Most cats are very particular about their toilet habits and will consistently use a litter tray indoors or go in the garden. If they are spraying or urinating in the corner of the room or other odd places around the house, however, it can be worrying as well as unpleasant. It can also be a sign of a medical or stress-related problem, so it’s important you look for any inconspicuous upsets or hidden physical conditions.

Is your cat spraying or urinating indoors?
Spraying and urinating are two very distinct actions. Cats use urine as a scent signal or 'mark' for themselves and other cats. The motivation for scent-marking is very different to that of urination to relieve a full bladder. It is therefore important to establish whether the cat is spraying or urinating, since the potential solutions will vary. To urinate, the cat squats and deposits a volume of urine on a horizontal surface. The cat may then scratch at the area around the urine, although this is not always the case. Common sites for inappropriate urination include carpets, settees, duvets, baths or sinks. To spray urine, the cat stands up, usually making a treading motion with their back feet, while quivering the tail, and a small amount of urine is sprayed backwards onto a vertical surface, such as a wall or corner of a piece of furniture, leaving an obvious scent mark. Common sites for spraying include around doors, windows or cat flaps, curtains, electrical equipment and shopping or rubbish bags. Once it has been ascertained which of the two the cat is doing, you can then take action to try to resolve the behaviour.

How to clean cat urine
Whether a genuine accident or not, once your cat has urinated in a particular spot, it’s important to thoroughly clean that spot to stop it from becoming a habit. Unless the smell is completely removed, your cat’s sensitive nose will be able to pick up any lingering smell of urine, which will serve as a trigger to urinate there again.

The best way to break the habit is to keep the cat away from the area as long as possible, remove any smell that the cat can detect and change the geography of the location by using pieces of furniture to block access. Wash the area with an enzymatic or probiotic cleaning solution and allow it to dry. These products are designed to break down the smells that are associated with urine. Carpet is extremely absorbent, and urine often penetrates the full thickness of the carpet to the flooring underneath, making professional cleaning necessary. If the area is badly soiled over a long period, the carpet may become unsalvageable and it may be necessary to remove it and treat the concrete or floorboards underneath before replacing.

Why has my cat started urinating in the house?

Medical problems
A cat that has started to urinate inappropriately in the house should be promptly taken to the vet for a check-up to make sure there are no medical causes of the behaviour change. 

1. Stress cystitis is a very common cause of incontinence. This may be for a number of reasons. Cystitis is an inflammation of the bladder and is very painful. Cats may start to associate their litter tray with pain and so look for other places to urinate. Cystitis also causes the cat to feel that they need to urinate all the time, so they may simply not make it to the tray or the garden in time. Urinary tract infections are rare in cats, but cystitis caused by chronic stress is very common. This can cause many health issues, some of which are life threatening. You can read all about the signs, causes and treatments of stress cystitis, or feline idiopathic cystitis (FIC), as it’s also known, here.
2. Joint disease/osteoarthritis (OA). Osteoarthritis is a common yet under-diagnosed condition in cats, who are very good at hiding signs of discomfort and pain. Pain in the hips, spine and joints of the legs can make fully squatting to urinate very uncomfortable. Cats with OA may not want to go outside to urinate because of the extra effort. This may be especially noticeable in cold or wet weather. If you don’t already have indoor litter trays, it might solve the problem if you get some for your home. Make sure they are in quiet, secluded places, and always have one more tray than the number of cats you have to avoid conflict and ensure there is always somewhere clean to go. If you do have litter trays, try shallower ones with lower edges, and change to a softer litter to make getting in the tray as comfortable as possible. Talk to your vet about medications to help alleviate the pain.

The pain of both cystitis and OA can prevent cats from squatting fully. This can sometimes make it more difficult to differentiate between urinating and spraying. Medical issues should always be ruled out first, no matter what.

Why have my cats started spraying indoors?
All cats, male or female, neutered or not, can spray. Usually this occurs outdoors as a part of the scent communication system. They also leave scent signals by rubbing their faces against objects to deposit pheromones produced by the facial glands or scratching their nails against objects to deposit pheromones produced by the glands between their toes. Cats leave scent not just to advertise their presence to other cats but to cover the area with their own familiar smell.