In rat proofing a city building it is well first to look to the
exterior. If the locality is heavily infested with rats, some
are almost certain sooner or later to find their way into the
building however well protected against them it may be. Garbage
and trash usually comprise the bulk of the rats' food supply. A
metal, water-tight garbage can, large enough to contain all garbage
accumulations between collections and having a close-fitting lid (fig
1), is of prime importance and should be required in all cases by city
law.
[Illustration: B2008M
Figure 16.--An accumulation of trash such as this Is almost certain to
attract rats and should be prohibited by law]
Large accumulations of trash usually, contain much waste food (fig.
16) and are certain to attract rats and furnish an ideal breeding
place for them. Furthermore, they are a menace to health and should
not be tolerated under any circumstances. All other rat harbors,
such as wooden floors and sidewalks very near the ground, should be
removed or replaced with concrete, and piles of lumber and various
materials stored out of doors should be removed or elevated 18 or more
inches. Particular care should be taken to see that sheds and other
outbuildings, porches, steps, loading platforms, and similar structures
on the premises are made rat proof, either by the use of concrete, by
elevation, or by keeping them open to the light and easily accessible.
A thorough inspection should next be made of the building itself and
careful note taken of alterations and repairs necessary for a thorough
job of rat proofing. Inspection should begin in the basement. Doors
and windows should fit snugly, particularly doors leading to outside
stairs or elevators, and these should also be provided with automatic
closing devices. Windows and ventilators should be screened or covered
with gratings, the openings not more than half an inch square. Defects
in basement floors should be repaired with concrete, and floor drains
should be fitted with tight covers, (Fig. 17.)
[Illustration: B3341M:B3331M
Figure 17.--A, Broken floor drains provide a ready means for invasion
by rats; B, rat tracks in freshly laid concrete around newly repaired
drain show that before repairs were made the drain was a rat highway]
Side walls should be carefully inspected, and all openings made for
plumbing (fig. 18), electric-wire conduits, areas around windows and
doors, and unpointed joints in masonry walls (frequently left when
the exterior of the wall is hidden from public view by porches or
platforms) should be carefully closed with cement mortar. (Fig. 19.)
[Illustration: B28391:B4391M
Figure 18.--A, Openings around pipes are a common source of rat
infestation; B, situations like this give rats access to otherwise
rat-proof buildings]
Basement ceilings, when accessible to rats, cause much trouble, and
frequently the best remedy is to remove them entirely. In frame
construction spaces between studs in walls opening into basements
also are a common cause of rat infestation of the whole building. The
permanent closing of these spaces with noncombustible material not
only shuts out the rats but also reduces the fire hazard by stopping
the drafts and the rising of heated gases should a fire start in the
basement. This process of blocking spaces between studs and furring
is commonly known as fire stopping and is of such importance that
the building regulations of many cities now require it. Figure 20
illustrates practical methods of rat proofing stud spaces in old
buildings.
[Illustration: B4388M
Figure 19.--Defects in foundations, such as the opening to the right of
the step, are often the cause of rat infestation in old buildings]
All openings between floors and in partitions made for the passage of
pipes and wires and any defects in the wall should be closed with metal
flashing. All dead spaces throughout the building, such as boxed-in
plumbing, spaces behind or beneath built-in cabinets, counters,
shelving, bins, show windows, and many similar places, should be
removed, opened up, or effectively and permanently proofed against rats.
In the Southern States, where the roof rat occurs, similar care must
be taken to make the upper floors and roofs of buildings rat proof, as
this rat is an expert climber and frequently enters buildings by way of
the roof. Doors at the top of stairs and elevators should fit snugly,
and all ventilators, exhaust fans, unused chimney flues, and other
openings should be screened. Broken skylights and openings under eaves
and places where electric wires enter the building should be repaired
or closed.
[Illustration: Figure 20.--Methods of rat proofing stud spaces in old
buildings: A, Construction at outer wall. Open stud spaces are filled
with weak concrete, which is placed by removing the skirting above. If
the work is done a little at a time, the wooden forms can be removed
when the concrete has set, and used again. B, Another method employing
sheet metal secured to sill, joist, and flooring. C, Post and girder in
basement supporting partition with open stud spaces. Sheet metal nailed
to joists and floor and fitted about the stud prevents access to upper
floors]
[Illustration: Figure 21.--A, Typical construction of frame building on
wooden girders and posts with Joists more than 2 feet above ground; B,
sheet metal placed as shown serves to prevent the rats from climbing to
a point where they can gnaw through the wood]
Buildings that have neither basements nor continuous masonry
foundations present more difficult rat-proofing problems. The most
effective procedure is to construct a concrete foundation wall between
the existing supports and, after the wall has hardened, remove the
supports, if of wood, and replace them with concrete to make the wall
continuous. Where the cost prohibits following this plan and where
the supporting sill and joists are at least 2 feet above the ground
level, satisfactory rat proofing may be attained by stopping the
spaces between the studs with weak concrete or other material resistant
to rats for a distance of 8 inches above the floor level, or with
galvanized-metal flashing nailed to the joists, plate, and floor. (Fig.
21.) The space beneath the building must be free from all rubbish and
other material that would afford shelter for rats. A continuous masonry
foundation, with screened openings to provide ventilation, presents a
more pleasing appearance.
[Illustration: Figure 22.--A, Concrete curtain, or area wall, designed
for rat-proofing purposes; it does not support the building. B, Plan
of wall where supports are of wood; the concrete is bound to the posts
with wire mesh. C, Plan of masonry support; concrete will adhere to the
masonry if the surface is roughened]
If the clearance between the ground level and the bottom of girders
and joists is less than 2 feet, it may provide a hazardous rat harbor.
One of three things should be done: The building should be elevated on
piers 2 feet above the ground; a concrete foundation should be built
as described above; or a continuous concrete curtain wall should be
constructed under the entire outer wall of the building. (Fig. 22.)
Most new city buildings are now built practically rat proof, or could
be made so with only minor changes in the plans and at small cost. Yet
if certain essential details are not included at the start, endless rat
troubles are likely to ensue. It is therefore highly desirable that
plans for every new building include specifications for rat proofing.
All new buildings in which foodstuffs are to be handled should have
ground floors of concrete or other rat-proof material and concrete or
masonry walls extending at least 2 feet below and 1 foot above the
ground surface. All unnecessary openings in the foundation, walls,
and floors should be permanently closed, and windows and ventilators
should be screened. Stud spaces in frame construction should be stopped
with noncombustible material resistant to rats. New buildings in which
foodstuffs are not to be handled may, if desired, be elevated on piers
or posts to provide a clearance of 2 feet between the ground level and
the bottom of the supporting girders, although the concrete or masonry
wall is more satisfactory.