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There are a few different ways in which we prepare our paver bases depending on the application. Choosing the best base for pavers depends entirely on the application. Driveways, front entrances, patios on the existing grade, and raised patios all have varying base materials. However, there are only a few different aggregates that are used in these installations. In this article, we are going to highlight these different materials and their uses in the hardscape industry.
Gravel Base for Pavers
There are four different aggregates that are used in the installation of a paver base. Using the proper gravel under pavers is important to the quality of the end product and the longevity. Along with that, the proper compaction of this gravel is incredibly important for the same results. One thing these aggregates mostly have in common is that their larger granules in the aggregate are angular in shape to allow for the lockup of these granules in the base material to prevent movement.
There are two different installation methods with these four aggregates. One is a traditional method using a dense-graded aggregate and the other is an open graded method using an open-graded aggregate. Learn more about both of these methods and the aggregates used in them below.
- Traditional Install
A traditional paver base consists of a granular material with fines that allow for the cohesivity. It is the base that is recommended by the Interlocking Concrete Pavement Institute for installers to follow.
- Granular A Gravel / ASTM D2940
- Concrete Sand / ASTM C33
This is a sand and crushed gravel or rock mixture. It is sometimes referred to as Granular A, A Gravel, or 3/4 minus. It is the traditional material that is used in the construction of pavement surfaces or the base for retaining walls. It is a dense graded aggregate that is compacted in lifts according to the capability of the compactor in order to reach a minimum 98% Proctor density.
This sand is the specified sand for a maximum of 1″ bedding layer on top of the Granular A material in order to screed and provide a level surface for your pavers to be laid on top. It is a small coarse granule that is made from the crushing or natural disintegration of stone. It is a coarser grain than masonry sand in order to provide proper drainage of any water that enters the system.
Open graded bases hold several benefits over a traditional base installation, as long as proper drainage is accounted for in the system. The aggregates used in this installation are clean or clear stones. This means that they are free of fine material in them, ensuring the water drains through them with minimal resistance. The granules are angular in shape in order to be oriented and locked together ensuring proper compaction of the material.
- 3/4 Inch Crushed Stone / ASTM 57
- High Performance Bedding / ASTM 8 or 9
This is an angular crushed clear stone that is free draining, allowing water to flow through it with minimal resistance. Typically used in drainage applications such as around drain tile in French drains or in backfill behind retaining walls, it is also used in open graded base installations under pavers as the base as long as proper drainage is accounted for. It does reach high compaction ratings without mechanical compaction, but will settle after mechanical compaction re-orients the aggregate.
In an open graded base installation, HPB is used as the bedding layer of a maximum of 1″. This is an angular crushed clear stone with a maximum nominal size of 1/4″. It does reach up to 90% compaction without mechanical compaction which does make it a useful aggregate when levelling pavers. This particular aggregate is used in an open graded base as the bedding layer as an alternative to a concrete sand because the sand would migrate into the 3/4″ crushed base, whereas HPB will not (though some installers will opt to lay down some non-woven geotextile on top of the base material before screeding HPB on top to prevent any minimal migration).
How Much Paver Base Do I Need
In climates that experience freeze-thaw cycles, the depth of a patio base would be 6 to 8 inches and the depth of a driveway base could be as much as 12 inches in depth on more cohesive soils. These are the depths that we prepare our gravel bases in our climate and on the clay soils that we typically run into, but this is approximately 2″ more than what the Interlocking Concrete Pavement Institute recommends.
Best Paver Base
The best gravel for a paver base depends entirely on the application. As long as you opt for any of the above noted installation methods or with a synthetic base installation which will use paver base panels and follow the proper installation of interlocking pavement, your project will stand the test of time. The major factor for any paver failure is either improper compaction or drainage. You can learn more about these aggregates and the base preparation methods by using the links above.
Paver Base Calculator
Knowing how much paver base that your project will need requires that you have three measurements from your project. You need the length in feet, the width in feet, and the depth in inches that your gravel will fill. Using these measurements, you can complete the formula below to calculate the amount of gravel that you will need in cubic yards.
[Length (in feet) x Width (in feet) x Depth (in inches)] x 0.003 = Total Cubic Yards