Polymeric Sand; What It Is and How To Use It
Polymeric sand is a granular material placed between the joints or seams in brick pavers or stone in patios, walkways and driveways. It's primary function is to improve the interlock and therefore the durability and stability of a paved surface. Until 4-5 years ago, this function was performed most often with silica or torpedo sand. The sand would be swept between the joints of a brick paver, bluestone or flagstone patio, and it's mere presence would enhance the interlock between pavers or stones. ("Interlock" is another way of expressing a segmental pavement's ability to resist movement via friction between pieces of pavement.) Often that sand would be stabilized by applying a sealer to the pavement; the sealer would help to maintain certain characteristics of the pavers or stone, and would harden the uppermost layer of joint sand, making it resistant to water washouts, ants and weeds.
More recently, sand with polymers added to it has been quickly growing in popularity among contractors. It's use has all but eliminated one of the dreaded customer callbacks: "We had a big storm and a bunch of the joint sand was washed out. Can you drop off a bag of sand for us?" Without the added wait and expense of applying sealer (and the occasional problems associated with sealing brick pavers), the near-perfect prevention of weeds between pavers or stone, washout resistance and strength against ants, for me and other landscape contractors, it's no longer the add-on option for a flagstone or paver project, it's the default choice for joint sand.
Even with that long list of positives, one of the most important wasn't even mentioned; greater durability of the pavement when polymeric sand is used. With polymeric sand in place in a bluestone or brick patio or pathway, water has less opportunity to seep below the hard wearing surface of the pavement (brick or stone in this case) and into the sand and/or crushed stone below. Without water beneath the pavement, silt and fines have no ability to migrate from one area to another, and the drier base and subbase are less likely to deform under traffic loads because water, the Great Lubricator, is nowhere to be found. This means your brick paver patio or flagstone walkway look perfect longer when polymeric sand is used to fill the joints.
With all of those positives of polymeric sand, a detailed discussion about polymeric sand is warranted. Back to Top ^
What Is Polymeric Sand Made From?
The components of polymeric sand vary from manufacturer to manufacturer, but in general, the main ingredients are quartz and crystalline silica (usually 80-95% of the product by volume). Depending on whether the sand has an organic or man-made chemical binder, some include portland cement in their poly sand recipe, but all of them have a proprietary polymer/organic ingredient that is water-activated and acts as the binder between sand particles. It's this polymer that makes this sand so effective. Back to Top ^
How Much Does Polymeric Sand Cost?
The price will vary from dealer to dealer and region to region, but in general you can expect to pay three times more for polymeric sand than you would for a bagged, non-polymeric joint sand (such as silica sand or torpedo sand), or $15-20 per 60lb bag. Considering how having poly joint sand in a project can save on future maintenance expenses (the cost of sand to replace washed out sand, the cost in time and money killing weeds and ants), and reduce callbacks, the expense seems worth the cost. Back to Top ^
I'm Sold. Where Can I Buy Polymeric Joint Sand?
Check with your local brick paver dealers. Most all of the dealers of brand name pavers (like Unilock, E.P. Henry and Belgard) will have at least one brand of polymeric joint sand to sell. Some manufacturers also sell just the polymer, allowing you to buy sand in bulk to mix with the polymer additive. The obvious downside of this is having to ensure that the bulk sand is dry, and having to manually mix the sand on site make this a less popular option. Some installers are even keen on the idea of making their own polymeric-like joint sand mix, though the results appear to be mixed. Back to Top ^
Organic or Synthetic Binder for the Joint Sand?
The key ingredient in any binding paver joint sand is that ingredient that holds the sand together and in place in the joint. Some brands offer an organic binder in their joint sand while others manufacture a chemical binder to stabilize the sand. Installation is the same no matter which type you use, but the performance of the joint sand will differ depending on the binder used, so be sure you use the right sand for the right type of installation.
Organically-bound sands are made using the ground up bits of certain plants. It's that organic matter that acts as the glue for the sand, holding the sand particles together and holding them to the pavers, too. One of the major selling points to organic binder joint sands is also the source of it's greatest weakness; each time water is re-introduced to these sands they re-soften, "self-healing" in any locations where pavers may have shifted or settled and broken the bond with adjoining pavers. But in re-softening to the extent organically-bound joint sands do, they become far less able to resist the germination and growth of weed seeds. Further, the key ingredient in this type of sand, because it is organic, will break down over a period of time, requiring removal and re-application of fresh poly sand.
Those polymeric sands that use synthetic, chemical polymers look and feel virtually identical to their organic counterparts, but their properties differ in a few important ways. Where organic sands have the "self-healing" ability mentioned earlier, sands with man-made chemical binders do not (to any significant degree). The flip side of that is they are much better at resisting weed seed germination and growth, because they don't re-soften as organically-bound poly sands do. Because the chemical binder used is man-made, it does not break down in time like the organic paver sands do. Over time, this means better interlock for pavers, bluestone or even flagstone when chemical polymeric sands are utilized in segmental paver projects. Back to Top ^
Polymeric Sand Color Options
Most polymeric sand manufacturers offer at least two sand colors; tan and grey. And in the last year or two, a few have begun offering varying shades of tan as well as some darker colors, giving hardscapers the opportunity to blend paver work with masonry work that includes colored mortars. In general, color does not affect the price of the sand. Back to Top ^
How To Install Polymeric Paver Joint Sand
Installation of polymeric sand is similar to any other paver joint sand; this is a discussion in our forums of a contractor about to use polymeric sand for the first time. But before you start, make sure there is little or no chance of rain in the immediate future, as polymeric sand will stick to whatever surface it's touching as soon as it gets wet, and is very difficult to clean off the tops of pavers once it's been activated.
Once you've finished laying the pavers, cutting in and installing edge restraint, the polymeric sand is swept into the joints between the pavers and the pavers compacted or tamped. In our operations we sweep and compact the sand and pavers twice, then sweep the sand a third time to top off all the joints. This topping off does one important thing: it eliminates small vertical voids between pavers where weed seeds can land, sit and wait for a little water to start to grow. And even polymeric sand can't stop a germinating weed from growing through the tiniest seam between a sand grain and the side of a paver. So fill those paver joints right to the top before wetting.
Once the sand has been swept in, special care needs to be taken to ensure that no stray sand is sitting on the face of the pavers. Check in corners, along steps and anywhere else sand has a tendency to collect. You can either broom or use a blower to gently clean off that last bit of sand prior to wetting.
Starting at the highest point of your brick (or stone) surface, gently spray a water mist over the paved area, working toward the lowest part of the paved area, lightly soaking the pavers and sand; the objective is to try to wash any remaining poly sand dust or particles off the surface of the pavers while not washing the sand from between the joints. The water mist activates the polymers, which will begin to harden the sand. Most manufacturers recommend allowing the sand to cure/set for 10-15 minutes, then misting the area again with a light spray of water.
The sand may take a full 24 hours to completely activate and harden, but it only takes 20 minutes or so (in a sunny area) for the joint sand to harden off enough that it doesn't adhere to your boots and get deposited elsewhere on the face of the pavers. Back to Top ^
Using Polymeric Sand for Flagstone or Bluestone
Because the joints and seams between pieces of flagstone, bluestone or other natural stone tend to be a good deal larger than the joints between pavers, your approach to joint sand for flagstone may need to be different than it is with brick pavers. In general we've found that most polymeric sands will provide excellent interlock with joints of up to 2" in size. However, other hardscapers have reported the sand doesn't perform as well with joints over 1". In these situations there are several options available:
Purchase the binder only. Mix it on site with larger stone (like stone dust or limestone screenings). The larger stone and binder mix will have a stronger bond for those larger gaps between flagstones.
Use a joint sand made for larger seams. Envirobond (using an organic binder) offers a pre-mixed product that contains both binder and crushed stone, making on-site mixing unnecessary.
It is not necessary to use polymeric sand as the bedding sand for flagstone - if the flagstone was laid correctly, you shouldn't need the extra holding strength of poly sand beneath the stones. Back to Top ^
Frequently Asked Questions About Polymeric Sand
Can I add polymeric jointing sand on top of the joint sand already in place?
For the polymeric sand to adequately firm up in the seams between brick pavers or stone, the full depth of the joint needs to be filled with polymeric sand. Adding a bit of poly sand on top of an existing joint sand already in place will only provide a shallow depth of sand with an activated polymer, making it unable to resist ants, weeds or washout/erosion. If you are retrofitting a patio with poly jointing sand, you should first clean out all existing sand from between the pavers (use a hose or pressure washer), allow it to dry, then apply the poly sand.
Is the dust from polymeric sand harmful?
Checking the MSDS from several polymeric sand manufacturers, they all recommend using some sort of breathing protection while using polymeric sand. It's not known whether the polymer is harmful, but one of the primary ingredients to most poly joint sands is silica (the same as in any silica sand). Prolonged inhalation of silica can cause silicosis, which is an inflammation and scarring of lung tissue which can lead to fibrosis of the lungs and an increased risk of tuberculosis. Silica as not an ingredient unique to polymeric sand and can be found in many other products.
Do I need to use polymeric sand?
Not at all. Polymeric sand entered the segmental paving market less than a decade ago, and many millions of square feet of pavers had been installed prior to the introduction of polymeric sand, and continue to perform well today without it. But the benefits that poly sand brings to a brick paver, bluestone or flagstone installation appear to outweigh the added cost. For those in the hardscaping industry, not using polymeric sand in your installations may result in lost business.
Another option to harden joint sand is to use chemical joint sand stabilizers - most often this comes in the form of a liquid paver sealer. High quality paver sealants are solvent-based (Xylene is often used) acrylics, and it's the acrylic component that both protects the pavers and hardens the joint sand. These sealers don't often penetrate more than ½" into the joint sand, so the acrylic-hardened joint sand may come loose from the pavers if the joint/seam is large enough.
Are there temperatures that I shouldn't apply polymeric sand in?
Most manufacturers specify a minimum ambient temperature (usually above freezing) when installing polymeric sand, and some specify that the temperature be even higher (we've seen as high as 40 and 50 degrees fahrenheit). Applying poly sand in below freezing (or below recommended temperatures) can result in the misted water freezing and damaging the bond being made in the activated poly sand.
Does using polymeric sand guarantee I won't get weeds in my patio?
Nope. Even small relief cut seams in large concrete slabs can be weed farms. Polymeric sand will greatly reduce the opportunity for weed seeds to find a home, germinate and grow, but it cannot eliminate every possibility. Nothing can.
Can polymeric sand be used in high-traffic areas or in vehicular pavements?
Yes. Techniseal even makes what it calls a "high performance" (HP) polymeric sand made for sloped driveways and public pavements.
It sure can. But keep in mind that those "enviro" sands, using an organic binder to harden the sand, will re-soften each time it gets wet, making it susceptible to washout, or in the case of your in-ground pool, "wash-in". Back to Top ^
Polymeric Sand Problems
There are relatively few problems associated with polymeric sand. The most common two we've found are below, as well as their remedies.
Cleaning / Removing Hardened Polymeric Sand From Paver Surface
Most often the need to clean polymeric sand from the surface of patio pavers or stone comes from not following instructions regarding applying or wetting the sand. Sand overflowing joints or piled in corners will quickly harden when wet, and spreading polymeric sand over pavers or stone while they are still wet (possibly from a recent rain) will activate the binder and harden the sand to the surface of the pavers. If the area where the sand has adhered to the tops of the pavers is small, a firm boot scrape may clean the pavers. If the area is larger or has had 24 hours to cure and set, scrub brushes should be used. We've also had members suggest using vinegar as a release agent on the pavers, and it seems to work rather well when combined with scrubbing.
Poor bonding or Poor Interlock
There are rare occasions when either there wasn't enough binder material mixed into the polymeric sand, or for some other reason the polymers in the joint sand failed, causing the sand to act like regular silica or torpedo sand; subject to washouts, ants and weeds. While we've only seen this happen once, other contractors have reported problems more often. In general there is little to be done except to replace the bad sand with new polymeric sand. You might also make a complaint with your sand supplier. Back to Top ^
For most in the industry, polymeric sand provides the landscape contractor a product that can increase the longevity of the brick or stone pavement being constructed as well as reduce callbacks caused by washout, weeds and ants. -gtx