Railsidings should be paved with concrete. The contents of rail cars
sometimesexhibit damagewithsubsequentspillagewhen the car dooris opened
if the contents werenot adequately securedat timeof loading.If the rail sidingis
not paved,the spilledmaterial can fall out of the car and is difficultto cleanup.
It thenbecomes an attractant for pests. Concreteis preferred to asphalt as
rodents can chewthroughasphaltto dig tunnelsunderthe plantor sidingarea
and concrete is usuallyeasierto cleanthanasphalt.
7.6 Roofareas
Roofs are oftenignored in sanitary designof a facility.Theycan be a major
source of contaminates,especiallyif theyare constructedof materials that are
not cleanable.For example, a tarpaper gravelroof overa vented processingarea
can becomea trap for standing moisture and product spillsor bits of product
coming fromair exhaust vents. The gravelwill trap moisture, preventingit from
draining away,and thusthe roofbecomes an openinvitationto insects, birds,
and evenrodents, especially if thereis foodmaterial mixedin withthe moisture.
Numerous typesof vegetationranging frombits of grass and weeds to 4 and 5
foot(1.2±1.5 m) treeshave been observedgrowing on gravel-covered roofs.
Gravel tarpapertypesof roof should be usedonlyoverwarehouses or other non-
process areas.Thereare numeroussinglemembrane roofsavailable that are
drainableand cleanable. Imholte(1984)recommendsavoidingwateraccumu-
lations that attractvermin; all flat roofs shouldbe designedwithdownspoutsto
handle rainwater. Equip the downspoutdrains with bullet-nosegratesthat
project upward.He also recommendsthatin regions witha coldclimate,
downspoutsshould be located insidethe building to preventfreezing.Imholte
also recommends all openings throughthe roof be curbed and flashed. The curb
should extend12 inches (0.3 m) or moreabovethe finishedroom.Insulation and
roofing materials should extendup the outside of the curbed sidewalls of the
opening. Do not placeinsulationon the insideof the curbwall,as it is difficult to
clean and frequentlybecomes infested withinsects.
The simplest roof is one that also becomesthe interior ceiling.An example of
a sanitary designfor a roof is the doubletee pocketbeamconstruction technique.
The old methodis to rest the double tee precastroof slabs on pre-cast concrete
beams. Thismethodleft spaces between the underside of the roof cavityand the
top of the beams.A muchmore satisfactory technique is to install concrete
beams withpreformednotchesand prestressedtendonsfor structural strength.
The doubletees are then lowered into the notches,eliminatingthe cavity created
by the older method.The seamsare then filledwithbacker rod (a plasticor foam
filler) and caulkedwithan acrylic-basedcaulkfor elasticity. Theseroof/wall
constructionsystemshaveprovento be successfulin creatinga sanitarycon-
ditionas well as visualappearance. Othersystems call for exposed trusssystems
underthe roofsurface. Thereare numeroustypesof roofingsurfaces ranging
frompitch(tar)and gravelto singlemembrane materials overan insulated
130 Handbookof hygiene controlin the foodindustry