Construction Tolerances and Recommendations

for Interlocking Concrete Pavements

Note: This guide does not apply to permeable interlocking concrete pavements or tumbled pavers

Concrete Pavers with

Edge sand filled joints
Restraint/
Curb Bedding Sand
nominal 1 in. (25 mm)
Compacted aggregate
or stabilized base to
suit traffic and
environmental
conditions

Geotextile as required
by design

Compacted soil
Typical Components of an subgrade
Interlocking Concrete Pavement

Paver and bedding layer Base and subbase layer

Attribute Tolerance* Attribute Tolerance*
Paver joint width 1/16 in. (2 mm) to max. 3/16 in. (5 mm) Top of base surface variation ± 3/8 in. (10 mm) over 10 ft. (3 m)
Paver surface flatness ±3/8 in.(10 mm) in 10 ft. (3 m) (non cum.) (non cumulative)
Lippage at catch basins/drains 1/8 in. to 3/8 in. (3 to 10 mm) (non ADA)

Lippage between individual pavers maximum 1/8 in. (3 mm) for pedestrian access routes
Attribute ICPI recommendation
Base thickness variation3 + 3/4 in. to -1/2 in. (+20 mm to -13 mm)
Attribute ICPI recommendation Compaction min. 98% standard Proctor
Paver aspect ratio (l:t) max. 4:1 for pedestrian & driveways Over-excavation greater of 6 in. (150 m) or equal
(length divided by thickness) max. 3:1 for street/parking
(dense graded bases) to base thickness
Joint fill depth max.1/2 in. (13 mm) measured from top
Geotextile as needed
of pavement
Bond lines1 ±1/2 in. (13 mm) max. over 50 ft. (16 m) Minimum base thickness4
Slope for drainage min. 2% Sidewalks, patios, pedestrian 4 in. (100 mm)
Cut pavers5 No less than 1/3 for Residential driveways 6 in. (150 mm)
vehicular application Parking lot/residential street 8 in. (200 mm)
No less than 3/8 in. (10 mm) for all
other applications
Paver laying pattern2 Acceptable for application Edge restraint/curb edge
Minimum paver thickness 31/8 in. (8 cm) for street/parking
23/8 in. (6 cm) for pedestrian & driveways Attribute ICPI recommendation
Bedding layer thickness 1 in. (25 mm) nominal No movement firmly in place
Joint sand gradation ASTM C144 or C33 Proper restraint acceptable for application
CSA A23.1 FA1 or CSA A179 (see “Guide References” on reverse)
Bedding sand gradation ASTM C33 or CSA A23.1 FA1
Notes:
1
Bond lines: Unless it is deemed that the pavement is not adequately restrained at the edges the bond line tolerance is considered cosmetic
2
Paving layer pattern: ICPI recommends herringbone laying pattern for all vehicular applications
Base thickness variation: An example of an acceptable variation is 71/2 in. to 83/4 in. (190 to 220 mm) for an 8 in. (200 mm) required total base thickness.
3

The excavated cut should have the same slope and contouring as the final surface profile.
4
Minimum base thickness: These are for well drained soils. Increase thickness in colder climates or weak soils.
The contractor should have the discretion on cuts no less than 1/3 paver size. Sometimes it is not possible to adjust the cuts to less than 1/3 paver size
5

without adjusting laying pattern, and sometimes it is not possible to adjust laying pattern with certain shapes.
*See reverse for tolerance measurement guidance

Interlocking Concrete Pavement Institute • 13921 Park Center Road, Suite 270 • Herndon, VA 20171
Tel: (703) 657-6900 • Fax: (703) 657-6901 • Email: icpi@icpi.org • Web: icpi.org
Guide References
Specification and design references
ASCE/ANSI Structural Design of Interlocking Concrete Pavements – pre-standard
ICPI Tech Spec 4–Structural Design of Interlocking Concrete Pavement for Roads and Parking Lots
ICPI Tech Spec 9–Guide Specification for the Construction of Interlocking Concrete Pavement
ICPI Lockpave software www.icpi.org

Pavement system references

ASTM C936 Standard Specification for Solid Interlocking Concrete Paving Units
CSA A231.2 Precast Concrete Pavers
ICPI Tech Spec 1–Glossary of Terms for Segmental Concrete Pavement
ICPI Tech Spec 2–Construction of Interlocking Concrete Pavements
ICPI Tech Spec 4–Structural Design of Interlocking Concrete Pavement for Roads and Parking Lots
ICPI Tech Spec 5–Cleaning, Sealing and Joint Sand Stabilization of Interlocking Concrete Pavement

Bedding and joint sand references

ASTM C33 Standard Specification for Concrete Aggregates
CSA A23.1 Concrete Materials and Methods of Construction
ASTM C144 Standard Specification for Aggregate for Masonry Mortar
CSA A179 Mortar and Grout for Unit Masonry
ICPI Tech Spec 17–Bedding Sand Selection for Interlocking Concrete Pavements in Vehicular Applications

Base, subbase and subgrade layer references

ASTM D 2940 Standard Specification for Graded Aggregate Material For Bases or Subbases for Highways or Airports
ICPI Tech Spec 2–Construction of Interlocking Concrete Pavements
ASTM D698 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort

Edge restraint references

ICPI Tech Spec 3–Edge Restraints for Interlocking Concrete Pavements

Tolerance Measurement Guidance

CHAMFER (TYP.)

MAX. 1/8 IN. (3 MM)

1/16 TO 3/16 IN.

(2 TO 5 MM)

Joint widths are measured with a ruler from inside edge Lippage is measured from the top of a paver to the top of the adjacent
of paver to inside edge paver between adjacent pavers paver

SURFACE FLATNESS TOLERANCE

10 FT (3 M) LONG STRAIGHT EDGE MAX. ±3/8 IN. (10 MM), NON CUMULATIVE

Paver surface flatness and top of base surface variation are measured with a straight edge for simple slopes and with a transit for complex contours