The rat proofing of granaries is of great importance, because of the
abundance of food stored there and the corresponding opportunity
for serious loss. The granary with concrete foundation and floors,
tight-fitting doors, and screened ventilators presents no unusual
problem, except possibly in connection with the elevator pit, which
should be carefully checked against possible means of ingress for rats.
Small wooden and portable granaries should be protected with wire
netting. (Fig. 10.)
Concrete feeding floors, troughs (fig. 11), water tanks, hog wallows,
and similar structures should be constructed with a curtain wall, or
apron, around the outer edge extending 2 feet or more into the ground
(fig. 12) to keep the rats from burrowing underneath the slab. This
also tends to prevent the heaving caused by frost and the uneven
settling of the structure in soft ground.
[Illustration: Figure 10.--Recommended method of rat proofing a
portable granary]