastener passed through them for joining and securing. Stress is concentrated at the point of fastening. Some examples of mechanical fasteners are rivets, nuts/bolts, wire, thread, staples, cord, etc. Sewing is an example of thread or cord being used as a mechanical fastener.

With adhesives, the bond is spread over a much larger area--thus reducing localized stress. That's one reason why from a seam standpoint, total gluedowns are the best because stress from athletic activities and weather changes is distributed over the entire field instead of concentrating it only at the joined seams. Total glue downs also prevent game line movement ("dancing lines" in trade jargon), plus it helps prevent turf from lifting and blowing away in high wind conditions such as hurricanes, typhoons, tornados, dust and sand storms.

However, most (but not all) of the newer type fields which fill the turf matrix with sand and/or rubber granules are not glued to a solid base but instead rely only on glued or sewn seams to hold it together. Broken seam--loose field.

With glued seams, the wider the tape and adhesive on it, the greater the seam strength and stress distribution. With sewing, the quality of the sewing and durability of the thread are very important provided the thread is not cut. In either case, fixing a broken seam on a loose-lay field is a major effort compared to a total gluedown field.

Special Outdoor Adhesives Required -- Because of stress and attack from outdoor exposure, short-term lab tests and a few field tests cannot always be relied upon to predict an adhesive's worldwide, long-term exterior durability for seaming and/or total gluedowns. Good short term results may become long term "time bombs". Also, there is much more to a good outdoor adhesive than just durability after cure, such as easy handling and installation properties.

Installation -- The adhesive must also have three key handling properties for economical installations. It must be usable under widely variable weather conditions; have high green strength due to its tacky, tenacious gripping properties (high grab) to overcome wind, rain and turf curl during installation; and a "wide outdoor working-time window". That's some reasons why for over 25 years, a growing family of one-part, high green strength urethane adhesives have been used worldwide more than epoxy, hot-melt, or both one and two-part, oily, slippery, low-green strength urethane adhesives.

Cost -- "Saving pennies" on adhesive can ultimately cost a fortune but there are still those that insist upon buying cheap/low quality adhesives. Secondary to low price are the adhesive's long term exterior durability and installation handling properties in variable outdoor weather. Hence, neither the contractor nor customer benefits from the "savings" if it results in a failure and/or if it lengthens installation time.

In summary, for seam reliability, our order of preference is: total gluedown with both glued and sewn seams; total gluedown with glued seams on wide tape; loose-lay with glued seams on wide tape; loose-lay with sewn seams; and loose-lay with just edge gluing. Additionally, when gluing, select a proven one-part, high grab urethane adhesive with handling properties designed to fit the system being installed.

by Norris Legue, Synthetic Surfaces Inc.