Building Cat House
When building a catit is good to remember that although most cats are very active and get the exercise that they need by climbing, hunting, playing and exploring especially if they live outdoors. Cats who live indoors can often suffer from being overweight. When your cats live outside they more or less keep themselves entertained. In the case of males the exploring part can be a source of problems unless you have your "tom" neutered. When male cats take off in search of females in heat they are very susceptible to returning home not only injured (and possibly infected) from fights with other males but can also contact feline born diseases from coming into contact with stray or feral cats that have never been vaccinated.
Another problem that wandering males can have is that they often suffer from malnutrition during their female search forays. It is important that if your "unfixed" male is disappearing regularly to make sure he is getting good quality and high in nutrient meals. Most cats typically weigh between 2.5 and 7 kg, with some breeds, such as the Maine Coon exceeding 11.3 kg (25 pounds). There are some cats that have been known to reach up to 23 kg (50 lb), due to excessive overfeeding. This is of course very unhealthy for the cat, and should be prevented through exercise and diet. If you plan to put your cat on any kind of a diet it is always recommended that you first speak with your cat's veterinarian about your plans so that the vet can offer any advice and even do a check up if deemed necessary, as weight gain can be the symptom of more serious problems than just over feeding.
Building a catinside means that you will take on the added responsibility of your cat's exercise and whether it stays fit or not will depend largely on you.