Line Streets, Sidewalks, And Beyond
By Ted Corvey
Photos Courtesy Of Pine Hall Brick Company
Stroll through downtowns, city parks, college campuses, and backyards to see the oldest trend return: genuine clay brick pavers used in sidewalks, streets, driveways, and patios. Because the pavers are the same color throughout, they combine classic aesthetic appeal with today’s emphasis on “green” construction. Durable enough to last centuries and made from clay and water—two of the most abundant building materials on the planet—these pavers are the essence of sustainability.
Some of the newest clay pavers are “green” twice:
- They direct stormwater into the ground instead of allowing it to wash across the surface and carry pollutants to the nearest stream.
- Except for tiny bits of gravel rather than sand in the joints, modern pavers appear indistinguishable.
Any new brick installation requires research, beginning with the materials. Traditional 4-inch by 8-inch pavers are made with square or beveled edges, while tumbled pavers are tumbled in steel drums after firing to make them look older. New pavers that appear antiquated are less expensive than reclaimed brick, are more durable, and are of consistent size, which makes installation easier. Veneer or face bricks being sold as pavers are not intended for contact with the ground, and may not last as long under the pounding of vehicular and pedestrian traffic.
Once material has been determined, it is time to consider the desired size and pattern for the project. Square and rectangular designs are viewed as more formal, while curved installations are more casual. Some patterns will require more cuts than others. There are several methods for installing clay brick pavers, including conventional flexible base, a permeable system, and installation over existing concrete.
Conventional installations require:
- Crusher run gravel
- Edge restraints
- A compacting machine or hand-held tamper
- A broom.
As a general rule, conventional pavers require about 4 inches of compacted, crushed stone as a base and upwards of 8 inches in harsher climates where ice heaving is a problem.
For use in trafficked areas—such as a driveway—a base between 8 inches and 12 inches is recommended. In roadways, it is advised that an engineering study be conducted. A good rule is to inquire about the generally accepted practices and use them.
Dig deep enough to include the depth of the crusher run gravel, 1 inch of sand on top of that, and the paver itself, which should be flush with the surface of the ground. Dig 6 inches beyond the area to be paved. Slope the soil about ¼ of an inch per foot to allow for proper drainage. Next, tamp the soil down with the tamper or plate compactor.
Put the crusher run gravel down and compact it well. Next, lay down two lengths of 1-inch outside-diameter pipes (metal or PVC) parallel to each other and several feet apart. Cover the pipes with concrete sand, and then use a board across the top to screed the sand level. Remove the pipes and use a trowel to fill and smooth voids. Lay the pavers in place, leaving a joint at least 1/16-inch wide between. Then, install edge restraints, which can be metal or plastic, or even stand a row of finished pavers on end or use troweled concrete. Tamp or compact the pavers into the sand bed. Always use a cushioning device to avoid chippage. A neoprene mat may be available for the compactor, or use a piece of scrap plywood or carpet on top of the pavers. After that, sweep sand into the joints.
A permeable-paver system is somewhat similar, except that special open-graded aggregates without fine particles are used instead of crusher run and sand. In addition, special permeable pavers with larger nibs—spacers that keep the pavers apart and allow water to seep between them—are required.
Figuring the depth of the underlayment is also different. The standard is to dig down 12 inches, but some installations, as in streets, are much deeper. Since the idea is to trap stormwater and then release it slowly into the ground underneath, the depth depends on how much water needs to be handled, which is a question for an engineer.
Use #2 stone as a sub-base, followed by a finer grade of #57 stone. The bedding layer, just beneath the pavers, is #8 or #89 aggregate, which is also swept into the joints. Every 4 inches, roll or compact the aggregate into place. The series of aggregates allow water to flow as bacteria builds around the rock over time and aids in reducing pollutants.
The installation may be challenging, but the rewards are two-fold. Permeable pavers allow builders to potentially qualify for LEED credits in four ways, including stormwater design, heat island effect (non-roof), use of recycled content, and use of regional materials. In addition, when the cost of maintenance is included, permeable pavers may actually cost less than asphalt.
Existing Concrete Installation
To install brick pavers over concrete, start by choosing the type of clay paver and a pattern. Some pavers—1 3/8-inch thick—are especially made for this purpose.
To begin, lay a “soldier course,” a line of bricks perpendicular to the edge of the concrete to form the outside frame of the project. The secret is to use four or five dots of masonry adhesive on each brick, each about the size of a penny, which allows rainwater to pass underneath.
It helps to set two borders first, lay the pavers, and then set the remaining two. It also helps to measure the pavers in the pattern first as the edge course can be adjusted slightly over the edge of the concrete in order to limit cuts to half pavers or eliminate cuts altogether.
On the inside of the soldier course, cut pieces of roofing felt to put a single layer inside the frame covering the concrete, and don’t overlap the felt edges. Then lay a second layer of felt perpendicularly over the top of the first layer.
Starting at one corner, begin laying the brick in place, leaving a 1/8-inch gap between the pavers. Finish by sweeping concrete sand between the joints until they are full.
There may be a construction program at a trade school nearby, or you can take advantage of apprenticeship programs offered by trade associations. Examples include the School For Advanced Segmental Training ( www.paverschool.com) and the Interlocking Concrete Pavement Institute. Training is also offered at the Hardscape North America trade show ( www.hardscapena.com ).
Ted Corvey is a recognized national authority on clay brick pavers and their installation. Corvey is the vice president of sales and marketing at Pine Hall Brick Company, a manufacturer of clay brick pavers. For more information, visit www.pinehallbrick.com or call (800) 334-8689.