Flexible Brick Industry Brick Paving Association Pedestrian and Light Traffic Applications Introduction brick pavers are arranged cost savings that upon the bedding sand in supplement the savings the desired pattern. Sand afforded by the brick is then spread into the itself. In addition, spaces between the pavers replacement of pavers as jointing material. after repair of utilities beneath a flexible brick As the whole paving pavement is easily system compacts with time achieved. and use, the bricks interact with the jointing sand and base materials to achieve the unique quality of “interlock.” Interlock holds the pavers in place Brick paving has been used for thousands and distributes the load of years. The Romans laid brick in roads through the layers down crisscrossing their vast empire, some of to the subgrade, enabling which still exist. Americans have employed the surface to contribute the material since the earliest Colonial days, to the strength of the and brick pathways and sidewalks thread whole system. When through the landmark sites and properly installed, brick As an architect’s medium, historic areas across the country. interlocking pavements are brick is equally flexible. highly stable and durable. Its basic aesthetic appeal is legendary as a material Today, as many property the flexible nature of its This basic advantage begets that exudes warmth and owners and architects foundation and the action others. Because flexible elegance through the attest, brick paving is of the pavers themselves. brick paving provides permanent color of fired timeless, especially for In such flexible pavements, interlock, no rigid concrete clay or shale. It can flexible (or mortarless) the subgrade is compacted base is required. Because be installed in such paving such as sidewalks, and covered with a layer no mortar is involved, a popular basic patterns patios, plazas and vehicular of aggregate which itself flexible brick pavement as herringbone, running traffic. One advantage of is compacted. A layer of may be installed with semi- bond, or basketweave, or flexible brick paving lies in bedding sand is added, and skilled labor, producing in creative applications Flexible Brick Paving in Pedestrian and Light Traffic Applications

that employ polychromy, and damaged brick Selection of the most more economical than ornate patterns, and pavers are easily replaced. appropriate material for many other pavement other paving materials. Flexible paving also allows a particular pavement types. The use of some water to filter down requires consideration of sustainable materials Clay pavers in a flexible to the subgrade, thereby a number of factors that such as brick makes an alignment base system are reducing puddles, alleviat- can significantly affect important contribution highly practical as well. ing flooding and runoff, the use, performance to the built environment. They accommodate quick and eventually replenishing and cost of the pavement. Not only is brick an access to underground the water table. Cleaning Although slightly more energy-efficient material utilities, permitting simple usually only requires a to construct initially, the to manufacture, its reconstruction after simple hose-down. And low maintenance aspects contribution to long-term the work is completed. clay pavers provide a safe, of clay pavers in a flexible pavements makes it Without mortar joints slip-resistant surface in base system results in attractive to owners there is less maintenance pedestrian areas. life-cycle costs that are and municipalities.

Basket Weave Basket Weave Herringbone Running Whirling Stack Bond Stack Bond Stack Bond (Variation) (Variation) Bond Bond (Variation) (Variation)

1 Build a solid fou Once a flexible brick Vertical interlock is present Horizontal interlock is In areas sustaining pavement is completed, when a single paver doesn’t most critical in areas where vehicular loads, pavement the system itself goes to settle under load — the traffic may force the pavers pattern is as critical to work to achieve the desired system’s compactness and to shift laterally. Most interlock as the quality of threefold state of interlock. interaction distribute the common in roadways, this materials and installation. Vertical, rotational, and load beyond the single condition known as “creep” Herringbone is known to horizontal interlock occurs paver and down through occurs where horizontal distribute “creep” forces as the pavers settle and layers to the subgrade. braking and accelerating more evenly than running the bedding and jointing With rotational interlock, forces put great stress bond or basketweave and materials interact, aided the paver won’t tilt or on individual pavers. is recommended for by the rigidity of the rotate on its horizontal Horizontal interlock trans- vehicular areas. edge restraints. axes when force is applied fers these forces through to an edge, but will always the joints and pavers to the remain flat. rigid edge restraints.

Components of Flexible Brick

2 ndation

Mortarless Brick Sand Base Max 2” (50mm) Compacted Sand Base Flexible Brick Paving in Pedestrian and Light Traffic Applications

Geotextile Compacted Earth

Concrete Base Mortarless Brick Max 1/2” (13mm) Sand Setting Bed Min. 4” (100mm) Concrete Base

Compacted Sub-Base

Compacted Earth

Asphalt Base Tack Coat 2% Neoprene 3/4” (19mm) Mortarless Brick Modified Asphalt Adhesive Bituminous Setting Bed

Min 4” (100mm) Concrete Base

Compacted Sub-Base Paving Compacted Earth

3 Design Opportun

Designs for flexible brick pavements are as fountains. Round-edged to heavy vehicular areas. varied as their uses: from basic colors and and chamfered pavers In any application, it is patterns, to other, newer applications. produce bolder lines, critical that the ground Whether employed in Colonial or contempo- enhancing many and grade be analyzed rary projects consisting of buildings and bond patterns. carefully, that the founda- pavements, brick has proved itself a medium tion be planned properly, that’s kept pace with the latest design trends. Brick paving systems that the correct base, cover the full breadth materials and pavers be Apart from some specific Brick paving sections can of pavement uses, from specified, and that the traffic considerations that alternate patterns or colors, pedestrian applications installation be carried will be discussed later, the may be used with other out correctly. choice of standard bond paving materials to achieve patterns generally follows interesting effects, and taste. Running bond, to delineate such specific basketweave, herringbone, areas as plazas and paths. stack bond, and variations One popular variation Interlock on all these patterns exploit combines running bond brick’s modularity and the with stacked bond placed aura of tradition. around planting beds and

No Vertical Interlock

Displaced Sand Displaced Sand

Vertical Interlock

4 ities

Deciding on the appropriate brick paving system to use is important to ensure prop-

er performance. Since brick Flexible Brick Paving in Pedestrian and Light Traffic Applications can be used in a variety of ways, the following is a guide to help you decide on what works.

Interlock, the key to a stable flexible brick pavement, is formed by the interaction of pavers, base and bedding materials, and jointing sand. As these diagrams illustrate, interlock distributes vertical and rotational loads down to the subgrade and shifts horizontal forces out to rigid edge restraints.

No Horizontal Interlock No Rotational Interlock

Horizontal Displacement Horizontal Displacement

Horizontal Interlock

Rotational Interlock

5 Many of the variables vehicular traffic require to be considered in the design by an engineer. design of a flexible pave- (See BIA Design Guide for ment are site dependent. Vehicular Pavements.) Optimally, the subgrade Considerations should also will be free of tree roots address the potential for or rocks (they should be frost heave, which can removed, and holes filled leave permanent changes with appropriate backfill). in the soil and therefore Proper drainage is essential the paving surface. The in all pavements. Adequate base, like the subgrade, slope should be included should achieve a 95% in the design to avoid compaction rating. standing water (a minimum alignment slope of 1/4 inch A rigid edge restraint is per foot is recommended, required to secure the with a maximum grade of whole paving system 10 percent). Larger paved laterally. Since it extends areas may require down below the level of the intermediate drains or bedding course, the edge scuppers. In areas with a also serves to hold that high water table or with crucial layer in place. soils with high moisture Concrete, stone, metal, retention, sub-surface some types of plastic or a drainage systems and/or soldier course of brick set geotextile layers should be in concrete can serve as an planned. Curbs and plant- edge restraint. The border ing beds are often higher can be planned to comple- than the paving surface so ment the design of the drainage at these elements pavement and also to pro- must be considered or a vide a channel for surface “bathtub” effect may occur. runoff. Special shaped bricks can be used to create The thickness of the entire elegant curbing for your paving system should be paving project while also calculated according to acting as an edge restraint. its traffic load. Generally, a minimum base thickness Trees are an important of 4 inches is required for part of any landscape plan. all areas and 6-8 inches Trees in urban areas are for light vehicular areas. more prone to failure Medium and heavy because of soil compaction and lack of water and air.

6 To avoid this, the use of a structural soil and permeable surface are required. Structural soil usually contains about 80 percent crushed gravel or lightweight aggregates by weight. The nature of flexible brick paving allows water and air to get to the roots. Pavers with slightly wider joints may be used

around the tree. Flexible Brick Paving in Pedestrian and Light Traffic Applications

Expansion joints are usually not necessary in flexible brick pavements. The sand joints allow for most expansion to occur without distress. Expansion joints are still a good idea for permanent structures that come from below the base, such as bollards or manholes. Expansion joints are necessary in walls and mortared brick paving since the expansion of the brick can cause cracking.

One item that is often overlooked is a mock-up of the pavement. A mock-up should be built to illustrate just how the paving will look with samples of the actual pavers and bedding materials. This can also serve as a standard for workmanship. All bond patterns should be inspected closely before work begins.

7 Specifying the P medium traffic volumes. resistance, especially if Pavers in applications they have a wirecut receiving high volumes texture. Obviously the of heavy vehicles (tractor- rougher the paver, trailer trucks) should be the more slip resistant. specified using ASTM C 1272 and are covered in Paving bricks, used flat another publication. or on edge, should be (See BIA Design Guide for specified according to Vehicular Pavements.) the desired pattern. For maximum design flexibility, The thickness of the it is recommended that the pavers will vary with the brick be twice as long as application. The suggested it is wide. Pavers can be minimum thickness for specified with rounded flexible brick paving is: or beveled edges called light pedestrian traffic — chamfers. These chamfers In addition to correct planning, a successful 1 1/2 inch; for medium and emphasize bond patterns, flexible brick pavement depends on the heavy pedestrian or light limit the height variation right materials, both in its wearing surface vehicular traffic — 2 1/4 between pavers, and reduce and in its foundation. inch; and heavy vehicular standing water, which in traffic — 2 5/8 inch. turn assists in drainage and Thicker pavers are required reduces slippery pavements. For outdoor brick pavement withstand repeated freeze/ in heavy-duty applications In areas where snow designed for pedestrian and thaw cycles and exposure to help resist traffic removal must be consid- light traffic, the pavers to salt without damage. loads as well as develop ered, the chamfers help should be in accordance interlock. prevent chippage due to with ASTM C 902, Class SX. A paver conforming to shoveling. Many brick shapes, colors, ASTM C 902, Class SX is Since safety of a brick and sizes are available with “intended for use where the pavement is critical, the A flexible brick pavement is this rating, and the classifi- brick may be frozen while slip resistance of paving only as good as the base cation signifies the paver’s saturated with water” and units should be examined. beneath it. To ensure a strength and ability to may be specified for walk- Skid resistance in vehicular smooth surface over time, a withstand weathering ways, patios, pedestrian areas is also important. base layer of 3/4-inch or elements. This assures plazas and driveways Most brick pavers have smaller aggregate should be the specifier that it can subjected to low and adequate slip and skid laid over the compacted

8 roper Materials earth. A crushed stone, when accepting stone bedding course. Mason’s also called crusher run or screenings as a substitute, sand meeting ASTM C 144 road base (ASTM D 2940), particularly in vehicular is the standard. Bedding provides sufficient areas. Screenings may sand can be used for Flexible Brick Paving in Pedestrian and Light Traffic Applications strength. Heavier loads not be graded appropriately jointing sand as a matter and more severe frost or may be too soft — of convenience although conditions on the pavement compromising interlock. some larger pieces may require thicker bases. In addition, screenings may remain on the surface contain sodium, lime or after sanding. can be placed below the For the bedding course, calcium that produce base thereby positively which is laid over the base, efflorescence. The jointing In some instances, a separating the layers washed sand no larger than sand, which will be spread membrane such as a and reinforcing the base 3/16 of an inch should be over the brick pavers and geotextile may be used slightly. A geotextile used (ASTM C 33 Concrete into the spaces between to strengthen the system should be used since other Aggregate is acceptable). them, should be smaller by keeping the layers plastic membranes do not Caution should be used than that used in the separated. A geotextile allow water percolation.

Table 1 Physical Requirements Designation Average Compressive Average Cold Water Saturation Coefficient, max Strength, min, (ps) Absorption, max, (1%) Class SX 8,000 8 0.78 Class MX 3,000 14 no limit Class NX 3,000 no limit no limit Physical durability requirements are denoted by “Class” as follows: Class SX is Brick intended for use in freezing conditions; Class MX is brick used where resistance to freezing is not a factor; Class NX is brick used for interior applications Table 2 Abrasion Requirements (1) Abrasion Index, max (2) Volume Abrasion Loss, max, cm3/cm2 Type I 0.11 1.7 Type II 0.25 2.7 Type III 0.50 4.0 “Type” describes traffic demands. Type I denotes brick exposed to extensive traffic; Type II represents intermediate traffic; Type III signfies low traffic. Table 3 Tolerances on Dimensions Dimensions, in. Maximum Permissible Variation from Specified Dimension, plus or minus, in. Application PS Application PX Application PA 3 and under 1/8 1/16 no limit Over 3 to 4 3/16 3/32 no limit Over 5 to 8 1/4 1/8 no limit Over 8 5/16 7/32 no limit Application: describes use. Application PS represents general use (usually with a mortar joint); Application PX denotes use in a mortarless system or with a special bond pattern; Application PA signifies special architectural effect. 9 Pavement Instal The ground must be Bedding course sand is compacted and stabilized then spread over the base for both strength and materials. It is smoothed drainage. The base should over with a board known also be well compacted to as a “screed board,” which avoid filtering-down of the runs along pipes placed bedding sand. Rammers, on the base or the edge vibratory plates, or rollers restraints. This layer may be used, depending on should follow the intended the compaction needed — grade of the final wearing 95 percent maximum surface. density is recommended. Pavers may now be placed Base materials should in the desired pattern. be laid in consistent, well A space of 1/16 of an inch packed layers (4 inches to 1/8 of an inch should be max) that build up to a left between pavers. Care surface that will match the should be taken by the intended elevation. Rigid installer to ensure some edge restraints are usually space is left between the installed next, and if pavers as the tendency is Once planning has been completed and the they consist of or include to lay them too tight caus- appropriate materials obtained, a flexible concrete, they should be ing poor interlock or paver brick pavement can be installed relatively cured before pavers are chippage. Laying tech- quickly. Because there is no mortar involved, laid. One or two sides niques vary with specific brick pavement doesn’t require the skilled should be left unedged, patterns. A 45-degree her- labor of masons, doesn’t need to be complet- with a board set as a ringbone should start at a ed at one time, and requires no curing. temporary form. The corner or the centerline. final edge restraints will When using a running be set in place after the bond pattern, the pavers’ On site, brick pavers should with weighted plastic to brick are installed, so long edges should be be stored off the ground. maintain dryness and wind that less brick cutting placed perpendicular to the Base and bedding course protection. Installation is required for final flow of traffic. Whole materials should be stored during rain or snowfall adjustments. pavers should be placed separately and covered should be avoided.

10 llation first and then pieces cut collars to avoid awkward process of interlock. To Sanding and compaction cleanly to size. Alignment cuts, or use a perimeter avoid shifting or breaking, takes place again until should be checked from stacked bond border to the compactor plate should the joints are full. time to time during the move cuts away from the be at least two feet square Flexible Brick Paving in Pedestrian and Light Traffic Applications process, so that simple edges. Sailor borders are and produce 3,000 to 5,000 The brick pavement adjustments (either shift- also used at the pavement pounds of centrifugal force. should be planned to lie ing the size of gaps or borders to “frame” the The compactor should have flush with any adjacent redoing single paver rows) pavement and to bring a rubber pad to avoid dam- pavement, and pavers can be made to assure a cuts away from the aging the pavers. After the abutting drains or gutters clean, consistent bond pavement edge. initial pass of the plate should be calculated to lie pattern throughout. compactor, jointing sand is no more than 3/16 of an Obstacles, such as manhole A plate vibrator should be then spread into the spaces inch above the level of or water covers, should used to compact the pavers between the pavers. these drainage systems. be prepared with square into place and initiate the

11 Maintenance an Coatings should not be applied in most climates, Brick pavements are easy to maintain. as they could trap moisture Cleanup usually requires only a or salts that could damage simple hosing down. the brick or make stains more difficult to remove. Evaporation of subsurface water may cause the coating to become cloudy. And in some areas, a joint When a sand stabilizer may be cleaner is necessary to keep the deemed sand in the joints, helping necessary, to keep system interlock. acid solutions Products especially made should be avoided. for this situation should Light brushing with plain Snow and ice can be be used rather than water will remove most removed with normal hand all-purpose sealers. surface dirt. A commercial equipment or motorized cleaner or a 50-50 solution vehicles. Rotary brushes of bleach and water will and snow blowers are remove most moss or algae preferred. Snowplow growth. In addition, time blades should be equipped and weather will eliminate with a rubber edge and set most efflorescence. 1/4 inch above the pave- ment. The use of rock salt is not recommended since it will cause efflorescence. Non-sodium de-icers that are environmentally compatible are available and the use of sand or cinders will provide some traction.

12 d Cleaning Flexible Brick Paving in Pedestrian and Light Traffic Applications

13 Summary Brick manufacturers Offering a variety of For more information continue to expand pave- styles, structural stability, regarding brick paving ment design possibilities. and economic value, systems or any other Many paver sizes and colors flexible brick pavements are brick applications, the are available, as are special anything but pedestrian. Brick Industry Association Brick Industry Association shapes such as squares and Ingenuity, proper planning can provide the architect hexagons. Some pavement and careful installation will or contractor with a wide 11490 Commerce Park Drive systems come designed almost always assure their variety of detailed Reston, VA 20191 in ornate patterns that success. publications. These (703) 620-0010 integrate component include a Design Guide for (703) 620-3928 fax pavers of different Vehicular Pavements and e-mail: [email protected] colors and shapes. the Technical Notes 14 website: www.brickinfo.org Series on Brick Floors and Pavements.