Keeping rats out of foundation wall penetrations

[WWilts]

Concrete to plug the openings where drains / ducts pass through external walls?

Or are there better options?

[PeterW]

Drains have to have a lintel over and be flexible to allow for movement. 
 

Why would a rat dig in a specific area to get through a gap underground ..?? And do you have a current rat issue ..??

[DragsterDriver]

Steel wool.

[Onoff]

Stainless steel "wool" pan scourers from Wilko for example. Jam in and foam in place. In my experience everything from birds to social bees and wasps will have a go at the foam potentially, I've seen it here multiple times. They just seem to sense a nice habitable cavity behind. Best is to then render over the foam.

Edited September 2, 2021 by Onoff