Published October 2025
QUESTION:
Is it acceptable to construct standard interlocking concrete
pavers (ICP) with sand-filled joints on an open-graded
aggregate (OGA) base or bedding?
ANSWER:
This construction method combines a base/bedding from a
permeable interlocking concrete pavement with a surface
layer of standard sand-set interlocking concrete pavement.
Standard sand-set pavers over dense graded aggregate base
with a concrete sand bedding are the recommended assembly
for most ICP applications. Alternatively, standard sand-set
pavers on an open graded aggregate base/bedding may be
appropriate with specific limitations. This pavement system has
the potential to reduce frost heave during winter and minimize
delays caused by wet or cold weather during construction.
However, to achieve these benefits, it is essential to follow
the best practices for both pavement systems and carefully
consider the recommendations outlined below.
To evaluate this approach, the ICPI Foundation funded a
three-year study, “Open Graded Drainage Position Statement
Research,” conducted by Englobe which concluded in 2025. The
final report is available on the Concrete Masonry & Hardscapes
Association (CMHA) website at masonryandhardscapes.org.
Standard ICP on an OGA base systems use materials
and construction techniques from standard interlocking
concrete pavements and permeable interlocking concrete
pavements. Please refer to CMHA’s technical resources for the
recommendations related to these systems in addition to the
recommendations below.
DESIGN RECOMMENDATIONS
- This method of construction is only for Residential
Pedestrian Projects: patios, pool decks, sidewalks,
and walkways. It is not for any commercial or vehicular
applications. - Geotextile is installed along the bottom and sides of the
excavation to stop surrounding soil from migrating into the
open-graded aggregate base. - Jointing Material: Use ASTM C144 mason sand or polymeric
sand. ASTM C33 concrete sand may be used, however, it
is more difficult to work into the joints compared to other
recommended materials. - Underdrains should be included where subgrade soils are
not highly permeable to prevent water from collecting in the
base and saturating the subgrade. - Edge restraints must provide a stable edge that will resist
lateral spreading of the concrete pavers. Edge restraints
used for PICP applications are appropriate.
CONSTRUCTION RECOMMENDATIONS
- Open graded aggregates must be compacted, to prevent
future settlement and proper load distribution. Compaction
can be confirmed by using a lightweight deflectometer and
achieving an average maximum deflection of 0.6 mm.
MAINTENANCE RECOMMENDATIONS
- Joint sand will migrate into the open graded aggregates
below. It is important to monitor sand loss and replenish
when the loss is greater than 1/2 in. (12 mm). - Stabilized joint sand should be used with caution. While
joints may appear full after installation, sand loss from
below can leave only a thin surface crust. Over time, the
binder will break down, leading to increased sand loss.
Monitor joint sand loss and replenish as per manufacturers
recommendations. - Check for lateral shifting, heaving, rutting, or settlement of
the pavement surface and repair as needed.
While open-graded aggregate base systems can provide
benefits such as increased frost heave resistance and fewer
weather-related construction delays when used beneath
standard interlocking concrete pavers, they may not be
appropriate for all projects.
Optimal performance of interlocking concrete pavement relies
on thorough site evaluation, appropriate material selection,
proper construction techniques, and regular maintenance.
Contractors should carefully assess soil conditions, drainage
needs, and anticipated loading before selecting this system.
Inadequate evaluation or unsuitable design choices, particularly
in high-load applications, can result in premature deterioration.
For best results, it is recommended to use the services
of a qualified CMHA Certified Concrete Paver Installer
and refer to the latest technical resources available at
masonryandhardscapes.org. A careful, site-specific approach
helps ensure the system functions as designed and provides
long-term performance.