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About

A catio sized to your space

Most catio plans come in a few fixed sizes, and your window, wall or patio is never one of them. The Catio Planner starts from your space: you set the size, it frames a catio that fits, checks it for your cats and lists what to buy.

How it works

  1. 1

    You set the space

    A window box, a lean-to against the house or a freestanding catio, to the inch, and how many cats use it at once.

  2. 2

    It checks it for cats

    Mesh, gaps, floor space and height per cat, shelves, shade and plants, each against a published rule.

  3. 3

    It frames the catio

    2x4 walls stud by stud, the roof with its fall and purlins, the door or hatch, the mesh in bands that match the rolls.

  4. 4

    It counts the materials

    Lumber packed onto standard boards, mesh by the roll, roof panels and every fastener, with shelf prices.

The method

The welfare rules come from humane societies, shelter veterinarians and feline guidelines: the Association of Shelter Veterinarians' standards of care, the AAHA and AAFP feline guidelines, Humane World for Animals, Best Friends, the ASPCA, and Animal Welfare Victoria, the Australian state agency whose cat enclosure pages give the clearest numbers we found. The building rules come from the model code (IRC 2021) and the makers' guides. Each is cited with its year and the date we read it.

Green meets our default. Amber sits below it but within what a source accepts. Red is outside what a source accepts or what we draw safely, and a red rule we cannot draw around stops the plan from being sold until you change the design.

No US source we read gives a number for the largest gap a cat can slip through, so 1 inch is our own default, said as such. The roof framing is sized by span math for the snow load you pick; that is a check, not an engineer's review.

What it is not

The Catio Planner is a planning aid. It is not veterinary advice, it cannot see your wall, your site or your local rules, and it is not a substitute for your building department. Check the plan against your local rules before you build, and have a builder confirm anything fastened to your house.

The designer and the free designs cost nothing and need no account. What pays for them is the builder's plan: a PDF for the exact catio you design, with every wall framed, every cut listed and a step-by-step build, for $29 once. If our plan has an error, we fix it or refund you. The site carries no advertising, and no item is in a plan because someone pays us for it.

Who runs it

The Catio Planner is an independent project operated by Westernmost LLC, 30 N Gould St Ste R, Sheridan, WY 82801, USA. If you find a mistake in a rule or a number, please tell us: a fix to the engine fixes every catio at once.

Sources

Read on or before October 13, 2026.

Shown for comparison only, never as proof:

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