The catio safety checklist, explained

This guide explains the reasoning behind each section of our interactive catio safety checklist. It is general guidance — not an inspection, not a certification, and not a substitute for local rules or professional advice where a design needs it.

Enclosure

A catio must be enclosed on every side, including the top: cats climb mesh easily. Mesh openings need to be small enough for your smallest cat — kittens get through gaps that look impossible. Use welded wire, fixed closely and evenly along every edge, and turn in or cover cut ends.

The weak points are the joints: where walls meet the roof, the ground, the house and each other. Look at every corner from a cat's height.

Doors and access

Most escapes happen at doors. Every door should latch on its own, resist a cat's nudge, and ideally close by itself. Escape-prone cats benefit from a vestibule. See doors and latches.

The house

Attached catios share a wall with things that must stay outside the enclosure or accessible:

• Dryer and fuel-burning appliance vents can discharge hot, moist or combustion gases. They must never open into an enclosure.
• Meters, shut-offs and utilities need access for you, emergency services and utility workers.
• Emergency-exit windows from bedrooms must not be blocked.
• Wall fixings belong in the wall structure, not siding or trim.

Weather

Cats can overheat. Provide shade at the hottest time of day, shelter from rain and wind, and water that cannot tip over. A mesh roof under heavy snow can sag or fail. See shade and weather.

Ground and predators

On soil or grass, cats and other animals can dig. A mesh skirt laid flat outside the walls, or mesh buried below them, stops this. Anchor the frame so it cannot shift. A solid structure and a full roof keep wildlife out as well as cats in.

Welfare

A catio should be somewhere a cat wants to be: a place to hide, a place to rest out of the sun, several heights, and water. With more than one cat, avoid dead ends where one can trap another. See designing for cat behaviour.

Plants and chemicals

Check every plant within reach against a toxic-plant list such as the ASPCA's, remembering no list is complete. Lilies — true lilies and daylilies — are dangerous to cats and should be kept out entirely. Keep slug pellets, pesticides, fertilisers and treated-wood offcuts out of the catio. See the planting guide.

First use

Check the finished catio before the first visit, supervise early visits, and watch where your cat tests the edges. Re-check latches, mesh and fixings every season and after storms.

How OpenCatio3D uses this

The planner runs these checks on your design as you draw, grades each finding as a blocker, warning, advisory or info, and links its sources on the rules page. A clean result reads "no issue detected by the current rules" — never "safe".

Frequently asked questions

How do I make sure my catio is escape-proof?

Enclose every side and the roof with suitably small welded mesh, close every gap at joints, fit latches cats cannot open, and supervise early use. See escape-proofing a catio.

Can a dryer vent be inside a catio?

No. Dryer and appliance vents should discharge outside the enclosure. Move the catio or have the vent rerouted by a qualified installer.

How often should I inspect a catio?

Before first use, at the start of each season and after storms — plus a quick look at latches and mesh whenever you clean.