When you have a new concrete or paver installation put at your home, so much focus is put on the materials that you can see. You likely spend plenty of time choosing the type of stone or concrete that you want, the design of the installation and what it will look like when it’s all complete.
However, if these pavers or concrete aren’t installed properly, that beautiful new installation can quickly turn sour.
Proper installation of driveways all starts below the actual pavers — in what’s known as the subgrade. If you want to prevent your paver driveway from sinking and cracking, you need to have a well-prepared subgrade.
Low-quality subgrades can lead to unexpected water settling on uneven parts of the installation, as well as possible water accumulation against your home’s foundation. This can cause seepage and weakening of the foundation.
If you don’t have a subgrade that’s compacted properly, sidewalks, driveways, patios and other structures are much more susceptible to cracking and sinking.
In all of these cases, homeowners will have to bear the expense of repairs, especially when any settlement in the material causes slabs to move water toward the house.
Below, we’ll discuss the importance of subgrade preparation for driveways in more depth, including how you can ensure proper compaction and drainage.
Compaction and Grading
It may not be obvious, but the quality and the state of the soil beneath a concrete structure plays a huge role in the quality of stability of the structure that sits on it. That’s why it’s so crucial to achieve required density levels for concrete driveways by compacting the soil near the optimum moisture content.
This can be done by using high-powered compacting equipment to ensure that the soil is properly prepared for the concrete that’s going to be poured on top of it. In order to achieve maximum compaction, you must do this before the soil material has dried out too much or before it’s been exposed to periods of rain and wet weather.
Proof rolling, which is also referred to as test rolling, is a practice that can examine a subgrade’s response to heavy loads such as vehicles. This process can be used to identify if the subgrade has been compacted adequately before the layers of pavement are constructed on top of it.
Experienced masonry experts will ensure that the measured density of your subgrade material is between 90% and 95% of what’s known as the Standard Proctor Density, or SPD. In doing so, they will prepare whatever soil type you have to its maximum density based on its moisture content.
Soil Support System
The key to laying a concrete slab that will be stable and last a long time is by providing it with a stable base. The soil support system plays a key role in this.
Native soil that’s already present on the location or even improved soil can be used as a subgrade for concrete slabs. However, both must be compacted to provide adequate support to the concrete that’s going to be laid on top.
If you don’t have enough native soil, or if the soil isn’t adequate enough for a concrete slab, then you or your contractor can use granular fill to provide extra stability. This commonly comes in the form of crushed stone or gravel.
More so than just having this material presented and compacted under your concrete slab, it’s essential that whatever soil support system you use has proper drainage built in and also a uniform bearing capacity. This ensures that no water will settle on the structure and that every inch of the structure is able to handle the weight that will drive on it.
Drainage Considerations
Concrete slabs are not porous, which means that water will not seep through them and into the ground. That’s why it’s crucial to integrate a proper drainage system into your concrete driveway to prevent water from accumulating against the foundation or your home or in other parts of your property.
If necessary, a French drain or other type of drainage system can be installed to direct water away from your house. Whether your concrete driveway needs this — and what type of drainage system would work best — depends on the specific details of your property and where the driveway will be installed.
In addition to installing a specific drainage system, you need to make sure that the subgrade is completely free of all debris and organic materials, which could affect the drainage.
Backfill and Fill Alternatives
There are a number of reasons why you might need to backfill the subgrade with granular material such as crushed stone or gravel. To prevent concrete voids from happening, you need to provide it with a stable base, which will give it strength.
Proper backfilling will help to provide your pavers the base that they need so that an even pour can happen. It’s very important to make sure that when you use backfill that it’s level and has a uniform depth of at least four inches.
In addition to crushed stone, other common backfill alternatives are sand and gravel. These materials can both be used to not only support your concrete slab but also improve drainage.
Concrete Slab Installation
If your concrete slab doesn’t have a subgrade that’s well-prepared and properly installed, it can be very susceptible to sinking and cracking. If there isn’t a stable base, the weight that travels on top of the concrete can actually push the slab down, which makes it sink in spots and crack.
Before concrete is poured onto the ground, you need to make sure that the subgrade is properly graded and compacted. Then, your concrete slab needs to be allowed to cure properly to prevent further damage such as cracking.
Of course, all concrete slabs should be designed and constructed according to the standards set by the American Concrete Institute (ACI). Choosing a local masonry company such as All Brick that has years of experience doing so will help ensure you have a well-designed concrete slab.
Quality Control and Testing
Once your subgrade has been designed and installed, it’s essential that you test it first to ensure that it’s properly prepared and compacted. This quality control process is an important step that shouldn’t be overlooked before the concrete is poured, as it’s much easier to prevent problems than it is to fix them.
Experienced contractors should have processes in place to test the subgrade for moisture content and density before the concrete is placed. After it’s been poured and has cured, they should also test the concrete slab itself for durability and strength.
Even after everything is completed, regular inspections are necessary to prevent damage from happening and ensure longevity.
Final Inspection and Maintenance
One final inspection should be conducted once your concrete slab has been installed. This final check of both the subgrade and the slab itself is essential to make sure that it is safe to use and drive vehicles on.
Like any other part of your house, it’s important to conduct regular inspections and maintenance on your driveway to identify potential issues before they become major problems, which will also ensure longevity.
The subgrade needs to be part of this inspection, as you’ll want to look for any signs of water accumulation or settlement of the material itself.
Finally, the concrete slab should be sealed and protected from the elements.
When you are having a new concrete slab driveway installed, it’s important to choose a local mason you can trust to do the job right the first time. The experts at All Brick have been mastering the art of masonry for the last 10 years and can handle any project you have.For more information, or a free quote, please contact us today.
