Concrete pavers are a versatile, attractive addition to any outdoor residential project. Their ease of installation makes for simple, efficient and timely home set-up with the ability to use the space immediately. To reap the full benefits of your hardscaping for years to come, it’s essential to select and use proper paver foundation materials.
A paver base encompasses several different material layers with varied support functions. The support system under pavers consists of three levels:
- Subgrade: The deepest level, composed of the compacted soil beneath the installation site
- Subbase: The middle support layer applied on top of the subgrade soil
- Base: The topmost material pavers are installed into
When selecting a base, you’re choosing the materials that will anchor your pavers. Each material exhibits properties that either helps or hinders your paver arrangement. For long-lasting, resilient pavers, consider the different types of paver bases to make the best decision for your budget and project.
Types of Paver Base Materials
Your base will determine whether your pavers remain smooth and level or grow uneven with time. Qualities of a suitable base material include:
- Allowance of proper water drainage
- The durability to support the weight and force the pavers will endure
- The appropriate thickness for your subgrade material
Contractors and DIY homeowners use a variety of materials underneath pavers. Here are some things to know about the most common paver bases and their properties.
A sand paver base is one of the most popular options due to sand’s accessibility and spreadability. However, sand is not an ideal base on its own. Over time, sand shifts and can create an uneven foundation. If your foundation is anything but level, your pavers will show it.
Sand is often used in conjunction with crushed stone for increased durability. Because sand comes in many degrees of fineness and coarseness, not all types are suited for use as a paver base. The Interlocking Concrete Pavement Institute recommends washed concrete sand as the best base sand for pavers.
Concrete sand, also known as bedding sand, is coarse and doesn’t trap excess moisture beneath the paver surface. This allows pavers to drain after a heavy rain and maintain their structural integrity over time.
2. Crushed Stone
A crushed stone paver base is made of small stone pieces that have been broken and screened for uniformity. According to the Minerals Education Coalition, common rock types processed into crushed stone include limestone, dolomite, granite and trap rock. Stone aggregate comes in a variety of sizes, but most experts recommend 3/4-inch gravel for paver bases.
Crushed stone makes a solid paver base because it allows water drainage and is easy to work with. Like sand, crushed stone comes in several varieties. The best aggregate for paver bases is a quarry processed dense grade aggregate. Quarry processing creates a combination of 3/4-inch crushed stone and stone dust. This mixture binds well and increases durability, making it one of the best materials for maximum strength and cohesion.
3. Recycled Concrete Aggregate
Recycled concrete aggregate (RCA) is a crushed stone alternative with environmental benefits. Crushed stone is mined as “virgin aggregate” before it is broken into pieces and sold. RCA is made by breaking down existing concrete into gravel. The RCA process has a smaller carbon output and takes less energy than mining virgin aggregate, making it a sustainable option.
Though RCA functions similarly to crushed stone in a paver base, it is impossible to know the different rock mixtures it contains. This unpredictability may make RCA a less reliable base choice when compared to crushed stone. If you’re interested in an RCA paver base, talk to your provider about the quality of their materials to ensure your project runs as smoothly as possible.
4. Stone Dust
Stone dust is a powdery mixture of finely ground stones that has a sand-like texture. Though it can be a helpful base ingredient when mixed with other materials, most professionals recommend that you never use stone dust on its own as a base.
Stone dust and finely ground stone called “screenings” fall into a material category that has excessive amounts of dust particles called fines. The fines trap large quantities of water that prevent the base layer from adequately draining. According to the Interlocking Concrete Pavement Institute, this water storage compromises a base’s ability to bear and distribute loads. To keep your pavers safe and prevent them from shifting, opt for a base material with a little more durability.
5. Compacted Soil
Compacted soil typically serves as the subgrade level underneath pavers. While you could technically lay your pavers directly into compacted dirt, this can cause issues, such as:
- Poor drainage: Compacted soil is not guaranteed to drain well. Prolonged wetness and excessive moisture could cause instability and unevenness in your pavers.
- Initial unevenness: Depending on the location of your pavers, it may be challenging to get a completely even surface with compacted soil alone. Even slight hills and valleys will impact the pavers without a subbase or base level.
- Weather warping: If the soil underneath your pavers freezes in the winter, the ground may sink and buckle as it thaws unevenly. Any transformation in the ground will be reflected in your pavers, creating an unsafe walkway.
For security and evenness, it’s best to install your pavers into other materials on top of compacted soil.
Paver Base Best Practices
Choosing a paver base material is only one aspect of creating a quality base. The way you construct the paver base ultimately impacts its effectiveness and longevity. Perhaps the most practical tip for base construction is to take your time.
Laboring over three base layers before you even begin to lay pavers may seem like a wasteful task. But the amount of time and precision you put into making your base layers the correct thickness, compactness and evenness will pay off. A proper base can keep your pavers beautiful and functional for 20-25 years. If you’re looking for stunning results, base building is not something to be rushed.
With your commitment to detail in mind, the following are some specific base best practices to consider before you install your pavers.
1. Get Started With Excavation
Paver bases require several inches of excavation. Before you start digging, you’ll want to ensure you won’t hit any underground utility equipment. Calling the number 811 will automatically direct you to your state’s call center and allow you to set up an inspection two to three days in advance.
When your utilities are marked, it’s time to dig a base. The purpose of this digging is twofold. It exposes area for the pavers to nestle into, and it clears loose dirt from the installation site. Loose soil is unstable and can’t bear as much weight as hard, compacted earth. Removing this layer provides a strong foundation for your paver base.
For added security, it’s crucial to compact your subgrade soil with a vibrating plate compactor. The more compressed your subgrade soil is, the less it will shift and settle over time. This will help keep your pavers level and in place for longer.
In addition to removing loose soil and compacting the subgrade soil, remove any grass, roots, large rocks or other debris from the paver installation site. This gives you an even surface to layer and build upon.
2. Dig Correct Subgrade Depth and Slope
The depth of your subgrade excavation will depend on the type of soil you have at the paver site. The different soil classifications include:
- Granular soil: Coarse-grained soil composed of gravel, sand or silt that crumbles easily when dry and exhibits very little cohesive strength
- Clay/cohesive soil: Fine-grained soil with high clay content that does not crumble, is difficult to break up when dry and exhibits significant cohesion when wet
Granular soils make strong subgrades that drain well, whereas clay soils are weaker. For that reason, the Interlocking Concrete Pavement Institute recommends a seven-inch subgrade thickness for granular soil and a nine-inch subgrade for clay soil. Be sure to match your soil with your excavation depth to keep your base sturdy.
In addition to depth, you’ll need to incorporate a slight slope gradient in your base for water drainage. With your paver’s location and use in mind, determine which way the subgrade will need to slope to direct water away from the areas you’ll use the most. Your paver site should be sloped 1/4-inch per foot to allow proper runoff. This will prevent water buildup on the pavers themselves and help keep water away from your home.
3. Use Both Sand and Crushed Stone
As detailed above, the best paver base is a quarry processed crushed stone subbase and a washed concrete sand base. Crushed stone’s stability paired with sand’s spreadability makes a manageable, long-lasting base duo.
For best results, use a dense grade stone aggregate and concrete sand that complies with American Society for Testing and Materials standards. ASTM C33 and CSA A23.1 is the recommended sand quality, but ASTM C-144 and CSA 179 graded mason’s sand is also acceptable. Talk to your supplier to make sure your materials align with these standards.
To calculate the amount of sand or crushed stone you should purchase, the Interlocking Concrete Pavement Institute recommends the following guidelines for every 100 square-foot area:
- Four inches thick: two tons of material
- Six inches thick: three tons of material
- Eight inches thick: four tons of material
- Twelve inches thick: six tons of material
Your material providers should be able to assist you with your quantity calculations to ensure you don’t run out during base construction.
4. Compact Your Subbase in Layers
When you begin to build your subbase, you’ll want to scatter thin layers of crushed stone and then compact and slope them. Compacting increases your base’s load-bearing abilities, while sloping maintains the proper water drainage plane.
To compact subbase layers, you’ll need to rent a vibrating plate compactor. These machines look like small, simplified push mowers and are typically manually operated. Their engines vibrate a base plate, which can be used to compress your subbase particles closer together. Vibrating plate compactors come in a variety of sizes, so be sure to rent a machine that makes sense for the size of your paver project.
For maximum effectiveness, complete your compaction one thin layer at a time. Slightly wetting your crushed stone subbase may aid the compaction process. The more tightly-packed your subbase begins, the less likely you’ll experience long-term settling underneath your pavers.
5. Make the Subbase Accurate and Even
Your subbase thickness will depend on the type of subgrade soil you’re covering and the way your pavers will be used. Because it’s weaker, clay soil requires a thicker subbase than granular soil. It is standard to use a four-inch crushed stone subbase over granular soil and a six-inch subbase over clay soil. These thicknesses work well for everyday pedestrian traffic.
If your pavers are located around a pool or will receive vehicle traffic, your subbase should be six to eight inches thick. Extra thickness beyond six to eight inches may help reinforce pavers that will support extremely heavy vehicles like semi-trailers or campers.
To protect your pavers from unevenness, double your subbase thickness in areas that might freeze during the winter. The extra distance between the subgrade soil and the actual pavers will help mitigate any movement due to the ground freezing and thawing.
6. Completely Even the Base
As you lay your concrete sand base, aim to make it less than 1.5 inches thick. Once the sand is laid, you’ll need to level, or screed, it. There are many types of tools to help level the sand base. You can use a flat, heavy 2×4 with an attached handle to smooth out the sand, or you may consider renting a dedicated screed rail for the project. Whatever you decide, the end goal is to have a completely smooth surface for your pavers.
Gently lay the broad side of a 2×4 onto the sand and set a level on it to ensure your surface is as even as possible.
7. Install Pavers Quickly
When you’ve screeded your base, it’s important to install your pavers quickly and carefully. Leaving your base out overnight increases the chances that wind, debris or people will disturb the flat surface. Your base may not be the only structure at stake if you don’t work quickly. Leaving pavers out overnight can increase their moisture content, which may make them susceptible to efflorescence after installation. Efflorescence is the presence of salt deposits on your pavers, which gives them a white or greyish tint.
To avoid efflorescence and keep your base level intact, begin adding pavers directly after screeding.
Find Quality Paving Materials at Nitterhouse Masonry
However you lay the foundation for your project, Nitterhouse Masonry has durable pavers to match. Our paver selection covers a broad range of styles and uses, ensuring you’ll find a versatile and affordable option. As a family-owned and operated business for five generations, we understand longevity. You can trust that our pavers will provide years of aesthetic appeal and convenience after installation.
To learn more about our high-quality products, call us today at (717) 268-4137 or locate a dealer near you.