by brittney_cutler | July 5, 2022 4:00 pm
Synthetic grass appears in commercial landscape applications everywhere, from common areas to sprawling lawns, in every venue you can imagine, be it a hotel, business complex, municipality, event space, sporting field, shopping plaza, or apartment complex. It is a frequently used solution for contractors and specifiers who want a landscape that is able to stand up to high-traffic demand, offer enhanced drainage capacity, stay green all year, and require little to no maintenance.
The return on investment (ROI) benefits are also an incentive and include lower water bills; reduced landscaping costs, as there is never a need to mow, resod, or fertilize synthetic grass lawns; and possibly even reduced janitorial costs associated with mud being tracked into facilities. Further, synthetic sod is weatherproof, meaning everyone can enjoy a lawn which stays green year-long regardless of the season. Whether they are used for common areas of an outdoor shopping mall, on the rooftop patio of a commercial office building, or in between pavers to enhance the aesthetics of a hotel, synthetic grass systems provide solutions, and their design and installation are key to project success.
Watering bans and other restrictions
Drought concerns have caused states like Nevada to ban the installation of natural grass in certain applications in favor of drought-resistant landscaping, while California will no longer sell gas lawn mowers or leaf blowers by 2022 as part of the state’s clean energy campaign and pledge to the environment. As new bans and restrictions arise, synthetic grass becomes even more appealing, as it eradicates the need for watering the lawn and offers one-step, 100 percent recyclability, meaning one will never find it in a landfill. This is different than other turf products, which can only be partially recycled due to their urethane backing. Synthetic sod is also low maintenance when it comes to landscaping. Since it does not need to be mowed, lawnmower emissions and noise pollution are eliminated.
Synthetic grass lifecycle and maintenance
The high-traffic yarns of synthetic grass produce resilient surfacing to provide years of low maintenance. The biggest threat to synthetic grass yarn is the sun’s ultraviolet (UV) rays, which break down the yarn and disintegrate the fibers, causing them to get shorter over time. During the yarn extrusion process, plastic pellets are melted down into a liquid and UV-resistant stabilizers are introduced. This additive has a 20-year lifecycle and most additive producers offer a UV protection warranty for 10 years.
So, with an additive which lasts for 20 years and comes guaranteed for 10, how long does synthetic grass last? The real answer has to do with gravity. This fundamental force will eventually affect everything, and synthetic grass fibers are no exception. While specialized yarn is engineered to fight gravity, it is not eternal. Most synthetic grass fields, lawns, and pet yards are made of polyethylene due to its memory properties. Just like the carpet found in most homes, which reacts with indentation after one moves a piece of furniture, these polyethylene fibers have memory and will stand up after heavy use. Eventually, though, with traffic and time, gravity wins, and the surface fibers remain bent. At this point, there is nothing wrong with the performance from a running, playing, drainage, or usage standpoint. The synthetic grass installation simply no longer looks new. One can make use of a rotary broom to brush the sod and alleviate the look of aging fibers. The earlier and more frequent this brushing maintenance occurs the better. Monthly or even quarterly brushing can help prolong the desired aesthetic, and specifiers ought to note this recommendation in their specifications.
How to install synthetic grass
The synthetic sod installation process starts with builders compacting the sub grade (usually dirt), installing a road base layer for stability and then—within this road base layer—embedding drainage to quickly remove surface water, primarily from rain. Builders then install padding if necessary, and finally, they roll out the turf and install an infill of sand or another product to help hold the turf down and keep the fibers erect. While this sounds simple, there are several things to consider.
Drainage, cushioning, and heat
Synthetic sod is a popular choice for sports fields and its design and installation at colleges, universities, high schools, public playing fields, and the like, is an important consideration. Once a specifier has identified a suitable fiber from a traffic and aesthetics standpoint, drainage, cushioning, and heat needs to be addressed.
Most sports fields have a flat grade or are slightly crowned. Architects can design the drainage system for surface slope drains, but in most cases, all that is required is a system beneath the grass to capture water to allow it to flow off the field. Geographic location, rainfall, and snow melt determine how surface water is handled. If necessary for an environmentally sensitive installation, for fields and other applications, builders can use gravels with a higher permeability than road base, which allows the surface water to permeate the ground rather than run off. This is helpful in courtyards of multi-family properties where hardscape calculations are necessary, and many commercial properties in which too much surface water is present.
It is also important to consider sports field cushioning and the desired outcome, as sports use requires a surface soft enough to prevent injury, but not too soft as though playing on a pillow. Soccer differs from football, which differs from baseball in terms of field cushion. Field hockey, rugby, cricket, and many other sports require different cushioning approaches based on how the ball is intended to roll or bounce, how the players impact the surface, and how groundskeepers must maintain these surfaces.
The least expensive and most popular form of cushioning is crumb rubber infill on top of the turf; this can be researched for its many problems including heat, sticking to clothing, splashing up during use, and overall displacement, which requires maintenance. Cost, availability, and ease of install make crumb rubber the go-to product. Other systems use padding between the base layer and the turf. While it costs more to install, this padding eliminates any maintenance as it relates to safety. The padding is set in place under the turf and does not move.
Finally, heat is a major concern for synthetic grass installations, as these surfaces can reach up to 66 C (150 F) and, in some cases, even higher. While some limited technology exists to allow the yarn fibers to reflect sunlight, the research has found a maximum of 20-degree temperature drop benefit at most. Infill products (which are distributed on top of the synthetic turf) can absorb moisture and then slowly release the trapped water through evaporation, which has a great effect on surface temperatures. Irrigation systems can be designed and installed specifically for the purpose of wetting the infill to its saturation point.
When considering synthetic grass installation in sports fields, drainage, cushioning, and heat all need to be addressed during the design phase and properly implemented during installation.
Commercial pet lawns
Commercial pet lawn systems need a turf with a high drain rate, but this is just one variable. Traditional synthetic grass has a urethane backing and must be hole-punched to drain. The urethane-backed turf flow rates are approximately 762 mm (30 in.) per hour, and while this may sound fast, some products can provide more than 25.4 m (83.4 ft) per hour, making pet cleanup much easier.
With this much water flowing, one concern is how to get the water below the turf. Drain tiles are placed between the road base or, in the case of apartments and condominiums, concrete sub-surfacing, to create a void between the turf backing and the sub surface to allow water to freely flow. These tiles are 12.7 to 25.4 mm (0.5 to 1 in.) in height and not only allow for the required vertical drainage to get water below the surface, but also for fast horizontal rates, which send the flow completely out of the area.
It is smart to start with a high drainage rate on the backing and then create a void, which allows the water to flow. Through research and development, synthetic grass producers have identified a few problems with pet excrement and synthetic grass. The ability to clean and flush the surface is determined by two factors: the length of the turf fibers and the amount of infill required.
Most synthetic grass for lawns and sports fields have 44.5 to 50.8 mm (1.75 to 2 in.) and taller fibers. These heights allow for the beautiful look of natural grass, but also allow for cushioning infills as well as the use of cleats on the field to help reduce injury. It is important to place 1.4 to 1.8 kg (3 to 4 lb) of infill on these tall fibers to get them to stand up. This normally results in 19 to 25.4 mm (0.75 to 1 in.) or more of infill. This is a good formula when designing sports surfaces on which a ball ought to bounce and roll, mimicking natural grass. Sports fields have head impact standards, which must be satisfied based on a given jurisdiction’s codes and standards. Each installation must be designed for its intended use. The exact product and the choice of cushioning are determined by the use of the area and the desired playing conditions, both strategic specific to each game and for safety to the athlete.
However, pet parks require a different formula to fit their different needs. Proper pet turf for dogs is 25.4 to 31.8 mm (1 to 1.25 in.) tall and 1417 to 1700 g (50 to 60 oz) thick. This shorter pile height and thickness helps with keeping feces on top of the fibers for easy cleaning. It also allows for less infill to be used, normally just 0.5 kg (1 lb). Less infill means less area to hold onto urine or feces and a shorter distance for flushing through the turf. There are certain types of infill which help. Standard round silica sand is the best infill for most synthetic grass installations. If odor or bacteria is a concern, there are other options. Zeolite is a volcanic ash which traps odors and is used in many applications like horse stalls. Antimicrobial additives have been used in coatings of silica sand to eliminate any bacterial growth. Whether it is a dog park or dog lawn at a pet-friendly hotel, it is important to make sure the turf drainage rate is high, use drain tiles to create a void between the backing of the turf and the sub-surface, choose turf which is short, thick, and designed for pets, and specify the installer only uses 0.5 kg (1 lb) of infill.
There are three types of face yarns in the synthetic grass industry. Face yarn refers to the yarn one sees on top, and thus exposed to traffic. These types are texturized, primarily used in indoor gyms and field turfs, or on putting only golf greens. Monofilament is the prettiest yarn and used for landscape applications or areas where aesthetics takes precedence over function. Finally, there is slit film, which is made for high-traffic spaces. Slit film can stand back up and fight gravity better than monofilament.
One may find an NFL field or two using the prettier monofilament yarns, but these get resurfaced much faster than other municipal applications and are only used a few times per year. Almost all sports fields use slit-film and there is no reason why playgrounds should not do the same. If a church or a school wants a beautiful, low-maintenance lawn by the front door, it should install a monofilament landscape product. Lawns around multi-family properties, senior housing facilities, office complexes, or retail outlets where looks trump utility, choose the prettier turf, but for high-traffic playgrounds, it is better to install slit film yarn.
The other consideration when it comes to playgrounds is impact zones. Every playground equipment manufacturing and installation company specifies a safety zone and fall rating based on the size and height of the design. Synthetic grass utilizes padding below the turf to satisfy fall height and safety impact requirements on playgrounds. Many types of padding from many companies exist for this purpose. The fall height testing data from the padding manufacturer combined with the requirements from the playground equipment manufacturer determines the exact product requirements and the exact area to be covered for the safety surface.
Base settling in high traffic areas can create maintenance issues, but can also be addressed during installation. Normally, a 101.6-mm (4-in.) base is installed to provide stability of the lawn. When designing areas under swing sets or at the bottom of a slide or ladder, where children are impacting the surface hundreds of times per day, installing a thicker base, up to 254 mm (10 in.), in these areas can help reduce any settling which may occur. If these areas do settle over time, they can be raised by removing the problem section of turf and padding, adding base material to level the grade, and then replacing the turf and padding. Specifying an extra 18.6 to 27.9 m2 (200 to 300 sf)—just a 1.4 to 1.9 m (15 to 20 ft) roll—of matching turf be set aside and kept on the property is wise, should the need ever arise.
Quick hits on other surfaces
Bocce ball courts need a thicker base—sand-filled turf at least 38 mm (1.5 in.) tall—so if the player ever throws a lob shot, the surface will not be dented. If texturized yarn is specified, the surface may roll too fast if the court is less than regulation length of 27.4 m (90 ft). In this game, if a ball is rolled and hits the far end without touching another ball, it is deemed out of play. Therefore, installing a surface which is too fast will deliver terrible results. The biggest mistake is installing texturized turf rather than monofilament with the proper sand fill if the size of the court is too small.
When it comes to croquet, turf must be based on court size. If the surface is too fast, the players will not use it very often; therefore, proper speed is the goal. A 1417 or 1700 g turf is necessary to provide enough friction to slow down the balls. The amount and size of sand fill will determine the speed of the roll. This sand fill can be altered and adjusted both in the beginning and during the lifecycle to deliver desired speeds. If the surface is too fast for the size of the court, nothing can be done other than replacing the turf. Further, it helps if the base is laser leveled to ensure a proper playing surface. From the author’s experience with the U.S. Croquet Association and its board, having a surface that is too soft and bouncy will not allow for the necessary jump shots that are a strategic part of the game.
Synthetic golf greens
When it comes to surfacing golf greens, the key is knowing if it will be used for putting only or if the player has space (and a desire) to hit a golf shot into the green. Synthetic grass golf greens, not to be confused with putting greens, need to have a slim-fit turf at least 25.4 mm (1 in.) in height, capable of holding 39 kg (8 lb) of sand per 0.09 m2 (1 sf). Installing an impact pad between the turf and the sub-base is necessary so, after four to five, the green will continue to hold a golf ball, just like a natural grass golf green. Properly designed and installed synthetic grass golf greens can be just as good as their natural grass counterparts without all the maintenance, agronomy expertise, and expensive equipment. The weak links include poor design, due to a lack of golf knowledge; a poorly constructed, bumpy base; and choosing a putting-only golf turf when trying to hit a shot into the surface.
Permeability and erosion
Synthetic grass has a high drainage rate, making it the ideal solution for projects in an area or municipality focused on mitigating run off and erosion. Synthetic grass can easily become 100 percent permeable. Typical installs would use 101.6 mm (4 in.) of a crushed stone aggregate compacted to create a very durable sub-surface. On top of the aggregate to create a smooth base is 12.7 mm (0.5 in.) of dust from the aggregate, which is similar to a paver base.
If permeability and the flow of water is of high concern, a different sub-surface can be created from stone such as the size 57 stone. These stones are about 25.4 mm (1 in.) and come in various shapes to create voids for water to flow. Using landscape fabric to separate the 57 stone from the dust layer is one way to keep the layers separate, but not totally necessary. Using 25.4 mm of dust on top of compacted 57 stone is usually all it takes. Water will flow directly through the turf and this porous base into the soil below.
Erosion is a big issue in many locations out west, where dry climates have very loose soils. Lake Tahoe is one example where construction is limited during a large portion of the year to prevent unnecessary erosion, which can cause landslides and problems for many construction sites where land has been disturbed. By installing synthetic grass where a sub-surface of 101.6 mm and then 38 to 50.8 mm (1.5 to 2 in.) tall turf filled partially with infill is installed, erosion concerns can be alleviated. Turf can slow down the flow of water and the compacted sub-surface base is stable. Eliminating weak links on construction sites of run off and erosion both can be solved with proper synthetic grass design and installation.
Hiring a crew of installation professionals with the experience and knowledge to meet the needs of the developer, architect, landscape architect, specifier, and contractor is crucial.
A good synthetic grass installer will build a great base over compacted dirt and put down the proper drainage, padding, turf, and infill for the use of the space. If the installer is good, they are not biased or swayed by one product or system over another. There is one best system and one best design for the application.
There are turf choices to be made, but for the most part, those are either designed for a specific application or the choice is aesthetic and should be left up to the property owner or end user. Seams between the 4.6 m (15 ft) rolls should be mostly hidden. The infill, and the brushing to install the infill, should result in a surface in which every blade of grass is standing up perfectly. If it is a commercial installation, the edges should be secured for children playing, wheelchair accessibility, and the elimination of trip hazards.
It is imperative the specifier knows and understands the challenges inherent in each site, the goals of the client, and the intended use of the space in order to choose the proper turf product.
Stan Pennington is the founder/CEO of Grass!365, a synthetic grass business with locations across the country. He has a degree in finance and has been designing and installing golf greens and all types of synthetic grass projects in Europe, the Caribbean, and across the United States since 1998.
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