Laying patio pavers in Denver’s backyards or along a walk is a straightforward affair that doesn’t require much technical sophistication in the way of substrate preparation. However, add supporting the weight of vehicles, such as in a driveway or an RV parking pad, and you have to build a substrate good against more than some frost heaving.
To avoid both heaving and subsidence, you have to start with meticulous foundation preparation. This means excavation, and lots of it. Where a walkway needs a compacted surface supporting about 4-6 inches of compressible gravel, a normal service driveway needs a gravel bed 6-12 inches deep and an RV pad requires at least 18 inches of gravel to deal with the static compression load it will face. Therefore, to have the requisite sand base for the pavers, you may have to excavate nearly two feet of soil to create the proper substrate, and more if your site is facing drainage or water management issues.
Not All Gravel Is Equal
The road beds supporting the asphalt you ride upon daily are not built using clean gravel. It’s a mixture of fine and coarse sand, small pebbles and rocks ranging up to ¾ inch in size. This mix is called 0-3/4 and it is used for the base in roads because this “dirty gravel” is highly compressible. The varied sand grain and pebble sizes allow a matrix to develop between the larger stones, all but permanently locking them into place once compressed.
Compact The Bed And Keep Compacting It
There is no shortcut around thorough compaction of the gravel bed. Trying to compact too thick of a layer of gravel will result in incomplete compaction, so take it slow and compact only a newly spread layer of gravel you know that your machine can thoroughly pound into place.
Remember before laying in the inch or two of screening sand and compacting that, to put in a fabric barrier that will limit the travel of the sand layer into the gravel layer below. If you don’t keep the sand adequately trapped from migrating under load, you will find parts of your paving stone installation eventually sinking under load.
Use A Boundary
A retaining guard around the patio pavers is one last must have detail. You can build the best substrate to stop any part of the installation from sinking, but without a guard, you risk the installation spreading laterally under load, paver by paver. Make sure your bed is wider than your installation to prevent the perimeter stones from tipping out and then place a guard around it.
Come and see the line up of patio pavers in Denver ProCoat Systems stocks, and feel free to ask us technical questions you have about your projects.