Rodent Proofing

For Pest Assassin’s technicians is a standard upon survey/inspection to look for potential entry points and eliminate as many as possible. This is the way for a permanent rodent problem solution.


…Rats and mice cause serious damage to all kinds of structures if they are allowed access to them. Damage by rodents has been documented in homes, apartments, hotels, office complexes, retail businesses, manufacturing facilities, food processing and warehouse facilities, public utility operations (especially power and electronic media operations), farm and feed storage buildings, and other structures.

In urban settings, rodents most often cause damage to older, inner-city buildings and utilities in poor repair. New housing developments may experience commensal rodent problems, but problems are more noticeable in neighbourhoods 10 to 12 years of age or older. Ornamental plantings, accumulation of refuse, woodpiles, and other such sources of harbourage and food are more quickly invaded and occupied by rodents when adjacent to an established rodent habitat.

Commensal rodents consume and contaminate human and livestock feed. One rat can eat about 1/2 pound (227 g) of feed per week, and will contaminate and waste perhaps 10 times that amount.

Rodents destroy insulation, electrical wiring, plumbing, and other structural components of buildings. Insulation damage alone may amount to a loss of several thousand pounds in only a few years. Energy loss from damaged buildings results in added annual costs. Rodent-induced fires from damaged electrical wiring or nest building in electrical panels cause loss of property and threaten human safety.

Rodents also serve as vectors or reservoirs of a variety of diseases, such as salmonellosis, leptospirosis, and murine typhus that are transmittable to humans. Additionally, they may be sources of swine dysentery, brucellosis, sarcoptic mange, and tuberculosis, all of which affect livestock or pets.

The most effective means of limiting rodent damage is rodent-proof construction. Rodent proofing is a good investment although it involves multiple factors to consider. Fist of them is the ability of rodents:

Both rats and mice can:

  • run along or climb electrical wires, pipes, fences, poles, ropes, cables, vines, shrubs, and trees to gain entry to a building
  • climb almost any rough vertical surface, such as wood, brick, concrete, weathered sheet metal, and many plastic products
  • crawl horizontally along or through pipes, augers, conveyors, conduit, and underground utility and communications lines
  • gnaw through a wide variety of materials, including lead and aluminium sheeting, window screens, wood, rubber, vinyl, fiberglass, plastic, and low-quality concrete or concrete block.

Rats can:

  • crawl through or under any opening higher or wider than 1/2 inch (1.3 cm) (Fig 3);
  • climb the outside of vertical pipes and conduits up to 3 inches (7.6 cm) in diameter; climb the outside of larger pipes attached to buildings by bracing themselves between the wall and the pipe; climb the inside of vertical pipes, wall voids, or earthquake safety seams and joints between 1 1/2 and 4 inches (3.8 and 10.2 cm) in diameter;
  • jump from a flat surface up to 36 inches (91 cm) vertically and as far as 48 inches horizontally;
  • drop 50 feet (15 m) without being seriously injured;
  • burrow straight down into the ground for at least 36 inches (91 cm);
  • reach as high or wide as 13 inches (33 cm);
  • swim as far as 1/2 mile (800 m) in open water, dive through water traps in plumbing, and travel in sewer lines against a substantial water current. In areas where high rat populations exist, it is common for both roof rats and Norway rats to enter buildings through toilets and uncovered drains.

House mice can:

  • enter openings larger than 1/4 inch (0.6 cm);
  • jump as high as 18 inches (46 cm) from a floor onto an elevated surface;
  • travel considerable distances crawling upside-down along screen wire;
  • survive and reproduce at a temperature of 24oF (-4oC) if adequate food and nesting material are available.

Some of the most common entry points for rodents:

  • utility pipes, electrical conduit (often at meters or circuit breaker panels), water and gas lines, and communication cables generally have large openings that permit entry of mice and rats. Once rodents have entered walls, they generally have ready access to much of a building via holes for utility pipes and wires in the framing, and via overhead suspended ceilings or other types of construction adjacent to utility enclosures.
  • poorly sealed heating and air conditioning ducts; roof and wall vents installed without strong, well-attached hardware cloth screening; roof and wall joints and edges without properly installed metal flashing; and doors hung unevenly or too high, or lined with unprotected soft rubber weather stripping. Doors should fit tightly, the distance between the bottom of the door and the threshold not exceeding 1/4 inch (0.6 cm). In some instances, it is possible to build up the threshold rather than modify the door. Install flashing or a metal channel on the lower edge of doors, particularly softwood doors
  • Chimneys should be checked for properly installed flashing or for missing mortar
  • Rats occasionally enter buildings through toilet traps in inner-city areas with rat-infested sewer systems. In such cases, tracks and water may be found on the rim of toilet bowls. Both roof and Norway rats have been known to enter structures via the sewage system. This route usually occurs in older (20 years or more) established areas with poorly maintained sewer systems. If the sewer system is known to be rat-infested, a “Rat Guard” one way flap valve may be placed in the main drain outlet that allows waste water to exit into main sewer but do not allow rat enter into the drain system of the property. Drain should be checked for defects that could allow rodent entry. If rodding eye is exposed rats can enter through it, rodding eye cap should be in place.
  • Mice often enter under entry doors, through holes beside water pipes and electrical conduit, and through the cold air return ducts on forced air furnaces, especially those located in outside cabinets or garages.
  • Mice and rats often find easy access to garage areas through open doors or under and beside poor-fitting garage doors. Once in the garage, they may gain entry into the main structure along electrical lines, pipes, poorly sealed fire wall sheathing, or around furnace ducts, hot water heaters, or laundry drains. Mechanical door-closing devices save time and help overcome human negligence.
  • If rodents are able to reach the attic, they may travel from room to room or unit to unit through openings for pipes, ducts, and wiring. Common attics, basements, or raised foundations in condominiums and apartments are a frequent source of rodent infestation.
  • Gaps or flaws along building exteriors where the wall framing or siding meets the foundation provide easy entry for rodents. Such openings can be prevented by well-formed and finished concrete work and installation of tight wall framing and siding, or installing metal screed-type flashing between the siding and the foundation. Use of rodent-proof exterior surface materials such as concrete, plaster, or metal sheeting is also effective if properly installed so that all ribs or corrugations are closed.


  • Rodents can gain entry into buildings with piers or shallow foundation walls by burrowing beneath the floor or foundation. To prevent rat entry by this route, extend foundation walls below ground at least 36 inches (91 cm).



  • When rats or mice are present in a building, attention must be given to interior as well as exterior rodent-proofing to remove all sources of shelter. Concrete floors are preferred to wooden floors. An attempt should be made to seal off rodents by closing all gaps bigger than 5 mm.




Recommended materials for proofing:

Neoprene seals, spray-in-place foam, and similar products commonly used to close openings are not rodent-proof.


Rodent proof materials are:

Concrete: Minimum thickness of 2 inches (5.1cm) if reinforced, or 3 3/4 inches (9.5 cm) if not reinforced.

Galvanized sheet metal: 24 gauge or heavier for wall or pipe barriers; 22 gauge or heavier for kick plates or door edging. Perforated or expanded sheet metal grills should be 14 gauge.

Brick: 3 3/4 inches (9.5 cm) thick with joints filled with mortar.


Hardware cloth (wire mesh): Woven, 19-gauge, 1/2- x 1/2-inch (1.3- x 1.3-cm) mesh to exclude rats; 24-gauge, 1/4- x 1/4-inch (0.6- x 0.6-cm) mesh to exclude mice.


Aluminium: 22 gauge for frames and flashing; 18 gauge for kick plates and guards…


Rodent Proofing image
Rodent Proofing