ICPI provides construction guidelines to design professionals and installers of interlocking concrete pavements. Several resources are available on this website that review the steps necessary for constructing interlocking concrete pavements.

This pavement structure is commonly used for both pedestrian and vehicular applications. Pedestrian areas, driveways, and areas subject to limited vehicular use are paved with units 2 3/8 in. (60 mm) thick. Streets and industrial pavements should be  paved with units at least 3 1/8 in. (80 mm) thick.

Compaction of the soil subgrade and aggregate base materials are essential to the long-term performance of interlocking concrete pavements.

Installation steps typically include job planning, layout, excavating and compacting the soil subgrade, applying geotextiles (optional), spreading and compacting the sub-base and/or base aggregates, constructing edge, restraints, placing and screeding the bedding sand, placing concrete pavers, compacting concrete pavers, sweeping in jointing sand and final compaction.

Installation Basics

Note: The elevations and surface tolerance of the soil subgrade determine the final surface elevations of concrete pavers. The paver installation contractor cannot correct deficiencies excavation and grading of the soil subgrade with additional bedding materials. Therefore, the surface elevations of the soil subgrade should be checked and accepted by the General Contractor or designated party, with written certification presented to the paver installation subcontractor prior to starting work.

A.   Acceptance of Site Verification of Conditions:

1.   General Contractor shall inspect, accept and certify in writing to the paver installation subcontractor that site conditions meet specifications for the following items prior to installation of interlocking concrete pavers.

  • Note: Compaction of the soil subgrade is optional and should be determined by the project engineer. If the soil subgrade requires compaction, compact to a minimum of 95% standard Proctor density per ASTM C 698. Compacted soil density and moisture should be checked in the field with a nuclear density gauge or other test methods for compliance to specifications. Stabilization of the soil and/or base material may be necessary with weak or continually saturated soils, or when subject to high wheel loads. Compaction will reduce the permeability of soils. If soil compaction is necessary, reduced infiltration may require drain pipes within the open-graded subbase to conform to local storm drainage requirements.
  •   Verify that subgrade preparation, compacted density and elevations conform to specified requirements.
  •   Provide written density test results for soil subgrade to the Owner, General Contractor and paver installation subcontractor.
  •   Verify location, type, and elevations of edge restraints, [concrete collars around] utility structures, and drainage pipes and inlets.

2.   Do not proceed with installation of bedding and interlocking concrete pavers until subgrade soil conditions are corrected by the General Contractor or designated subcontractor.


A.   Verify that the soil subgrade is free from standing water.

B.   Stockpile joint/opening filler, base and subbase materials such that they are free from standing water, uniformly graded, free of any organic material or sediment, debris, and ready for placement.

C.   Edge Restraint Preparation:

  • 1.   Install edge restraints per the drawings [at the indicated elevations].

Note: The minimum slope of the soil subgrade is typically 0.5%. Actual slope of soil subgrade will depend on the drainage design and exfiltration type. All drain pipes, observation wells, overflow pipes, and (if applicable) geotextiles, berms, baffles and impermeable liner should be in place per the drawings prior to or during placement of the subbase and base, depending on their location. Care must be taken not to damage drainpipes during compaction and paving. No mud or sediment can be left on the base or bedding aggregates. If they are contaminated, they must be removed and replaced with clean materials. Base/subbase thicknesses and drainage should be determined using ICPI’s Permeable Interlocking Concrete Pavements manual and Permeable Design Pro software.


A.   General

1.   Any excess thickness of soil applied over the excavated soil subgrade to trap sediment from adjacent construction activities shall be removed before application of the [geotextile] and subbase materials.

2.   Keep area where pavement is to be constructed free from sediment during entire job. [Geotextiles] Base and bedding materials contaminated with sediment shall be removed and replaced with clean materials.

3.   Do not damage drainpipes, overflow pipes, observation wells, or any inlets and other    drainage appurtenances during installation. Report any damage immediately to the project engineer.       

B.   Geotextiles

1.   Place on [bottom and] sides of soil subgrade. Secure in place to prevent wrinkling from vehicle tires and tracks.

2.   Overlap a minimum of [0.3 m (12 in.)] [0.6 m (24 in.)] in the direction of drainage.

C.   Open-graded subbase and base


Note: Compaction of areas or sites that cannot accommodate a roller vibratory compactor may use a minimum 13,500 lbf (60 kN) vibratory plate compactor with a compaction indicator. At least two passes should be made over each lift of the subbase and base aggregates.


1.   Moisten, spread and compact the No. 2 subbase in 4 to 6 in. (100 to 150 mm) lifts [without wrinkling or folding the geotextile. Place subbase to protect geotextile from wrinkling under equipment tires and tracks.]

2.   For each lift, make at least two passes in the vibratory mode then at least two in the static mode with a minimum 10 t (8 T) vibratory roller until there is no visible movement of the No. 2 stone. Do not crush aggregate with the roller.

3.   The surface tolerance of the compacted No. 2 subbase shall be ±2 1/2 in. (± 65mm)    over a 10 ft (3 m) straightedge.

4.   Moisten, spread and compact the No. 57 base layer in one 4 in. (100 mm) thick lift.

  •       On this layer, make at least two passes in the vibratory mode then at least two in the static mode with a minimum 10 t (8 T) vibratory roller until there is no visible movement of the No. 57 stone. Do not crush aggregate with the roller.
  • Note: At the option of the designer, this supplemental test method bracketed in items 5 through 9 below can be used to establish a consistent methodology for in-situ density data collection of open-graded aggregate base layer (typically ASTM No. 57 stone). This test method can assist contractors in reaching adequate job site compaction and offer an additional level of confidence for the project owner and designer. This test method is appropriate for pavement subject to consistent vehicular traffic such as parking lots and roads. It is not needed for pedestrian areas and residential driveways. Other test methods should be considered to check consistent compaction of the soil subgrade (when specified), the aggregate subbase and base layers, and the pavers. These include stiffness measurements using a Geogauge per ASTM D 6758 or a Zorn Lightweight Deflectometer per ASTM E 2835.

5.    Use part of the compacted base area as a control strip for density testing by the    [Testing Company].

  • The [Testing Company] shall supply nuclear moisture/density gauges and ancillary  equipment required to conduct density and moisture content measurements for compaction of the No. 57 aggregate drainage layer. Qualified testing laboratory  operators/gauges may conduct compaction testing. Each gauge operator shall be  trained in the safe operation, transportation and handling of the gauge. The  registered owner of the gauge shall have and maintain a valid Radioisotope License for each gauge.
  • Each gauge shall have been calibrated within the last 12 months, either by the manufacturer or other qualified agent, against certified density and moisture reference blocks. The density standard count and the moisture standard count shall be within 2 percent and 4 percent respectively, of the most recent calibration values. A certificate of calibration for each gauge shall accompany each gauge. 

6.   Target Density

  •  Determine a target density on the control strip during under the following conditions:
    •  (1) after initial placement and compaction of the base aggregate layer
    • (2) when there is a perceptible change in the appearance or gradation of the aggregate,
    • (3)    when there is a change in the source of aggregate.
  • Test field density according to ASTM D 2922 Standard Test Methods for Density of Soil and Soil-Aggregate In-Place by Nuclear Methods (shallow Depth). Field density tests shall be performed on compacted base materials to determine within acceptable limits of a target density.

 7.   Control Strip

  • The Testing Company shall construct a control strip for the determination of a target   density consisting of a single uniform lift as specified in the contract documents, but not more than 4 in. (100 mm) thick and covering approximately 600 yd2 (500 m2) in area. No testing shall be performed within 10 ft (3 m) from any unrestrained outside edge of the work area. The control strip may be incorporated into the project upon acceptance of density measurements by the Testing Company.
  • During construction of the control strip, the surface of the aggregate shall be visibly moist and maintained as such throughout construction and compaction.
  • After initial placement of the aggregate base material, the compaction equipment shall make two passes over the entire surface of the control strip. Field densities and field moisture contents, using the backscatter/indirect method, shall be determined at five randomly selected locations at least 15 ft (5 m) apart. The dry density and moisture content shall be calculated for each of these locations and the averages shall be used as initial values. The maximum compacted thickness of the aggregate base layer measured for density shall be 4 in. (100 mm).

  • The compaction equipment shall then make two additional passes over the entire surface of the control strip. After compaction, three separate, random field density and moisture content determinations shall be made, using the backscatter/indirect method, and a new average dry density and moisture content shall be calculated. 
  • If the new average dry density exceeds the previous value by more than 1.2 pcf (20 kg/m3) then two additional passes of the equipment shall be carried out as described above. If the new average dry density does not exceed the previous value by more than 1.2 pcf (20 kg/m3), then compaction of the control strip will be considered satisfactory and complete.
  • Upon satisfactory completion of the control strip, an additional seven (7) field density and moisture tests, using the backscatter/indirect method, shall be taken at random locations and the dry density and moisture content values shall be determined. The final dry density and moisture content of the control strip shall be the average of these seven values plus the three most recent values obtained upon completion. 

8.    Compaction

a. Use a smooth dual or single smooth drum, minimum 10 t (8 T) vibratory roller or a

minimum 13,500 lbf (60 kN), reversible vibratory plate compactor with a compaction indicator without crushing the aggregate base.

b. Compact aggregates without crushing them.

9.   Test Report

The test report shall include the following:

  1. Project description.
  2. Sketch of test area and test locations.
  3. Aggregate type and layer thicknesses.
  4. Aggregate characteristic properties: gradation, void ratio, bulk density.
  5. Compaction equipment type and weight.
  6. Static or vibratory compaction.
  7. Number of passes of the compaction equipment.
  8. Test number and location.
  9. Individual and average field wet density, moisture content, and dry density values determined after each compaction operation in accordance with ASTM D 2922 Standard Test Methods for Density of Soil and Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
  10. Calculation of target density.]


  •   The surface tolerance the compacted No. 57 base should not deviate more than. ±1 in. (25  
  •    mm) over a 10 ft (3 m) straightedge.


Note: As an alternative test method, in-place density of the base aggregate may be checked per ASTM D 4254. Compacted density should be 95% of the laboratory index density established for the base layer.


 E.  Bedding layer

  •  Moisten, spread and screed the No. 8 stone bedding material.
  •  Fill voids left by removed screed rails with No. 8 stone.
  •   The surface tolerance of the screeded No. 8 bedding layer shall be ±3/8 in (10 mm) over a 10 ft (3 m) straightedge.
  •    Do not subject screeded bedding material to any pedestrian or vehicular traffic before paving unit installation begins.

 F.          Permeable interlocking concrete pavers and joint/opening fill material

  •   Lay the paving units in the pattern(s) and joint widths shown on the drawings. Maintain straight pattern lines.
  •   Fill gaps at the edges of the paved area with cut units. Cut pavers subject to tire traffic shall be no smaller than 1/3 of a whole unit.
  •   Cut pavers and place along the edges with a [double-bladed splitter or] masonry saw.
  •   Fill the openings and joints with [No. 8] stone.
  • Note: Some paver joint widths may be narrow and not accept most of the No. 8 stone. Use joint material that will fill joints such as washed ASTM No. 89 or No. 9 stone.
  •   Remove excess aggregate on the surface by sweeping pavers clean.
  •    Compact and seat the pavers into the bedding material using a low-amplitude, 75-90 Hz plate compactor capable of at least 5,000 lbf (22 kN). This will require at least two passes with the plate compactor.
  • Do not compact within 6 ft (2 m) of the unrestrained edges of the paving units.
  •  Apply additional aggregate to the openings and joints if needed, filling them completely. Remove excess aggregate by sweeping then compact the pavers. This will require at least two passes with the plate compactor. 
  •   All pavers within 6 ft (2 m) of the laying face must be left fully compacted at the completion of each day.
  •  The final surface tolerance of compacted pavers shall not deviate more than ±3/8 (10 mm) under a 10 ft (3 m) long straightedge.
  •  The surface elevation of pavers shall be 1/8 to 1/4 in. (3 to 6 mm) above adjacent drainage inlets, concrete collars or channels.

A.   After sweeping the surface clean, check final elevations for conformance to the drawings.

B.   Lippage: No greater than 1/8 in. (3 mm) difference in height between adjacent pavers.

Note: The surface of the pavers may be 1/8 to 1/4 in. (3 to 6 mm) above the final elevations after compaction. This helps compensate for possible minor settling normal to pavements.

C.   The surface elevation of pavers shall be 1/8 to 1/4 in. (3 to 6 mm) above adjacent drainage inlets, concrete collars or channels.

D.   Bond lines for paver courses: ±½ in. (±15 mm) over a 50 ft (15 m) string line.

E.   Verify the surface infiltration at a minimum of 100 in./hour using test method C 1781.


A.   After work in this section is complete, the General Contractor shall be responsible for protecting work from sediment deposition and damage due to subsequent construction activity on the site.

B.   PICP installation contractor shall return to site after 6 months from the completion of the work  and provide the following as required: fill paver joints with stones, replace broken or cracked pavers, and re-level settled pavers to initial elevations. Any additional work shall be considered part of original bid price and with no additional compensation.