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Technical Notes 14
Brick Floors and Pavements,Part 1 - Design and Detailing
Sept. 1992

Abstract: This Technical Notes describes the proper design and detailing of a variety of brick paving assemblies. Design considerations covered include traffic, site conditions, drainage, edge restraints, joints and appearance. Typical details of various mortarless and mortared brick paving assemblies are shown. 

INTRODUCTION

Since brick is derived from the earth, it is only natural that it be used as a paving material. Brick is a small element paving material which provides an aesthetically pleasing, stable and durable surface. Brick paving assemblies are comprised of the brick surface along with a base to provide support. In any paving assembly, the base is of prime importance, for if it is improperly designed or constructed, the entire system is prone to failure.

This Technical Notes series discusses a variety of brick paving assemblies for residential and commercial applications. Although the principles are the same for all brick paving assemblies, the recommendations may not be appropriate for industrial type floors or heavy vehicular applications. Further information on flexible brick pavements in road and street applications can be found in the Brick Institute of America's Flexible Brick Pavements: Design and Installation Guide [1]. This Technical Notes classifies paving assemblies by type of paving surface and type of base. Design considerations are given for traffic loads, drainage, site conditions, edge restraints, expansion joints, membranes, slip/skid resistance and appearance. Other Technical Notes in this series address material selection, installation techniques and special brick paving assemblies.

CLASSIFICATION OF PAVING ASSEMBLIES

Paving assemblies are classified by the type of brick paving surface and the type of base supporting the surface. The paving surface receives the traffic wear, protects the base and transfers loads to the base. The base and subbase (if required) provide structural support to the paving system by distributing the load to the subgrade. A subbase consisting of graded aggregates may be required when subgrade conditions are poor.

Types of Brick Paving Surfaces

The two types of brick paving surfaces are mortarless and mortared. Mortarless brick paving contains sand between the units which are laid on a variety of materials. Conversely, mortared brick paving consists of units with mortar between the units and always laid in a mortar setting bed.

Types of Bases

Flexible Base. A flexible base consists of compacted crushed stone, gravel or coarse sand. Only mortarless brick paving is suitable for this type of base.

Semi-Rigid Base. This type of base consists of asphalt concrete, commonly referred to as asphalt. Only mortarless brick paving is suitable over this type of base.

Rigid Base. A rigid base is defined as a reinforced or unreinforced concrete slab on grade. Mortarless or mortared brick paving may be placed over this type of base.

Suspended Diaphragm Base. Suspended diaphragm bases are structural roof or floor assemblies of concrete, steel or wood. Mortarless or mortared brick paving is suitable for this type of base depending on the stiffness of the diaphragm.

EXAMPLES OF BRICK PAVING ASSEMBLIES

Many combinations of bases, setting beds and brick paving surfaces can be used. The paving assemblies included are suggested methods based on experience for the various types of traffic uses. Although not all potential paving assemblies are shown due to space limitation, the following are the most popular configurations.

Flexible Base Pavements

Only mortarless brick paving should be laid over a flexible base. Flexible bases include crushed stone, gravel or coarse sand. Applications for flexible bases range from residential patios to city streets. Flexible paving systems are typically the most economical to install since less labor and fewer materials are involved. The thickness of each layer in a flexible pavement depends upon the imposed loads and the properties of each layer. A pavement subjected to heavy vehicular traffic requires a thicker base than a pavement subjected to pedestrian traffic.

Figure 1 is a typical section through a flexible brick pavement. Brick pavers are set in a 1 in. to 1 1/2 in. (25 to 38 mm) sand setting bed over a compacted base, subbase (if necessary) and compacted subgrade. Many commercial pedestrian and vehicular applications can use this type of assembly. Pavements subjected to vehicular traffic must be designed to accommodate the wheel loads. The Flexible Brick Pavements design guide covers design and installation requirements for heavy vehicular loading.

Mortarless Brick Paving
Aggregate Base
FIG. 1

In residential pedestrian applications, the detail in Fig. 2 can be used. The brick pavers are laid directly on the compacted sand and subgrade. This application works best when the subgrade is compacted or on undisturbed earth, and where frost heave is not a consideration. A geotextile can be used beneath the sand base where the soil conditions are poor.

Mortarless Brick Paving
Sand Base
FIG. 2

Semi-Rigid Base Pavements

Asphalt bases are classified as semi-rigid bases. Only mortarless brick paving is suitable over this type of base. Figure 3 is an example of an asphalt base and an asphalt setting bed supporting the mortarless brick paving. The mortarless brick paving and asphalt setting bed can also be laid on a concrete base. These assemblies are suitable for medium to heavy vehicular traffic, pedestrian malls or other pedestrian areas.

Mortarless Brick Paving
Asphalt Base
FIG. 3

The detail shown in Fig. 4 is another paving assembly on a semi-rigid base. Two layers of No. 15 building felt or one layer of No. 30 felt act as a cushion between the brick pavers and the base and help accommodate size variations. This detail is only suitable for residential pedestrian applications.

Mortarless Brick Paving
Concrete or Asphalt Base
FIG. 4

Rigid Base Pavements

Mortarless or mortared brick paving may be laid over a rigid concrete base. The brick paving assembly shown in Fig. 4 is applicable for mortarless paving over a new or existing concrete slab. Only residential pedestrian applications are appropriate for this assembly. A similar assembly is shown in Fig. 5 where sand is used as a setting bed. These assemblies are not appropriate in vehicular applications, areas of large rainfall or in freezing climates where the pavement may heave when saturated.

Mortarless Brick Paving
Concrete Base
FIG. 5

Figure 6 shows a typical example of mortared brick paving over a reinforced concrete slab on grade. Mortared brick paving can be used for any type of pedestrian or vehicular traffic in both interior and exterior applications. This type of assembly is especially well-suited for heavy vehicular areas such as streets or parking lots and where surface drainage is necessary.

Mortared Brick Paving
Concrete Base
FIG. 6

DESIGN CONSIDERATIONS

Traffic

The weight and amount of traffic often dictate which paving system to use. The brick paving assembly must be capable of supporting traffic loads plus its own weight. The appropriate thickness of the subbase, base and brick paving units must be considered to adequately distribute vertical traffic loads. Three general classifications of traffic are light, medium and heavy, and should be considered when determining the subbase, base and brick paver thicknesses. The classifications of traffic are defined as follows:

Light Traffic. Residential pedestrian traffic only, such as on patios and walkways.

Medium Traffic. Commercial pedestrian traffic, such as on city sidewalks, building entrances and shopping malls. Light vehicular traffic, such as on residential driveways, commercial entranceways and parking lots.

Heavy Traffic. Heavy vehicular traffic, such as streets, crosswalks, loading docks and roads. The term heavy refers to both axle loads and frequency of loading.

Heavy vehicular traffic on grade will generally require rigid, semi-rigid, or thick flexible bases. Medium and light traffic may be supported on any of these or on suspended diaphragms.

Load Resistance

Vertical Loads. Vehicular traffic, pedestrian traffic and the weight of the paving assembly impose vertical loads upon the paving system. These loads are distributed to each pavement layer in a radiating manner. Each layer resists a proportion of the load depending on its strength and thickness. The most important aspect of designing the pavement to resist vertical loads is determining the appropriate thickness of the base. Inadequate base thickness will result in premature failure of the paving system, while excessive thickness will result in increased costs. For light and medium traffic applications, the minimum required thickness of each base material will normally govern. Pavements subjected to vehicular traffic, other than residential driveways, generally require design by an engineer.

Base Thickness — The minimum thickness of an aggregate base depends primarily upon the strength of the subgrade. Typically, a flexible base of properly graded crushed stone or gravel should be a minimum thickness of 4 in. (100 mm). The minimum thickness of a reinforced concrete or an asphalt base in pedestrian and light vehicular traffic applications is 4 in. (100 mm), provided it bears on adequate subgrade. Concrete and asphalt bases usually require a subbase. Very heavy loading requires an increase in thickness for all types of bases. Additional information on base design is available from the appropriate reference [2,7].

Paving Surface Thickness — A mortarless brick paving surface can be supported on a flexible base, a semi-rigid base, a rigid base or a suspended diaphragm. Typically the base is designed to resist vertical loads independent of the brick paving surface. However, the brick paving surface does, in fact, contribute to the load-carrying capabilities of the pavement and may be considered in design if it is of sufficient thickness and constructed properly. In order for the brick pavers to be considered when calculating thickness, they must be compacted into place as described in Technical Notes 14A and the Flexible Brick Pavements design guide. If brick pavers are not compacted into place, they should be neglected in the pavement thickness design but still must meet certain minimum thicknesses to act as a wearing surface. These suggested minimum thicknesses for mortarless brick paving are: light traffic, 1 1/2 in. (38 mm); medium traffic, 2 1/2 in. (57 mm); and heavy traffic, 2-5/8 in. (67 mm). In order for the brick pavers to be considered in resisting load they must have a 2-5/8 in. (67 mm) minimum thickness, excluding chamfers, to achieve interlock. Interlock is the effect of frictional forces, induced by sand beneath and between the brick pavers, which restricts movement of the paver and transfers loads between adjacent pavers. In the case of heavy traffic, the brick pavers and sand setting bed are compacted into place and contribute to the load-carrying capabilities of the system.

A mortared brick paving surface should always be supported by a rigid base or suspended diaphragm. Without a rigid support, the paving system will deflect and cause cracking in the brick paving surface. The primary resistance to vertical loading is developed by the flexural strength of the concrete slab on grade or the roof or floor diaphragm. There is no minimum thickness for the paving unit to adequately transfer vertical loads. The required thickness to perform adequately as a result of horizontal loads and pavement deflection is in the range of 1/2 in. (13 mm) to 2 1/4 in. (57 mm) depending on traffic conditions and slab support. Thicker pavers are more likely to stay in place in the event of cracking.

Horizontal Loads. In addition to vertical loads, vehicular traffic imparts horizontal forces to the paving assembly from braking, acceleration and turning actions of the wheels. Resistance to horizontal forces is provided by the bond pattern of the brick paving assembly, the pavement edging and the bond of the brick units to the base.

Mortarless brick paving resists horizontal forces by transferring these forces through brick units and sand filled joints to rigid edging by means of an interlocking bond pattern. The greatest resistance to horizontal forces is obtained when the direction of vehicular traffic flow is perpendicular to the long joints in the bond pattern. Therefore, continuous joints in running bond and other bond patterns should be laid perpendicular to the traffic flow. The herringbone bond pattern resists loads in all directions and should be used in heavy vehicular areas.

Mortared brick paving resists horizontal forces imparted by vehicles due to the bonding of the units to the base by the mortar setting bed and full head joints. Thus, bond pattern and unit orientation are not critical for load transfer in mortared paving.

Drainage

Adequate drainage of flexible and rigid paving systems is an extremely important design consideration for successful performance and durability. Ponding water can cause deterioration of the paving in areas of repeated freeze/thaw and cause slippery conditions. Continued saturation of the base, subbase and subgrade can reduce load capacity due to weakening of the soil and cause deformations or rutting of the pavement.

The best way to obtain drainage of the pavement is to slope the paving surface to provide as much surface drainage as possible. A slope of 1/8 in. to 1/4 in. per ft (1 to 2 mm per 100 mm) is suggested. Large paved areas and vehicular traffic areas may require a slope greater than 1/4 in. per ft (2 mm per 100 mm). The paving system should be sloped away from buildings, retaining walls and other elements capable of collecting or restricting surface runoff. To improve surface drainage, the direction of continuous mortar joints should run parallel to the desired direction of surface runoff.

Mortarless paving requires both surface and subsurface drainage. The majority of drainage should occur on the surface. However, some water will penetrate downward until it reaches an impervious layer. This layer may be a concrete or asphalt base, a flexible base compacted to high density, an impervious soil such as clay or an impervious membrane used to separate pavement layers. Water not drained off the pavement surface will percolate to the top of this impervious layer, possibly causing pending of the water. Due to these conditions, subsurface drainage is required.

Mortarless brick paving constructed over a porous base such as gravel may permit drainage through the entire system to the subgrade. The use of a geotextile between the sand setting bed and the base will permit drainage without allowing migration of the sand setting bed into the base.

Drainage in mortared brick paving systems is restricted to the surface by full mortar joints and good bond between the brick paving units and the mortar. A drainage system should be designed so standing water is kept to a minimum.

Surface runoff is removed by pavement edge drainage or by drains within the paving. Drains and drainage systems must be designed to remove the anticipated amount of water. The amount of drainage required varies with the size and location of the pavement and the amount of annual rainfall. Most commercial paving applications require gutters, scuppers or surface grates for surface drainage. In subsurface drainage applications, drains should have slotted openings on all sides below the paving surface. Setting bed material should be protected from washout into the drains by the use of screens or geotextiles.

To prevent water from pending against curbs, weepholes should be installed through the curb at a maximum spacing of 24 in. (600 mm) o.c. along the entire edge. The weepholes should be formed by tubes or pipes with sufficient size to allow water drainage. Curb gutters can also be used when the gutter is sloped toward a drain. Figures 7 and 8 are examples of drainage in flexible and rigid base paving systems.

Drainage of Flexible Paving
Aggregate Base
FIG. 7

Drainage of Rigid Paving
FIG. 8

Site

The site may involve anything from a small residential patio to a major urban renewal project encompassing several city blocks. During the planning stages, consideration should be given to the location of existing or proposed underground utilities and storm drains convenient to the user. Flexible brick pavements are ideal in areas where frequent underground work will be required since removal and reinstallation is easy and existing materials can be reused.

Successful installations also depend upon proper subgrade preparation. All vegetation and organic materials should be removed to the proper depth from the area to be paved. Soft spots such as utility trenches containing poor subbase material should be removed and refilled with suitable material which is properly compacted.

Edge Restraints

Many different types of edge restraint materials exist, Including brick, rigid plastic, wood, stone, steel, aluminum and concrete. Existing walls or structures may also be used as an edge restraint. The particular application and site conditions determine which material to use. Any of the materials previously listed can be used in light traffic applications. Only concrete, brick or stone embedded in concrete, some varieties of rigid plastic, or metal should be used in areas subjected to light or medium traffic. Heavy traffic applications require cast-in-place concrete, granite or curbs of equal strength. Asphalt or an asphalt pavement does not provide adequate edge restraint for paving subjected to vehicular traffic.

Edge restraints are necessary in mortarless brick pavements as they hold the pavers together and prevent spreading and movement of pavers due to horizontal traffic loads. Intermediate restraints may be used within the pavement when there is an interruption in the paving surface or on sloped or curved areas. Intermediate restraints will provide additional thrust resistance to traffic loads and pavement creep.

Edge restraints are not necessary in mortared brick paving but may be used for aesthetic reasons, to reduce chipping of perimeter brick or to control landscaping. Any of the edge restraint materials mentioned may be used.

Expansion Joints

Due to differential moisture and temperature changes, allowances for movement of various materials which comprise the paving assembly should be considered. Expansion joints are used in the brick paving to accommodate these movements. Expansion joint size and location vary for each paving assembly relative to climate, location, orientation, paving unit color and exposure to solar radiation. Although there are numerous formulae and guides for predicting the anticipated movement of materials, proper joint placement often depends on experience gained from similar past paving applications, along with good engineering judgment.

Mortarless brick paving usually has the ability to move slightly and accommodate size changes. Consequently, expansion joints in mortarless brick paving are not generally required.

Placement of expansion joints is critical in mortared brick paving assemblies. Expansion joints in brick paving which is bonded to the base must align with control joints in the concrete base below. If this is not possible, a bond break between the mortar setting bed and concrete slab must be used. However, this may not be sufficient to prevent cracking of the mortared brick paving near the control joint location. A typical expansion joint in mortared brick paving is shown in Fig. 9.

In most cases, an expansion joint spacing of 16 ft (5 m) in exterior mortared brick paving is adequate. Expansion joints in interior mortared brick paving may be spaced a maximum of 24 ft (7 m) apart. However, these distances are dependent on many factors and local conditions including

Expansion Joints
FIG. 9

those described above. Dimensions should be measured at right angles to each other in order to keep the recommended distances from being exceeded in either direction. Expansion joint material should be placed along fixed objects such as drains or adjacent walls. Suggested placement of expansion joints for mortared brick paving are shown in Fig. 10.

Expansion joint filler materials must be highly compressible and be durable when exposed to weather or abrasion. Generally, paving joint fillers made of materials such as polyethylene or premolded cellular elastomeric rod are acceptable. Materials which do not easily compress, such as cork or asphaltic control joint fillers, are not appropriate expansion joint fillers. The top of the joint is sealed with an elastomeric sealant.

Typical Expansion Joint Placement In Mortared Brick Paving

FIG. 10

Membranes

Membranes are used in brick paving applications to separate layers in a paving system, accommodate differential movement or serve as a waterproofing element. Membrane materials include geotextiles, sheet membranes and liquid membranes.

Flexible Base Pavements. In flexible base applications geotextiles may be used to separate layers. In some cases, poor soil conditions may warrant the use of a geotextile to prevent subgrade soil from migrating upward into the compacted subbase or base. In other cases an open-graded, stone base may require a geotextile above it to prevent the sand setting bed from filtering down through the base. The opening size of the geotextile should be small enough to prevent sand filtration. Geotextiles can also be used to prevent erosion or used to reinforce the subgrade. If used to reinforce the subgrade, the sections of geotextile must be lapped a minimum distance. Consult the geotextile manufacturer for specific recommendations. Building felt and other impervious membranes should not be used since they inhibit drainage.

Rigid Base Pavements. Mortared brick paving and concrete bases have considerably different thermal and moisture movements. In applications where the spacing between expansion joints is larger than 16 ft (5 m), it is important to break the bond between the rigid base and the mortar setting bed by means of a membrane. Polyethylene plastic sheets or building felt can be used as the bond break. The bond break will allow the brick paving surface to move independently of the base, but still permit the paving system to provide the necessary transfer of loads. Bond breaks should be used when the brick expansion joint and concrete control joint are not aligned.

Waterproofing is used in roof deck applications where it is important to prevent water penetration. The waterproofing is often applied in liquid form but can also be sheet membranes. Care should be taken to prevent damage or penetrations to waterproofing membranes during pavement construction. Technical Notes 14B provides details for brick paving over roof decks.

Slip and Skid Resistance

The slip resistance characteristics of a paving surface relate to pedestrian traffic, while skid resistance characteristics relate to vehicular traffic. Slip and skid resistance are measures of the slipperiness of a surface. A surface with high slip or skid resistance is relatively safe, while a low resistance may indicate a hazardous surface. Both slip resistance and skid resistance are adversely affected by water on the surface of the pavement.

It is the surprise of walking from a slip resistant surface onto a wet or nonslip resistant surface that causes many falls. Since the slip resistance relies on the microtexture of the paving brick, a brick with a rougher or wire cut surface will have a higher slip resistance.

Skid resistance measures the potential of vehicles skidding on the roadway surface. The skid resistance depends upon the macrotexture of the paving surface. Brick texture, joints between pavers and pavers with chamfered edges have positive effects on the overall skid resistance of the brick pavement. Skid resistance values of brick pavers fall within the range of concrete and asphalt pavements [5].

Over time, the skid resistance of all paving surfaces decreases because of the polishing effect of traffic.. The skid resistance of most brick paving is initially very high and decreases while in use, approaching an equilibrium condition after one year [8]. The skid resistance values are also affected by seasonal factors.

Aesthetics

The visual impact of brick paving results from the interplay of many factors including size, shape, pattern, color and texture. An endless variety of bond patterns can be achieved with brick paving. The most popular paving patterns are shown in Fig. 11. These patterns may be laid with or without mortar joints. Patterns such as herringbone, basketweave variations and some running/stack bond combinations require brick pavers with lengths twice its width when laid in mortarless brick paving. Two examples of paver sizes appropriate for mortarless paving bond patterns are 4 in. (100 mm) by 8 in. (200 mm) and 3 3/4 in. (95 mm) by 7 1/2 in. (190 mm). For mortared brick paving, nominal dimensions are often used where the paving unit dimensions listed include the mortar joint thickness. Thus, when laying out patterns with mortar joints, it is best to use nominal dimensions.

Brick Paving Patterns
FIG. 11

Brick pavers are manufactured in a variety of colors such as reds, browns, buffs, grays and others, including ranges and blends of colors. The type of traffic on the paving units should be considered when choosing color. For example, a light colored brick will show dirt and stains more than a darker colored brick. Also, color patterns can serve a function. Two or more different colors can be used to create patterns which guide traffic, such as marking traffic lanes or parking spaces.

SUMMARY

This Technical Notes describes brick paving assemblies and covers their design and detailing. Critical design concerns in brick paving systems include base preparation, drainage and load resistance. Pertinent design criteria is provided to aid the development of a proper brick paving system. The details provided in this Technical Notes will provide an adequate pavement system for most applications.

The information and suggestions contained in this Technical Notes are based on the available data and the experience of the engineering staff of the Brick Institute of America. The information contained herein must be used in conjunction with good technical judgment and a basic understanding of the properties of brick masonry. Final decisions on the use of the information contained in this Technical Notes are not within the purview of the Brick Institute of America and must rest with the project architect, engineer and owner.

REFERENCES

Brick Floors & Pavements

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