This page deals mainly with residential rodent control, for commercial rodent control please follow this link
Rodents experience 'explosive reproduction'. One pair of rodents will have 6 to 10 sets of 6 to 10 young per year, with their offspring being capable of also having babies, in about two months. A few minutes with a pencil and a calculator and you can see that can equal hundreds if not thousands of rodents, per year... for each and every pair of rodents.
All those teeming masses need food and shelter. It is very much a matter of life and death. No food = starvation, no home = being food for some crafty cat, some eagle eyed raptor bird, or some lucky ratter dog.
Every night when rodents go out to feed they scour neighborhoods for food sources, safety areas they can hide from predators in, and potential nesting sites.
All they need is a gap of a quarter inch for a mouse or a half inch for rat. They are quite happy to make smaller gaps bigger - and they have the teeth to back that up.
And two things to keep in mind: if the rodents you have, have access outside your home to an exterior, preferred food source, you may not even be able to trap or bait them. They may not want what you put out. And if rodents have been in your home? The smells they leave behind, are like large flashing neon lights that scream: HOME. Homes which have been infested are much more likely to be reinfested.
A professional inspection will look all aspects of your home. It will look at your siding systems to see how well they fit your home and how will they fit into other systems, and for anything that passes through them. It will look at your foundations and slabs, and how they connect to each other and the wood framing of your structure, it will look at doorways and entrances, vents and access panels, it will look at your sub area for tunnels, utility pass throughs and irregularities that could not be seen from the exterior. It should look at attics, basements, garages, and plumbing areas.
Most of all. a professional inspection is done by professionals. Only experience, good training, and determination yield professional results. It is well worth whatever you pay for good quality work.
Every home should have a pest and rodent inspection every 3 or so years to make sure the home remains free of pests and conducive conditions. It's green and it will save you money over the life of your home.
Expanding foam is candy for rodents, not only is it soft and easy to chew - it is actually attractive to them and they enjoy chewing it, an yet we see homeowners, contractors, and even other supposed pest control professionals use it all the time to stop rodent access.
Using the right materials to keep rodents out and understanding the tolerances involved in doing rodent exclusion is vital. We use metal flashing - not aluminum, galvanized metal hardware cloth, and concrete patch or mortar. You even have to be careful where you use steel wool, because it can rust and becomes worthless, if used in areas of high moisture.
We are now seeing homes that have paid for the 'entire crawlspace cleanup' and 'full insulation replacement' procedures multiple times - and they still have rodents. (And those procedures cost thousands of dollars each time.)
Sometimes the wrong materials are used, but sometimes they just aren't used properly. We commonly see even experienced contractors misjudge how tight sub area access doors need to be. Exclusion is a specialised skill, like being a finish carpenter. It takes training, and years of experience to get good at it.