Masonry Magazine April 1993 Page. 31
MATERIALS
Geotextiles are fabrics that are often used to separate
the subgrade from the base material. They may also
be used to stabilize the base material. Geotextiles are
available in a variety of materials and thicknesses.
Geotextiles are typically specified by weight and
permeability. Geotextiles may be woven or non-
woven. The type of geotextile used will depend on
their suitability in brick paving applications. The spec-
ification of geotextiles is beyond the scope of this
Technical Notes. Geotextile manufacturers should be
consulted on the suitability of their product in a partic-
ular brick paving application.
Sheet membranes are often used as bond breaks or
waterproofing membranes. Materials such as building
felt, PVC, polyethylene or other proprietary mem-
branes can be used in brick paving applications. Felt
should conform to ASTM D 226 or D 227. Strength
and thickness of these materials should be such that
they will resist punctures.
Liquid-applied membranes are often used to water-
proof decks and may be used as bond breaks. When
used to waterproof, liquid-applied membranes should
be self-adhered to the base to minimize migration of
water caused by leaks. Application and thickness of
the liquid membranes should follow the manufacturer's
recommendations.
INSTALLATION AND WORKMANSHIP
One factor which has a great impact on the perfor-
mance of brick pavements is workmanship. Proper
preparation and compaction of the base is absolutely
critical. There are numerous ways to install brick
pavements which vary by region. The recommenda-
tions in this Technical Notes are based on experience
and provide a minimum level of workmanship neces-
sary for satisfactory performance.
Subgrade Preparation
One element common to all paving assemblies is the
soil or subgrade. In preparation for the base or sub-
base, the subgrade should be excavated to the proper
elevation, deleterious materials removed, and the sub-
grade compacted. If subsurface drainage is required,
drain pipes should be installed and be properly back-
filled. The entire subgrade should be compacted to 90-
95% maximum density.
Flexible Base Systems
Only mortarless brick paving should be placed over
flexible bases. Generally, flexible bases are the most
economical type of base to install. Proper construction
of the subbase, sand setting bed and brick pavers is
necessary to ensure good performance.
Subbase and Base Preparation
The subbase and
base materials should be spread and compacted in lay-
ers. The thickness of these layers must be consistent
with the capabilities of the compaction equipment.
Heavy compaction equipment such as vibratory rollers
may be necessary when constructing a street with
crushed stone, whereas a plate vibrator may be used
when constructing a sand base for a residential patio.
Each material should be placed and compacted in lay-
ers no greater than 4 in. (100 mm). It is essential that
the intended surface profile of the pavement is formed
by the base so the pavers can be placed on a uniform
thickness of bedding sand.
If a geotextile is used, it should be placed after com-
paction of the subgrade or base. The geotextile should
be placed smooth and be overlapped a minimum of 12
in. (300 mm) at its ends. The geotextile should be
lapped further in conditions such as poor soils. The
geotextile should be placed so that the material entirely
covers the base and extends up the side of the excavat-
ed area to contain the setting bed material. Construc-
tion equipment should be kept off of the geotextile.
Check the geotextile manufacturer's literature for fur-
ther installation recommendations.
Edge restraints should be placed before base installa-
tion if the restraint is anchored below the base. The
edge restraint should be installed after base compaction
if it is intended to be anchored into the base. In the lat-
ter case, the base should extend at least 6 in. (150 mm)
past the end of brick paving above.
Setting Bed Preparation
The setting bed material
should be spread over the base in a uniform thickness.
A screed board is often used to spread the sand. The
setting bed is not meant to and should not be used to
fill in low spots nor its thickness adjusted to bring the
pavement to the correct grade. Any changes in thick-
ness or undulations in the sand will reflect on the pave-
ment surface. To prevent disturbance of the sand it
should not be spread too far in front of the laying face
of the pavers. Prepared setting bed materials left
overnight should be properly protected from distur-
bance and moisture. The moisture content of the sand
during installation should be as uniform as possible,
with the material moist but not saturated. Stockpiled
sand should be kept covered to prevent contamination.
Paver Installation
Pavers should be laid in the de-
sired bond pattern with a % to % in. (2 to 3 mm) aver-
age joint width. The term "handtight" is a misnomer
since sand between the pavers is desired. The joint
width should not exceed in. (6 mm).
String lines or chalk lines may be used to keep the
pattern aligned. Whole pavers should be laid first, fol-
lowed by pavers cut to size. All pavers should be cut
with a masonry saw to produce an accurate, clean,
straight cut. A trial area may be laid out in advance of
work to determine paver positions and minimize the
amount of cutting required.
In pedestrian paving applications, jointing sand may
be swept into the joints. In some pedestrian and all
vehicular paving applications, the brick should be
vibrated into place using a mechanical plate
vibrator/compactor. Compaction of the brick forms a
more stable surface and promotes interlock between the
sand and pavers. If a vibrator is used, the first pass of
the vibrator should be prior to the spreading of jointing
sand to force bedding sand into the joints from below.
On subsequent vibrator passes, jointing sand is spread
across the surface before compaction. Several passes
of the vibrator may be necessary to fill the joints.
Compaction should not occur within 3 ft (0.9 m) of any
unrestrained edge.