Masonry Magazine April 2007 Page. 55
PAVERS
Herringbone patterns are recommended for steep slope applications as they resist horizontal forces from automobile braking and turning tires better than other patterns. Dentated pavers may provide additional stability in steep slopes. Other patterns, such as running bond or random patterns, should be avoided.
Paver Installation
The laying of the pavers should begin at the header beam and work up the slope, placed in a herringbone pattern. A 45-degree pattern encourages the surface water to flow to the sides of the pavement, but will likely require more cutting to install. Additional upslope header beams should not be necessary if the pavers are installed from the lowest to highest slope and within stationary curbs. Paver joint widths should be tight-two to three mm - and checked for consistency and alignment every six feet (2 m). Adjustments in joint widths or alignment should be made before compacting the pavers.
The pavement surface should have a minimum 2-percent crown or crossfall to direct water to its sides. A crown can increase interlock as the pavers settle slightly from traffic. The cross slope should allow for sheet drainage of runoff to the sides of the pavement. Flush curbs will allow the water to move off the pavement. Once the water is off the curb, consider how water at the sides of the pavement will be transferred down the slope - it may be sent down a grass swale, a rip-rap lined ditch or a concrete gutter. Regardless of the method, the design objective is to maintain sheet flow and prevent channel flow of water over the concrete pavers.
After a second compaction of the pavers on bedding sand, the finish elevation of the pavers should be 1/4 inch (5-6 mm) higher than the header beam. This will help prevent water from being trapped against the curbs even if there is minor pavement settlement.
Joint Sand Stabilization
A JOINT SAND stabilization material should be placed in all the joints. ICPI Tech Spec 5-"Cleaning, Sealing and Joint Sand Stabilization of Interlocking Concrete Pavement" provides guidance on joint sand stabilizers.
There are two types: liquid applied after the pavers are compacted with joint sand; and those mixed with joint sand and compacted into the joints, then activated with a water spray. Manufacturers' directions should be followed for handling and applying both types of stabilizers.
Stabilizers can reduce the amount of water infiltrating the joints and bedding sand, but they do not render the pavement completely impervious, which is why the design facilitates drainage of the bedding sand. Stabilizers also help to maintain sand in the joints even with exposure to concentrated discharges, such as downspout water, gutter-less eaves dripping water, air conditioning condensation or exterior hose faucets.
Edge Maintenance
THE REPEATED FORCE of tires in the same locations may cause minor settlement over time, as well as minor horizontal creep of the units. This will most likely be evident at the top of the pavement or at protrusions, such as the down slope side of utility covers. If left unchecked, water can enter the opening and undermine the bedding sand. The pavement should be monitored for three to six months for this condition. If joints at the top or at protrusions open a few millimeters, they can be filled with joint sand and stabilized. If wider gaps occur, it may be necessary to relay the pavers to fill the gaps.
These guidelines will require judgment in their application to a specific project and diligent inspection on the job site. Every project will have unique conditions not addressed in this article, and the advice of a design professional experienced in high slope installations should be sought for specific project recommendations.
Reprinted with permission. Copyright © 2006, Interlocking Concrete Pavement Magazine, Interlocking Concrete Pavement Institute
Wide range of paver colors and styles. Meets all ASTM C902 requirements. Extremely durable-strong and colorfast. Size consistent and versatile - often reversible. Clay pavers contribute to LEED certification Low environmental impact for manufacturing and building operation and maintenance. Pine Hall Brick Co., Inc. PO Box 11044 Winston-Salem, NC 27116-1044 800.334.8689 www.americaspremierpavet.com The Voice of the Masonry Industry CIRCLE 309 ON READER SERVICE CARD April 2007 Masonry 53