Interlocking concrete pavers are an excellent option for their versatility and design options for patios, walkways, or driveways. If they sink, they can be easily fixed. Whereas other pavement options will show signs of settling through cracks on the surface. There are aspects of the paver installation that can help prevent pavers from sinking including the basics of base material, excavation depth, and compaction. There are also other products that can be used within your base to help stabilize the project including geotextiles and geogrids.
How to Stop Pavers from Sinking
If your pavers are already sinking, they can be fixed. You can learn more about fixing sinking or uneven pavers here. However, if you want to prevent your pavers from sinking in the future, we will walk through the most important things that will cause pavers to sink and what you can do to prevent that from happening to your project.
Base Material for Pavers
A long lasting paver project starts with the right base material at an appropriate depth for your climate. Depending on your project, there are several different base preparation methods that you can install. These include a dense graded base which is traditionally used and includes 3/4″ angular crushed stone down to fines as the base material with concrete sand as a 1″ bedding layer which the pavers are laid on. Open graded base is becoming increasingly popular thanks to its permeability and includes a 3/4″ angular crushed clear stone with no fines along with a 1/4″ angular crushed clear stone or HPB as the 1″ bedding layer. Alternative to these two is a synthetic base which is comprised of a one inch bedding layer of HPB with paver base panels laid on top which the pavers are then laid upon. These panels insulate the ground while spreading the load out over a wider area allowing for minimal excavation compared to the other two base preparation methods. Regardless of what base preparation method you choose, you need to ensure that the organic materials are removed so that you begin building your base on foundational soil such as sandy, silt, clay, or a combination of these.
One base material that should never be used is stone dust. It soaks up and holds onto water which causes heaving and sinking of pavers. It does not do a great job of allowing water to permeate through it like these other base materials do. Stone dust is comprised of 1/4″ chip down to fines and is the waste material that quarries create when creating other aggregates and is usually the cheapest option that provides the cheapest result.
The other thing to consider with your base is the depth. This is going to depend on the climate and traffic. For pedestrian applications in a cold climate, you are likely going to need to excavate for a 6″ base for pedestrian applications and 12″ for vehicular applications. T calculate your entire excavation depth for pavers you would also need to include the depth of your bedding layer and height of your pavers. You will also want to excavate past your pavers (the length and width of your project) the same depth of your base. So if your base is 6″ you would excavate past your pavers 6″. These allows for a stable platform for your pavers to rest on and leaves room for the edge restraint.
Compacting Base Material for Pavers
Compaction is the most important aspect of keeping your pavers from sinking. Failure to compact properly will cause the base to settle over time which is most common within the first few feet along a foundation as this material was excavated during the preparation of the house foundation and backfilled (sometimes without compaction).
Compaction begins with the subsoil with an appropriate ramming compactor for cohesive soils. The ramming action is important for cohesive soils. You can use a jumping jack compactor or a large reversible plate compactor for this. With the remainder of the base you can use a plate compactor. The rule of thumb for compacting is for every 1,000 pounds of force that the compactor can apply would equate to 1″ of gravel lift. So if your plate compactor is rated for 3,000 pounds, then you should not compact more than 3″ of base material at once.
Open graded base is a lot more forgiving and requires less compaction than a dense graded base. Dense graded base requires moisture when compacting to ensure proper compaction. You will need to wet the base, but not to the point of pooling water prior to compaction.
Geotextile for Paver Base
Geotextiles provide numerous benefits to your paver project. The separate the subsoil from the base material ensuring there is no contamination between the two. Non-woven geotextile will also promote drainage, whereas woven geotextile will reinforce the base material that is placed on top of it. This reinforcement can ensure that if you subsoil settles slightly, that settlement will not transfer up to the surface. It will help to bridge over that settlement and therefore reinforce the base from following that same settlement.
Geogrid for Paver Base
If you prefer to use a non-woven geotextile for its drainage features, or to add additional stabilization along with woven geotextile, you can use biaxial (strength in two directions) or triaxial (strength in three directions) geogrid. These geogrids have apertures or openings that interlock aggregates and help to stabilize material placed on top of it. This is an inexpensive option to be able to provide a stable pavement with your interlock installations especially for projects that experience heavy traffic loads.