Stick to the basics: sell and install the system

When it comes to interlocking pavements we tend to forget that the successful foundational properties of this type of pavement have been around for thousands of years. It’s easy to be misled by those who make up new ways to install pavers, but who lack the basic understanding of how an interlocking pavement system works. If you understand the fundamentals and stick to the basics you will always be assured of building a good project.

An interlocking pavement is categorized as a flexible pavement and typically incorporates the same basic design characteristics as asphalt pavements. When I talk with someone who doesn’t understand the “system,” I mention that a paver system is similar to an asphalt system.The design criteria and road base construction methods are very similar to the design and installation typically used with asphalt pavements. Though most people don’t understand the assembly underneath asphalt, they do recognize that asphalt is used in all types of applications successfully, and this helps give them a level of security and trust that a paver system with similar base design should perform as well if not better than asphalt.

A quick tip for setting the road base thickness on a project is to ask for the Soils Report. That report will give engineered recommendations for the road base thickness used under asphalt in your area.

Here’s a rule of thumb I use: If you replace 4” of asphalt with a 1” sand bed and a 3” paver, in most cases the base design for the asphalt should work for the pavers on that particular project. If one isn’t available install a minimum of 6” of road base for driveways and 4” for patios and walks.What is a good road base material? Google what your local D.O.T. uses under their asphalt pavements. That is what you should use. Don’t get persuaded into using byproduct materials etc. If your local D.O.T. won’t use it, you shouldn’t either.

Some people think the term “interlocking pavers” has something to do with the shape of the paver. It doesn’t. Interlock is the relationship of pavers working in conjunction with the sand in the joints to help spread loads that are applied to the surface of those paving stones. Interlock happens once the pavers are compacted with a plate compactor into the sand setting bed. This is the reason that the type of sand and the size of the paver are so important for the success and durability of a segmental pavement.This is also the reason that “polymeric type sands” are not typically used in vehicular applications. The type of sand and the gradation of sand is a key factor to the long-term success of a project. In fact, it is so important that there is even an ICPI Tech Spec dedicated to this subject, Tech Spec 17.The majority of sand used for both the bedding sand and jointing sand should be an ASTM C-33 sand or “concrete sand.” There are many suppliers of hardscape products that don’t sell this type of sand. Do not settle for any other type of sand that doesn’t meet the gradations of C-33 sand. C-33 sand is what is used in the production of standard poured-in-place concrete.

The sand setting bed should be 1” thick. We don’t want to try and create our slopes by increasing the thickness of the sand setting bed. If we need to create slopes, this needs to be done at the road base level. The road base surface should be a mirror image of the final grade of the pavers.

By sticking to the basics for base, sand and pavers, and designing/constructing your jobs to ensure interlock, your projects will share the success of the paver system that has worked for thousands of years.

‍Frank Gandora CCPI, CS, PICPS is President of Creative Hardscape Company in Lakewood, CO. Frank is also a certified hardscape trainer and a regular seminar presenter at Hardscape North America.