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Indoor vs Outdoor: The Lifespan Difference

The Harsh Reality of Outdoor Cats

Before installing a cat door for outdoor access, understand the statistics: Outdoor cats live an average of 2-5 years. Indoor cats live 15-20 years. That's not a typo - outdoor access reduces lifespan by 75-90%. Leading causes of death for outdoor cats: hit by cars (most common), attacks by predators (coyotes, dogs, larger cats), poisoning (antifreeze, rat poison, pesticides), disease (FIV, FeLV, rabies, parasites), and fights with other cats (abscesses, infections).

Outdoor cats also devastate local wildlife - house cats kill 1-4 billion birds annually in the U.S. alone, driving some species toward extinction. Many cities now have outdoor cat ordinances requiring cats to be contained on owner's property. Before installing a cat door, seriously consider if the risks outweigh the benefits.

Cat Door Sizing: Bigger Than You Think

Cat doors need to accommodate the cat's full shoulder width and height when walking through in a natural position. Measure your cat's height from floor to shoulder (not top of head), then add 2-3 inches for opening height. Measure shoulder width, then add 2 inches for opening width. Most cats need a minimum 6"W x 7"H opening, with large breeds requiring 8"W x 10"H.

The "step-over" height (distance from ground to bottom of opening) affects accessibility. Low step-over (2-3 inches) is easier for kittens and seniors but allows rodents entry. High step-over (6+ inches) keeps pests out but may be too tall for small/senior cats. Standard is 4-5 inches - a compromise between accessibility and security.

Essential Cat Door Features

4-way locks are non-negotiable: (1) In only - cat enters but can't exit, (2) Out only - cat exits but can't re-enter, (3) Both ways - full access, (4) Locked - no access. This flexibility lets you control access based on time of day (locked at night to keep cat safe indoors) or weather (locked during storms).

Microchip-activated doors ($100-200) read your cat's implanted microchip or RFID collar tag, unlocking only for registered pets. This prevents: neighborhood cats entering your home (eating food, fighting with your cat, spraying), wildlife entry (raccoons, opossums are smart enough to use cat doors), and stray cats seeking shelter. Worth the premium cost if you have multiple cats or neighborhood cat problems.

The Catio Alternative: Best of Both Worlds

A catio (cat patio) provides outdoor enrichment without outdoor danger: enclosed outdoor space (screened porch, custom-built cage, window box) where cats experience fresh air, sun, bird watching, and grass/plants in complete safety. Cat doors connect indoor space to the catio, giving cats controlled outdoor access without roaming risks.

Catios range from simple ($200 DIY window box) to elaborate ($2000+ custom structures). Even a 4'x6' enclosed space provides massive enrichment value. Add cat-safe plants (wheatgrass, catnip, cat thyme), perches at different heights, scratching posts, and toys. The cat gets 90% of outdoor benefits (sensory stimulation, exercise, environmental variety) with zero risk of cars, predators, or disease.

Installation Considerations

Cat doors can be installed in: exterior doors (wood doors easiest - just cut hole and mount frame), walls (requires tunnel extension for thick walls, 8+ inch walls may need custom tunnel), sliding glass doors (panel insert replaces part of door, preserves glass), and windows (similar to sliding door installation). Professional installation costs $100-200 on top of door price.

Weatherproofing is critical for exterior installations. Look for magnetic or brush seals that prevent drafts (uninsulated cat doors can increase heating/cooling costs by 15-20%). Tunnel extensions for thick walls/doors maintain weatherproof seal across entire thickness. In cold climates, consider insulated doors with double flaps to trap air and reduce heat loss.