bloody rats!

[RandomGrinch]

Yes.

Bloody critters.
So am I, in my Victorian tereace, the bathroom is in the rear 'extension' of the property.
The joists run across the room meeting with next doors in the party wall.
There were huge gaps around these joists where the rats were entering.
I ripped apart my bathroom to get under the floorboards and block the holes with wire wool and expanding foam.
Also a good spray of a bleach solution helps mask the trails they follow - hopefully dissuading them from attacking the foam.
If anyone on the terrace has a more modern extension, the rats can get up through the cavity walls. Once they are up, they then have free reign of the lofts.

 

[opps]

Good point there mate.
Will have to check. The question is, how did these pests find their way to my ground floor ceiling? The walls are solid btw, with one stud wall.

Sorry, I didn't notice that it was a ground floor ceiling.

The easiest way that I can think of to work out which you have is to look at the poo (if you can).

I assume that your flooring joists run from the middle of the house to the back. If so, if the hole is, for example, 1m from the edge of a party wall, trace it backwards to the outside and see if there are any obvious points of entry.

Flooring joists often have holes drilled into them for pipes and cables. I would only expect those holes to be small enough for a mouse rather than a mouse to travel between them. Mice however are pretty quiet.

 

[Jurassicspark]

Bloody critters.
So am I, in my Victorian tereace, the bathroom is in the rear 'extension' of the property.
The joists run across the room meeting with next doors in the party wall.
There were huge gaps around these joists where the rats were entering.
I ripped apart my bathroom to get under the floorboards and block the holes with wire wool and expanding foam.
Also a good spray of a bleach solution helps mask the trails they follow - hopefully dissuading them from attacking the foam.
If anyone on the terrace has a more modern extension, the rats can get up through the cavity walls. Once they are up, they then have free reign of the lofts.

Interesting...