be available in someareasof the countryand will work.Lightdensity or cinder
blocks should not be usedas theyare porousand insectscan work theirway to
the center of the block.Fumigation may be a problemas well since the fumigant
willwork its wayto the center of the blockand slowly releaseintothe
workspacelongafterthe plant is backin production.
Manyfacilitiesuse other materials, such as insulatedmetal panelsand
corrugatedmetalespecially in pre-engineered buildings.Concretewallscan be
cast in place(tilt up), precast,or formedand poured.Manyconcrete silosare
cast in place usingslip forms.If you intendto paintor apply epoxycoatings to
tilt up walls, remember to matchthe release agentto the paint or coating
material you intend to use. If the twoare not matched according to the
manufacturer's directions,the coating usedmaynot adhereto the concrete.
Precast panelsare doneat a precaster's locationand truckedto the site wherea
crane of similar piece of equipment hoists them in place ontoa poured
foundation or footer. The panelscan and oftenare precastwithan insulated
center surrounded by concrete sealing the insulation into the concrete wall panel.
The jointsof the precast panelswillrequirecaulkingwitha goodcaulking
compoundmadewithan acrylicbaseto retainelasticity. Therewill be some
maintenance of these jointsrequired, as the plant gets older.Precastingwiththe
insulationalreadyin the wall has the advantageof not having to attach insulation
on the innerwallsurface or underan additionalsurfacecovering material for
refrigeratedor otherwisetemperature-controlled facilities. Tilt up concretewalls
are oftenusedwhen thereis enoughspaceto formand pourthe wallpanelsat
the constructionsite. Theseare preferred by some construction companies and
usedwithgreatsuccess. These too can be pouredwithenclosedinsulation.
Pre-engineered metalbuildings are not greatlypreferredmaterials or building
types. These panelsare difficultto keep sealedas theyhavea highrate of
expansion and contraction and can presentcondensationproblems.If the metal
panels are sandwich panelsthey mustbe equipped withsecure and tightend caps
to prevent rodent and insectinfestation. Rodents can penetrate the insulation and
roamfreelyinsidethe walls if end capsare not provided. All paneljointsshould
be caulked witha goodgradeof caulkto preventinsectinfestationinsidethe
panels. Thereare materials on the market that can be sprayedon the interiorof
the panelsto insulateand seal the insulationwitha resinmaterialthat provides a
seamless surfacethat is easilycleanableand resistantto damage.
Whenexteriorwalls are designedrodent proofingcan be incorporatedinto
the design. A verysimple,inexpensivemethodis to install a rodent barrierat the
baseof the wall by installing a barrier of concrete or galvanized metal
(anywhere from16 gaugeto 28 gauge)24 inches(61 cm) downfromgradelevel
extendingout at least 12 inches(30.5cm).Rats burrow at an angleand will not
try to go around this barrier but will abandon the burrowand go somewhereelse.
There will be a needfor wallpenetrationsfor wiring,plumbing, ventilation,
utility pipes, etc. These penetrationsshouldbe made,framed, and sealedthe
same day in orderto prevent innerwallinfestationby insects and often by
rodents. Pipe penetrations require sealing with sheet metal or galvanized
136 Handbookof hygiene controlin the foodindustry