Thanks so much for all the helpful advice. Replies below...
Oh dear, you have my sympathy they are a right pain when they find a way in. When I lived , in a large terraced house, we had the same problem. We called in the council 'rat catcher' who laid poisoned bait. We were told that they come in through the sewers - and ,in fact ours was pushing up a small drainage cover in our cellar, to gain access.
Traps, don't necessarily work as the rats are quite savvy, and can learn what to avoid, which is why the professionals seem to rely on bait. The only problem with this is that if the rat dies somewhere inaccessible the smell can be pretty rank.
I had a job once, looking for dead rats under floorboards in a National Trust property.. The residents thought they could smell one - though none could be found. They had found some earlier, but I think that once your nasal receptors have been assailed, you seem to be able to smell them everywhere.
Yes, I am trying to avoid using poison so that I don't have to go searching for a dead rat and move all the furniture and pull up the carpets. I've had dead mice before and that is bad enough! I don't have any sewer connections under the house - all are external (back garden). I have no idea where they are coming from. I suspect it's one of three things: 1) From a neighbour, through a hole in a party wall. 2) Through a gap where the mains water and gas come in, 3) They've dug a tunnel in the subfloor.
I'll need to figure this out :-(
As you are in a terraced property there is the possibility they are getting in via your neighbours property, you will usually only get rats where they have access to a food source. Do you or they feed the birds as rats and other vermin love these easy meals replenished on a daily basis,they wont stray far from a reliable food source. Traps and poison work best when they are hungry as they are quite clever little B uggers and wont go near them if they have full bellies.
I suspect you may be right Mark.b, but I can't for the life of me figure out where they are getting food. There is no food available to them from my property, and (very thankfully!) they do not emerge at all into my house - no signs on them at all. If it wasn't for my cat, I wouldn't have even known to check under the floor.
I can only think they are feeding on something from a neighbour's house. I have no idea...
Screw the traps to a board to stop them flipping over. Use peanut butter - the little beggars can't resist it.
Thanks for the tip!!
Telltale signs are greasy black marks along walls and around holes where their runs are.
Young rats can get through a terracotta air brick so it's worth checking them.
If you've only just bought the traps you may have to fettle them to get them to work efficiently. There are often burs on moving parts, release rods and so on that can lead to a rat being caught but not killed. Another good reason to screw or tie the trap to something.
Where possible I'd use bait in a suitable bait box, but tie that to something too, the mice in our loft managed to drag a box onto the loft hatch and it sounded like a herd of elephants clog dancing up there.
Thankfully no signs (greasy marks or droppings) they are in my house above the floorboards - just underneath.
It's entirely possible they have got through terracotta air bricks - mine are intact, but maybe I should add mesh on them??
@Tris how would I use a bait box and trap? put that trap in the bait box you mean?
An old trick is to tie the trap in a sack - it's not so recognisable as a trap.
Good idea! and will make getting rid of them a bit easier if I can just throw the sack out.
Do you have cavity walls? Rats can climb really well and can go up into your roof space or where a pipe enters and is not fully sealed, and down the cavity and then in through the air brick openings on the inner wall or around floor joists. bit more difficult if you are in a terrace as it may not be your house that they are coming in through. I doubt they would travel far from the entrance though so likely to be your direct neighbours houses if its not yours with the hole.
anywhere you suspect as their entry put some leaves/dirt in the way and check if it's moved.
I think I've got mice coming in through a small hole by my door but I don't want to kill them so going to make a one way gate so they can leave but not re-enter (hopefully).
No, my walls are solid, not cavity. I will need to remove a lot (!) of floorboards to see where they are coming from, and I'm worried they will run into my house! eek
I had good success using rat and mouse traps by keeping them baited for three or four days with peanut butter but not setting them. Then I set the traps with more fresh bait and was removing ex-rats several times a day.
good idea!! My traps arrive today, so will leave them unset, with food, to get them used to it.
We had a rat problem when we moved into our current house.
I found the nest was under the rear of the garage, had some petrol for the lawnmower and poured it down and lit a match, I didn't realise there was another access point next to where I was standing, frightened life out of me!
Another one was under the house so petrol was out but the wallpaper stripper was handy which with a 50/50 mix of bleach boiled up and stuck the hose down. Didn't see them again!!
I will have to put something down there to deter them, assuming I can't find and block where they came in from!