Note: Compaction of the soil subgrade is recommended to a minimum of 95% standard Proctor density per ASTM D 698 for pedestrian and lightly trafficked vehicular areas. Stabilization of the subgrade and/or base material may be necessary with weak or saturated subgrade soils.


Note: Local aggregate base materials typical to those used for highway flexible pavements are recommended, or those conforming to ASTM D 2940. Compaction of aggregate is recommended to not less than 95% Proctor density in accordance with ASTM D 698 is recommended for pedestrian and vehicular areas. Mechanical tampers are recommended for compaction of soil subgrade and aggregate base in areas not accessible to large compaction equipment. Such areas can include that around lamp standards, utility structures, building edges, curbs, tree wells and other protrusions. The recommended base surface tolerance should be ±3/8 in. (±10 mm) over a 10 ft. (3 m) straight edge.


Note: The elevations and surface tolerance of the aggregate base determine the final surface elevations of concrete grids. The installation contractor cannot correct deficiencies in the base surface with additional bedding materials. Therefore, the surface elevations of the base should be checked and accepted by the General Contractor or designated party, with written certification to the paving subcontractor prior to placing bedding materials and concrete grids.

A.  Acceptance of site verification conditions:

     1.  Contractor shall inspect, accept and verify in writing to the grid installation subcontractor that site conditions meet specifications for the following items prior to installation of bedding materials and concrete grid units:

  •  Verify that drainage and subgrade preparation, compacted density and elevations conform to specified requirements.
  •  Verify that geotextiles, if applicable, have been placed according to drawing and specifications.
  •  Verify that base materials, thickness, [compacted density,] surface tolerances and elevations conform to specified requirements.
  •    Provide written density test results for the soil subgrade, base materials to the Owner, Contractor, and grid installation subcontractor.

2.  Do not proceed with installation of bedding materials and concrete grids until [subgrade soil and] base conditions are corrected by the Contractor or designated subcontractor.


   A.         Verify that base is dry, certified by Contractor as meeting material, installation and grade  specifications [and geotextile] are ready to support sand, [edge restraints,] grids and imposed loads.

 B.         Edge Restraint Preparation:

  •    Install edge restraints per the drawings [and manufacturer’s recommendations] [at the indicated elevations.].
  •   Mount directly to finished base. Do not install on bedding sand.
  •  The minimum distance from the outside edge of the base to the spikes shall be equal to the thickness of the base.

 A.         Spread the sand [No. 8 stone] evenly over the compacted, dense-graded base course and screed uniformly to 1/2 to 1 in. (13 to 25 mm). Place sufficient sand [stone] to stay ahead of the laid grids.

 B.        Ensure the grid units are free from foreign materials before installation.

 C.        Lay the grid units on the bedding sand in the pattern(s) shown on the drawings. Maintain straight joint lines.

 D.       Joints between the grids shall not exceed [3/16 in. (5 mm)].

 E.         Fill gaps at the edges of the paved area with cut grids or edge units.

F.           Cut grids to be placed along the edge with a double-bladed splitter or masonry saw.

G.        Sweep [top soil][No. 8 aggregate] into the joints and openings until full.

H.         Sweep the grid surface clear prior to compacting.

 I.          Compact and seat the grids into the screeded [bedding sand] [No. 8 aggregate] using a low-amplitude, 75-90 Hz plate compactor capable of at least 4,000 lbs. (18 kN) centrifugal compaction force. Use rollers or a rubber or neoprene pad between the compactor and grids to prevent cracking or chipping. Do not compact within 6 ft (2 m) of the unrestrained edges of the grid units.

 J.         All work to within 6 ft (2 m) of the laying face must be left fully compacted at the completion of each day.

 K.         [Broadcast grass seed at the rate recommended by seed source.][Place sod plugs into openings.] [Add topsoil to the surface to cover the seeds.]

 L.         Remove excess [topsoil][No. 8 aggregate] on surface when the job is complete.

M.        [Distribute straw covering to protect germinating grass seed [sod]. Water entire area. Do not  traffic pavement for [30] days.] if seeded.


 A.         After removal of excess top soil/aggregate, check final elevations for conformance to the drawings. Allow 1/8 to 1/4 in. (3 to 6 mm) above specified surface elevations to compensate for minor settlement.

 B.         The final surface tolerance from grade elevations shall not deviate more than ±3/8 in. (10 mm) over a 10 ft (3 m) straightedge.

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

 D.        Lippage: No greater than 1/8 in. (3 mm) difference in height between adjacent grid units.


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