I am looking for natural ways to get rid of vermin in house walls.
Hi @Debbie, welcome to the community.
The best way to get rid of vermin from within the walls of a house it to find the place they are entering and seal it off with wire/mesh which can’t be chewed by vermin such as mice or rats.
The other thing to do is to ensure that trees/shrubs are cut back so that they don’t overhang roofing/guttering. It is best that they are cut back a metre or more to prevent rodents jumping onto the roof and entering by gaps in flashing, roofing materials etc. Also remove anything which allows vermin to climb onto the roof.
Unfortunately using baits there is a risk that the rodents may be within the wall cavity when they die, potentially causing ‘leakages’ which can damage gyprock, pungent smells and attracting other vermin when the body decomposes (maggots, flies and ants). It is also a temporary solution as once the baits are gone, others will most likely move in.
When sealing off, it is best to restrict one access to the wall cavity and when you know the vermin has departed, then seal it up to prevent any vermin re-entering.
Some good pest controller can do a thorough inspection and seal off entry points for you, if it is impracticable for a DIY.