Site preparation
Graham (1991a) recommended that toxic
materials be removed, if present at the site,
to prevent potential contamination. The site
should be graded to prevent standing water,
which provides breeding sites for insects
(especially mosquitoes). Storm sewers should
be provided. Many municipalities demand
landscaping for aesthetic reasons; however,
shrubbery should be at least 10 m from
buildings to eliminate protection for pests
such as birds, rodents, and insects. Grass
should not be present within 1 m of building
walls so that a pea gravel strip 7.5- to 10-cm
deep can be laid over polyethylene or the
equivalent to discourage rodent entry.
Building construction considerations
Walls
The foundation and walls of a food pro-
cessing or foodservice facility should be
impervious to moisture, easily cleaned, and
constructed to prevent rodent entry. Gra-
ham (1991b) recommended that a slab floor
contain footers constructed with a rodent
flange 60 cm below grade, extending 30 cm
out at right angles to the foundation to pre-
vent rats from burrowing under the floor
slab and gnawing their way into the build-
ing. If a basement or cellar is planned, the
floor should be tied directly to the solid wall
foundation to create a solid box as a pest
barrier.
The most appropriate walls are poured
concrete, troweled smooth to a maximum of
nine holes per square meter, none of which
exceeds 3 mm. Poured concrete is more
expensive and requires on-site construction
of forms and finishing, but it does not have
seams that require the caulking that is
needed for precast or tilt-up construction.
An alternative material is notched beams,
notched precast wall panels, and double-tee
precast roof panels. This technique involves
precasting the wall panels and the roof sup-
port beams, complete with notches large
enough to accommodate the precast double
tees of the roof panels. By fitting inside the
notch, dust-collecting flat surfaces on top of
the beams or wall panels are eliminated.
Caulking the spaces around the double tees
creates a hygienic structure. Caution about
precast, tilt-up, and concrete block construc-
tion is important. Use of a parting agent to
enhance the removal of the panel or block
from the form necessitates that the agent be
tested to ensure compatibility with any wall
covering (i.e., paint and epoxy). Incompati-
bility results in paint peeling.
If concrete block wall construction is
incorporated, it must be a high-density type.
Less porous material reduces moisture
absorption and reduces microbial growth.
An effective sealer can close pores to
improve hygienic design. Graham (1991b)
recommended that when concrete block is
laid, the first course should have the center
core filled with mortar to provide an effec-
tive seal against insects entering through the
joint created at the junction with the founda-
tion. Walls should be covered at the floor, to
a minimum radius of 2.5 cm. Concrete
blocks should be capped off to prevent
access by rodents and insects.
Corrugated metal siding is not recom-
mended because it is not reliable in stopping
the entry of insects and rodents, and because
this material is damaged easily. If corrugated
metal is incorporated, the outside corruga-
tion must be blocked and caulked at the top
and at the foundation to discourage pest
entry. Wall penetration for access by utilities
should be sealed the same day that this oper-
ation is performed to reduce pest invasion.
Wet processing areas should have glazed
ceramic tile or baked-on enamel-insulated