Risk of rats in construction
The brown rat, rattus norvegicus, is a UK rodent that is closely associated with human activity. Primary habitats include sewers, canals and rivers; however, they are often found in derelict sites or near readily accessible food sources. Rats can pose a risk to construction workers becuase of the frequency with which they may be in close proximity.
Construction work on greenfield sites can disturb rodent populations, as it can on brownfield sites, for example, when undertaking roadworks or demolishing or renovating old buildings. Construction sites with material storage, temporary offices and worker facilities, can become ideal harbourages for rodents.
Minimising the impact of rodents during construction requires that site managers recognise key signs of activity and that this is addressed quickly to prevent it from becoming a hazard.
Key signs of rat activity include:
- Chewed electrical cables, rubber pipework or pipe insulation.
- Rat droppings, usually around 20 mm long and found in groups.
- Walls with smudge marks or hairs caught on low-level brickwork.
- Scratching or scurrying noises in walls and above ceilings.
- Nests and piled-nest materials.
Surveyors should also look out for these key signs when carrying out a pre-assessment of likely hazards on sites and potential sites.
The primary health hazard posed by rats is Weil’s disease, a serious form of leptospirosis caused by exposure to rat’s urine containing the bacterium, through cuts, scratches and abrasions, and through the lining of the mouth, throat and eyes.
Symptoms are typically similar to flu at the outset – muscle cramps, nausea, headaches – but can cause jaundice, kidney failure, meningitis, and in some cases can be fatal. Other diseases that rats can transmit to humans include:
- Rat-bite fever.
It is possible to become infected even when rats are no longer present, and so workers must be cautious working in any areas with a high quantity of water or in derelict buildings.
 Protecting against infection
There are several steps that can take to protect against infection:
- Ensuring that cuts, grazes or abrasions are covered with waterproof dressings.
- Using suitable safety gloves.
- Washing cuts with soap and running water before covering with dressings.
- Washing hands before eating, drinking or smoking, and avoiding hand-to-mouth contact.
- Avoiding cornering rats as they can jump.
- Avoiding touching a dead rat with unprotected hands.
- Seeking medical attention as soon as possible if symptoms of infection are experienced.
 Structural damage
Rodents can also cause significant structural damage. They can undermine a building’s fabric and can damage drainage by burrowing between joints in the surrounding earth and behind brick sewers. They may cause flooding by damaging pipework, and can create fire hazards by damaging electrical wiring.
Preventive measures can include; placing fine mesh over air bricks to prevent rodent entry, closing off voids around ducts and other penetrations through the building fabric, properly capping drains, installing hinged plates in drains and sewers and so on.
 Related articles on Designing Buildings Wiki
- Construction site inspection.
- Dry rot fungus.
- First aider.
- Hazardous substances.
- Health and safety.
- Japanese knotweed.
- Mitie - drone pest control inspection.
- Personal protective equipment.
- Site surveys.
- The Personal Protective Equipment at Work Regulations 1992.
- Woodworm and spiders.
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