Polymeric Sand: Controlling Weeds Between Pavers

Over the last fifteen years or so, I have installed numerous brick and stone patios, walkways and driveways. Here in Michigan, most paving is dry-laid, that is, there is no concrete or mortar involved in the installation process. Because concrete and mortar tend to break up over time due to the freeze thaw cycles in this cold climate, it makes sense to use a flexible base and joint filler. Until a few years ago, I used either baby sand, which tends to washed out too easily, or rough-graded sand to fill between concrete or clay pavers. I used chips n dust or stone dust or slag sand to fill between natural flagstone. Rough sand and the fillers I used between flagstones worked fairly well for keeping the joints filled and the pavers from shifting. (Of course aluminum or plastic edging is necessary to keep the edges of each project from shifting outward, but that is another subject). The real downside of these joint-filling materials is that they don't keep weeds down. And yes, there is some washout over time.

Then, a few years ago, I started using a fairly new product: polymeric sand. This type of sand can be purchased pre-mixed for small projects, or added to dry sand and thoroughly mixed for larger projects. Polymeric sand creates flexible, porous joints. The polymer binders in the mixture keep the sand particle continuously adhered one another. Though this product is significantly more expensive than straight sand or stone products like those purchased at sand/gravel pits, there are two major benefits. First, polymeric sand remains where it is placed. There is no washout of this product. Second, polymeric sand creates a barrier to burrowing insects that tend to loosen and expel sand from between joints, and weeds that would otherwise germinate and grow between joints. It is most efficient to use polymeric sand between joints when initially installing a brick or stone paving project. However, it is also possible to replace other joint-filling products with polymeric sand if your product is already in place. "Simply" sweep, blow, scrap, or power wash the sand or stone from between the joints of your pavers. Remove the old sand/ stone. If you have used water to clean out the joints, make sure the pavers have dried completely before putting down polymeric sand. Most of these products tend to stain surrounding pavers if they come in contact water. For this reason, it is necessary to sweep or blow off excess sand before moving on to the next step. Once the final paver compaction is completed, finely mist the entire paved area. This will moisten the top layer of the polymeric sand, thus adhering those grains to each other. Subsequent rain or irrigation will filter down into the joints further joining the particles to each other, ensuring proper adhesion. The joints will look like they have been mortared if they are fairly wide. To the touch, they will even feel mortared. However, scraping or otherwise manually agitating the polymeric sand would loosen it without damage. Once wetted again, the sand will settle back into place and adhere as before. No more weeds or washout.

Warning!  Not all polymeric sands are made equal.  Though I have not used all types, I have kept up on professional forum and have found complaints of hazing from Alliance polymeric sand, excessive splashing from Envirobond polymeric sand which is a very fine powder, and blowouts from Techniseal/Unilock polymeric sand.  I will be doing some investigating and comparisons and talking to other professionals and further fill you in on these issues.  Ultimately, you need to closely follow manufacturers recommendations.  Best practices seem to be to ensure proper compaction of pavers when they are dry; sweep sand into joints; sweep off and blow all excess sand from paver surface; mist the pavers lightly to settle the sand; wait an hour; mist again; wait another hour and mist a final time.

Need some help with project or other paving/hardscape project design, installation or maintenance?
Give Brent a Call @ 616 328-3258.

Fall Projects - Lawn Health

Fall is a great time to improve the health of your lawn. Among the various projects that a home owner can do, or hire a professional to do, are dethatching, over-seeding, fertilizing and weed prevention.

Right now, I am going to recommend dethatching, a simple way to improve the health of your lawn. For those of you who mulch your leaves and grass clippings into your lawn, this is an important step in the care of your lawn. Mulching clippings is a great way to insulate your grass from excessive heat and cold as well as drought that can strain the lawn and open it up to disease and insect damage. Insects love to live in that thatch buildup. Even if you don't use a mulching system on your mower, you should take a look at your lawn to see if build up is occurring. Cut out a small plug of sod in several areas of your lawn. Pull them up a look to see if there is more than half an inch of clippings built up above the soil line. If there is, it is probably time to dethatch. However, years of mulching can create buildup of thatch, which keeps water from penetrating easily. Additionally, for those of you who use insecticides and fertilizers, thatch build up can decrease their effectiveness by blocking the pathway to the root zone. When water, that can not drain properly, comes in contact with these chemicals, runoff occurs. Unnecessary runoff. If you have had trouble with ineffective fertilizer and insecticide applications, this may be your problem.

The goal of dethatching is to remove the thatch which prevents proper water and chemical penetration. Dethatching machines can be rented at most equipment rental stores. I just dethatched several acres of lawn for a client in Grand Rapids. The machine cost $90.00 for a 24 hour rental. I completed the dethatching in about six hours. Not your typical yard. Using a rake, gas powered blower, and a zero turn lawn mower, I removed approximately fifteen yards of old thatch from the lawn. That's seven and a half mounded pickup trucks full. It took me twelve hours to accomplish this.

Most of you won't have such a large project on your hands. One to two hours (maybe) using the dethatcher and another hour of raking would probably do the trick. Rent the machine for under $50.00. Operation of the dethatcher is simple. If you can mow, you can dethatch. For those of you who have a tiny yard, or don't want to spend the money, but have the time, inclination, and strength to do it, you can buy a dethatching rake to do this project.

Once you have finished dethatching your lawn, including raking up the clippings and composting or otherwise disposing of the product, you can move on to overseeding, fertilizing and weed control. Tenacity, one of the newest weed control products out there, can be applied at the same time you are overseeding/seeding and still effectively control post- and pre-emergent weeds according to Syngenta. Check it out: http://www.greencastonline.com/TenacityHerbicide/index.aspx. I'll be testing that product claim this fall and next spring to let you know how it works out.