Each sealing is a unique situation and rats are very intelligent
   animals. They can fit through a hole the size of a quarter. At
   [1]Affordable Trapping we've been doing this for a long time and
   OTHER trappers have called us on difficult cases they've had
   that we've been able to solve. Age of the home isn't always a
   factor either. Construction techniques, weather, vegetation,
   water, happenstance can lead to an issue but ultimately, it's
   the cleverness and persistence of the animals themselves. They
   want in and they find a way. Well, I'm not selling here. Just
   saying it's not always the obvious that's the problem but the
   nearly invisible and how you handle an issue like these can
   determine whether you've found a long-term solution, or a
   temporary patch that leads to false-confidence and a returning
   or greater issue down the line. == It's not just the material,
   Paul, it's knowing where to seal. Wire mesh is one of the
   materials but we also use others as well. Some materials are not
   good to seal with, and you see them recommended on the Internet
   on DIY pages. Even not all wire mesh is the right wire mesh.
   They can chew right through some gauges of wire mesh or slide
   through it or push it aside. Lots of incorrect information out
   there and even among professional nuisance wildlife removal,
   there's incorrect information. You can seal a whole house and
   *still* miss the entry points and coming in *after* a homeowner
   has tried to do it themselves can sometimes make it more
   difficult as they've obscured important information, making a
   diagnosis more difficult. Of course I can't blame someone for
   wanting to try it themselves first if they like. We're here if
   they have an issue down the road. And yes, it's good to be an
   informed consumer and ask questions. Yet there's also the right
   time to make the phone calls. I could pull a bad tooth with a
   doorknob and a piece of fishing line but sometimes it's best to
   go to the dentist instead. [and compare services with them too
   of course] She is taking the right approach here. Whatever
   company she ends up going with, (of course I hope it's ours and
   that we meet her needs) she's taking the right approach. == I
   suppose my view is biased - often by the time people contact us,
   they're more than ready. It's possible that people have had
   successes at DIY but from my vantage point, I never see DIY
   successes - I only ever see the aftermath of the unsuccessful
   that we then fix for them. In short, a kind of confirmation bias
   but maybe more of a selection bias. I can't know the amount of
   people who don't call/contact us and what their stories of
   success or failure is, just the ones that do. == You'll be
   meeting with Mike - he's got the eagle eyes and knows his stuff.
   I'm good at back-end business stuff but I can't do what he does.
   Apologies for taking up so much of your discussion here and I
   hope you find the solution that works for you smile emoticon ==


References

   Visible links
   1. https://www.facebook.com/Affordable.Trapping/?hc_location=ufi