Artificial turf infill: what it does, and which kinds Northern Colorado weather favors

01Does artificial turf need infill?

Most turf does. The Synthetic Turf Council, the industry’s trade association, says turf with infill is “preferred over systems without infill,” except for special products only made without it. Infill keeps the turf from moving and “provides an even distribution of weight that will minimize the expansion and contraction of turf when the temperature changes” (Synthetic Turf Council, 2013). The council also advises against driving landscape spikes through the middle of a lawn instead.

Motz, a coated-sand maker, lists what enough infill does on a lawn: cushion underfoot, ballast against “unwanted movement or wrinkling of the turf,” support for the blades and “UV protection of the primary backing” (Motz installation guidelines). Two of those count for more here:

• Temperature swings. The Colorado Climate Center describes the plains as having “a large daily and seasonal range in temperature” (Colorado Climate Center). Even weight helps keep turf flat as it warms and cools.
• Sun. The same source says Colorado’s thin atmosphere “allows greater penetration of solar radiation.” Infill covers the backing between the blades.

Some products are designed to go without. ForeverLawn’s specification for its knitted K9Grass Classic+ dog turf says “No infill material is to be used” (K9Grass specification); see pet turf and regular turf. Some putting greens skip it too. For any product, its spec sheet settles it; what a turf spec sheet should say explains how to read one.

02What are the main kinds of infill?

Weight matters because infill is ballast. Envirofill’s data sheet lists its coated sand at 100 to 103 pounds per cubic foot (Motz). A cork maker gives average densities of 190 kg/m³ for its cork, about 12 pounds per cubic foot, and 400 kg/m³ for tire rubber, about 25 (Amorim). Scoop for scoop, cork weighs roughly an eighth as much as coated sand. Zeolite belongs to our dog turf infill guide, because its job is holding urine’s ammonia.

03Silica sand or coated sand: what’s the difference?

Both are sand; they differ in grain shape and coating.

• Grain shape. An engineer writing for sports-field owners says rounded, evenly sized sand is prized for “its resistance to compaction, and for the weight it provides to help hold the synthetic turf material in place” (Perry, Facilities Manager, 2019). Synthetic Grass Warehouse, a turf distributor, says most silica sand is “fractured and angular” and compacts under heavy rain and foot traffic (SGW).
• The coating. Coated sands are rounded grains in an acrylic, polyolefin or other elastic coating, meant to be the whole infill rather than mixed with plain sand. Perry warns that “poor-quality coatings can clump over time.” Motz says its Envirofill has a “highly-rounded quartz core” that resists compaction and “doesn’t require watering or frequent top-off” (Motz).

Neither needs water to work, which is why sand suits a dry climate.

04How do cork, coconut and other organic infills handle Northern Colorado weather?

Not easily. Most of them work by holding water, and this climate takes it away.

• They need moisture. Perry writes that “some of the organic infills are required to maintain a certain moisture content, and irrigation may be required,” though rarely in a place like New England. GreenPlay, which sells a coconut-and-cork blend, says its coconut fibers absorb moisture “from the air resulting from ambient humidity, rainfall or irrigation” (GreenPlay). Here, the Climate Center says, “Humidity is generally quite low,” and the Greeley UNC station averages 14.65 inches of precipitation a year (NOAA 1991–2020 normals). Keeping it damp means running water onto turf; see do you have to water artificial turf.
• The water they hold can freeze. “Because these fields hold moisture, they can be prone to freezing,” Perry says. NOAA’s normals count 150 nights a year at or below 32°F at Fort Collins and 177.7 at Longmont 2 ESE.
• They are light. Amorim, a cork maker, says any infill can float in heavy rain, when “a small part of the infill floats and is shifted by rain water.” The Climate Center says a plains thunderstorm sometimes drops more than 4 inches of rain on one spot in a few hours, and that the plains get “moderate to high wind movement,” with “periodic, severe turbulent winds” near the mountains. No maker we found rates its infill for wind; weight is the closest guide, and organics are the lightest.
• They break down. Perry reports organic-infill fields that “need to be replenished every two to three years” and organic infill that grows weeds. Motz, which sells a walnut infill, says many organics “can decompose, settle, and compact over time” (Motz).

Walnut shell is the exception on water: Perry says crushed walnut shells “do not require an irrigation system,” and Motz says its own “never has to be watered.” Either way, on fields organic infill is “typically a mix of 30 percent organic material and 70 percent sand by weight,” so the sand still does most of the holding down.

05Where do rubber and cooling infills fit?

Rubber. On athletic fields, “the most commonly used artificial turf infill is made from recycled tires,” known as crumb rubber or SBR, according to the Toxics Use Reduction Institute at UMass Lowell (TURI). Longmont chose otherwise for its Dry Creek fields, which use “coated sand in lieu of rubber infill,” and the city credits sand with “lower heat retention” (City of Longmont).

Cooling infills. Shaw describes HydroChill as “a pre-coated infill that bonds to sand,” whose stored moisture evaporates as the surface heats, and notes that “any wet surface can provide short-term cooling” (Shaw). Like organic infill, it has to be wet to work, and the Greeley UNC station averages 58.3 days a year at or above 90°F. Measured results are in how hot does artificial turf get.

06Which infills do Northern Colorado rules name?

• Firestone. Of the town codes we read, only Firestone’s names the infill for a home lawn. It must be “a non-toxic anti-microbial material such as silica sand or acrylic coated sand,” and “Crumb rubber filler shall be prohibited” (Firestone Development Code 16.6.4). The same section sets a pile of 1.75 to 3 inches and a face weight of at least 70 ounces, and a town permit comes first. Cork, coconut and walnut aren’t named. It depends on how Firestone reads “such as” and “anti-microbial”; ask Firestone Planning before choosing an organic infill. Not legal advice.
• Barefoot Lakes, in Firestone. The metro district’s guidelines call for “proper infill for residential application, such as silica sand or ‘Envirofill’ for kid and pet areas” (St. Vrain Lakes Metropolitan Districts).
• Frederick’s parks. Its playground design standards say “Rubber infill is not permitted” and point to coated silica sand (Town of Frederick). That covers park projects, not home yards.

An HOA can set its own rules (HOA approval for artificial turf), and every town’s turf code is in artificial turf rules in Northern Colorado.

07What should I ask an installer about infill?

• Does this turf’s maker require infill, and how many pounds per square foot? A good answer quotes the spec sheet for your pile height.
• Which sand, and what shape? A good answer names the product and grade and says whether the grains are rounded or angular.
• If it’s coated, what is the coating, and is an antimicrobial named on the spec sheet?
• If it’s organic, how will it stay damp, what happens when it freezes, and how often will it need topping up? A plan that includes water and replenishment is an honest one.
• In Firestone, is the infill written on the permit?

Topping up later is in how often to add infill; more hiring questions are in questions to ask a turf installer, and the whole job is on our artificial turf installation page.