Polymeric sand can help you achieve a uniform, weed-free patio, driveway or walkway, but it takes some know-how to get long-lasting results. Before you buy, find out where this sand works best, how to chose a quality product, and how to apply it for optimal results.
Beautiful, Durable Paver Joints
Created by Techniseal in 1999, polymeric sand is the modern alternative to the common mason sand traditionally used to fill spaces between pavers on dry laid surfaces. Whereas mason sand remains loose and is prone to washing out, polymeric sand contains binders that allow it to solidify and create a barrier against weeds and insects.
Most polymeric sand mixtures are based on silica sand, making them more like beach sand than mason sand, which is based on crushed stones such as granite and limestone. Some polymeric sands also contain Portland cement mixture.
The secret ingredient, however, is the proprietary polymer. A polymer is a chemical compound made of large molecules connected in repeating chains by chemical bonding. Polyethylene and natural rubber are two examples. Polymeric sand manufacturers add their own polymer to their sand, and when activated with water, the polymer acts like a glue, allowing the sand to bond into a semi-solid matrix within the paver joints.
As a side benefit, this sand comes in a wider range of colors than mason sand. Create a uniform look with a color that matches your pavers or choose a contrasting color for something more striking.
There are a few downsides, though. If you live in a climate prone to frost heave and need to reinstall your pavers frequently, polymeric sand could be more trouble than it’s worth. While the sand has some give, it can crack during extreme freeze and thaw cycles. Because the sand hardens onto the pavers, you’ll need to scrape it off before you can reinstall any displaced pavers.
Polymeric sand works well for sandstone, bluestone, and other common pavers, as well as for brick, but it’s not always ideal for irregular stones due to the risk of water seeping under the stones. The sand is meant for narrow joints, typically not wider than 2 inches, depending on the brand.
On surfaces with wide joints, such as some flagstone walkways, it won’t set correctly. Staining during application is also a risk, but you can largely avoid this problem by carefully brushing the sand off your pavers before you apply water to activate it.
Polymeric sand costs around three times the price of mason sand and still requires some maintenance. Every rain softens the polymer and washes away a small amount of it. When too little polymer remains to hold the sand in place, the sand starts to wash away just as mason sand does.
In theory, an application of polymeric sand can last up to 10 years, but most are effective for around five years. You might start seeing weeds poke through as early as the second year. Any weed that does pop up should be removed immediately to prevent it from ruining the whole joint.
Choosing the Right Sand for You
A higher quality polymeric sand prevents weed growth and insect infestations more effectively and for a longer time. Higher quality products contain finer sand that’s better able to fill in tiny holes and cracks between the pavers. More importantly, they contain a polymer that forms a strong chemical bond.
Polymeric sands with added Portland cement also tend to form a harder, more watertight, and more durable seal. Too much cement in the mix, however, leaves the joint vulnerable to cracking.
Expect to pay a minimum of around $30 for a 50-pound bag of budget polymeric sand or around $60 for something with a stronger polymer. The highest quality sands can run over $200 per 50-pound bag.
Getting the Most from Your Polymeric Sand
Because the exact composition and polymer type varies between manufacturers, proper application methods also vary. Correct application is essential if you expect the sand to do its job and last for the long term, so read the instructions carefully before you start work.
Plan the job for a two- or three-day period of warm, dry weather. The sand needs time to set, and if it is hit with heavy rain too early in the process, you’ll end up with a muddy mess. The pavers should be completely dry when you start.
To apply the sand, pour it out onto the pavers, then use a coarse-bristled push broom to sweep the sand into the joints, working back and forth and applying pressure to ensure each joint is filled completely.
Next, compact the sand to remove air pockets that could interfere with the joint’s performance and reduce its lifespan. The ideal tool for the job is a rolling compactor or plate compactor with a neoprene pad, but if you don’t have either, a 2×4 board and a rubber mallet or hammer also work. Lay the board over several pavers and firmly tap it with the mallet, moving down the length of the board to vibrate the sand into the joints. Work over the entire paved area this way.
Remove excess sand with a leaf blower on the lowest setting held at an angle to avoid blowing sand out of the joints. Aim to get the surface of the pavers clean to prevent staining. The sand should sit around 1/10th inch below the top of the paver or even with the lower edge of the bevel.
Activate the sand by lightly showering the pavers with water according to the manufacturer’s directions. Most sands require enough water to saturate the sand just until the water stops soaking into the joint. The right amount of water is critical. Too much and you’ll wash the sand away. Too little and you’ll only partly activate the polymer, leaving the sand weakly bonded and likely to crack or wash out. Let the pavers sit undisturbed for at least 24 hours and don’t drive on them for at least 48 hours.
By holding off weed growth and insect damage, polymeric sand can give you a pristine patio with a lot less effort compared to traditional mason sand. If you don’t often need to reposition your pavers and don’t mind investing a little more cash and effort upfront, this modern joint filler is worth considering for the long-term benefits.