Foam and mud are useless. The only thing that does work is hardware cloth 1/4 mesh and mortar.
Other things not to use are foil and window screen. Sheetrock is also a dud.

 

At the farmhouse, they even chew through the wood siding.

 

Thanks for the help guys. Spent some wonderful time up in the attic today -- I've needed to go up there and check my flexible HVAC ducts as I was suspecting the insulation was coming off of them. Well good news on several fronts: ductwork is in great shape, and I could not find ANY sign of rats being up there -- we have mostly blown insulation (about 12" thick), which sticks to you like glue and at least this time I wore coveralls and a dust mask. Inspected the area I heard the noise and I'm wondering if we either have birds or bats nesting under the roof tiles? Everything dry and tight, but I still put an ultrasonic unit up there and zapper trap where I think they would come in - where the Freon lines to the 2 HVAC units go thru the wall - I've had them come in there before and blocked it off, but now there is a nice "hole" there...

Scott: Slab foundation, two stories, stucco (which I hear rats can climb), curved soffit with continuous metal soffit vent all around.

And now I have my tree hugging neighbors in a lather because I warned them of the rat problem and I was using non-second-kill bait... hooo boy, sometimes folks just need to go back to suburbia...

We'll see if I hear anything tonight...

Scott

 

 

Having recently lived or owned several houses where EVERYTHING fell off the flex duct but the plastic duct itself, I was worried ours at almost 20 years old would be suffering the same. The flex stuff is ONLY to make it easy for the hvac guy to install it, dust his hands, and walk away. Hard pipe, well, is harder to install, and that's why the craft of sheetmetal worker has fallen to dismay... Wish I had nothin' but insulated sheet metal plenums and ducts...
Thanks,
Scott

 

Can't tell you the number of DEAD MICE I've pulled out of F-250, F-350 plenums, HEADLINERS (yes those little rodents luv climbing and nesting up there), door panels, the WORKS. (half the trucks on the road have dead rodents and the owners don't even realize it)....................the inspection cameras work great locating dead carcasses in the plenum. None of the so-called repellants (dryer sheets, peppermint, moth *****, etc) work so you're back to sealing up the cab --- you'd be surprised the number of openings in a typical F-Series regular, extended or crew cab...............I use combinations of seam sealers, expanding foams and have even placed screens inside the vents found between the cab body and the bed...................

At my farm I rely on the black snakes to keep things in check --- they don't get the #7-#9 loads the copperheads, cotton mouths, etc get............................