Why we recommend stabilization grids no matter the scale of your paver project.
Yes, even for the backyard pool deck or patio pavers
The need for stabilization grids is something that is largely unrecognized throughout the construction industry which sort of boggles the mind. I would say that the large-scale industrial masonry world is understood because they have heavy-duty architects working on road projects, etc. those that require forethought, and longevity. Unfortunately, on the mid-size to small scale projects ie: from parking lots to a backyard patio or pool paver projects, it’s usually not a consideration for reasons that are not understood by me.
Stabilization is at the heart of the project when it comes down to longevity of the installation. Anybody can lay down some stone or pavers on soil or grass or anything and they’ll stay there for a week, a month or a year, but if you want them to stay in place for 10, 20, 50 years, you need to have a stable substrate. As with tile and exterior pavers, it’s all about the substrate. Without the proper substrate, nothing else matters because you will have failure – 100% guaranteed.
So, with that being said, without the soil stabilization under a paver installation, you’re extremely likely, in almost every scenario, to have some movement and there are some very stable environmental situations that may not necessitate it particularly, climates that don’t have much temperature change, climates that don’t have a lot of rain, and have very compacted sandy soil, so, you will not get a lot of movement underneath. But you know that is a very small portion of the world we live in that has that kind of climate. So, conversely, if you have a lot of rain, if you have a lot of temperature change, particularly if you have a lot of cycling in freeze/thaw, and that’s the real killer, you’re going to have movement in your substrate. When you have movement in your substrate, you’re going to have movement above your substrate, just by definition, that’s what’s holding your stone, the substrate. So, by definition, if the substrate moves what it’s holding, is going to move. And, that’s the need for soil stabilization grids.
When you have a concrete slab, it’s the old-adage, it’s not IF your slab will crack or fail, it’s WHEN. Concrete slabs are extremely prone to failure because it’s asked to perform very unforgiving and next to impossible task, and that is to endure movement underneath them without cracking or failing. And, again, when you have movement underneath, you’re going to have cracking and failing. Even the concrete itself is prone to failure without movement from underneath because of the heat, especially in very hot climates, and or cold or thermally cycling climates, where it gets cold then hot, cold then hot, because the slabs will expand and contract according to how much heat they are exposed to and how much cold they are exposed to and particularly, the cycling heat cold, heat cold. So, small concrete slabs, for sidewalk sections 3’x3’ or 4’x4’ not a big concern. Unfortunately, enough people do not put expansion joints even there, they put control joints, which when it fails, it fails along the control joint. A control joint is nothing more than a little line cut into the surface of the concrete making it a little bit weaker on that line so if it cracks, the crack goes along that line that was cut into it. So, it’s a prettier failure. The concrete slab is not the best solution.
The use of the grid, if you don’t have elevation problems and you want a new surface, I would put, if you have elevation problems, put a membrane down, a very thick and hefty membrane then wet-set your stone. If no elevation problems or choose to raise your elevation, it’s perfect to put a grid down on top of existing concrete slab and, put pavers on top of that.
Benefits of using STABILIZATION GRIDS:
What happens when there is failure ie: wash out from too much rain underneath, and without a properly compacted substrate, you can have the substrate washing out from flooding, heavy floods, constant flow of water eventually eroding underneath, the stabilization grid will hold that substrate together so that it’s not possible to wash out. The gravel can’t go through the walls of the grid so, it holds it in place. One of the bigger dangers is the freeze/thaw expansion and contraction issue that is extremely common in the climates of the upper 48 states in America and that is a common thing around the world. When you have snow and cold weather, warm weather, then cold weather, warm weather and moisture cycling. What happens is that moisture gets underneath the pavers and freezes. And, as we all know, when you look at ice cubes, in your freezer, they all have a hump in them because when water freezes, it expands, why the hump in the ice cubes. So, you’re going to get the substrate having water then if there is quick freezing overnight, the water will expand and therefore, your whole installation will heave up a little bit. When it heaves down, when you use the grids, the grids will hold it in place instead of it shifting a little bit every time. When it shifts a little bit every time, from heaving then relaxing, heaving then relaxing, heaving then relaxing, you can imagine things will start to spread out over many cycles and next thing you know your pavers are 1/8” apart then ¼” apart, next thing you know, now they have those openings and more water attacking it and now you have bigger gaps for the water to go in and turn to ice and more wash out issues, etc. The whole thing kind of goes to hell.
Further technical information, go to http://celltekdirect.com/lsg.html