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.
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