The complete catio planning guide
How to plan a catio from scratch — choosing a type and a spot, sizing it, getting cats in and people in, and what to settle before you buy materials.
· 4 min read · OpenCatio3D editorial · general guidance, not veterinary, legal or engineering advice
A catio — a cat patio — gives indoor cats sun, air, smells and things to watch, without the risks of roaming. Good ones look simple, but they are the product of a dozen small decisions made in the right order. This guide walks through them.
1. Decide what the catio is for
Write down, in a sentence, what you want. "Somewhere for one cat to sunbathe at the kitchen window" leads to a very different design from "a place three cats can spend the afternoon while we garden". The answer drives the type, the size and the budget.
Think about:
- How many cats, their ages and how agile they are. A senior cat with stiff joints needs ramps; a young escape artist needs a double door.
- How long they will stay. Short supervised visits need little more than shade and a shelf. Long unsupervised stays need water, shelter, a litter option and very careful escape-proofing.
- Who will clean it, and how often.
2. Choose a type
| Type | Best for | Watch out for |
|---|---|---|
| Window box | One cat, small budgets, rentals | Fixings, egress windows, heat |
| Lean-to | Direct access from the house | Vents and meters on the wall, the wall junction |
| Freestanding | Space, several cats, gardens | Anchoring, digging, getting cats there |
| Tunnel | Linking a window to a catio | Joints and supports along the run |
| Porch or deck | Using what you have | Gaps at the floor, posts and ceiling |
3. Pick the spot
Stand where the catio would go at different times of day. You want some sun and some shade, a view, and shelter from the worst wind. Then look at the wall and ground with a builder's eye:
- What is on the wall? Dryer and appliance vents must never discharge into an enclosure. Gas and electric meters, shut-offs and hose bibs need to stay reachable. Bedroom windows that serve as emergency exits must not be blocked.
- What is underfoot? Soil and grass need a dig-proof skirt. Pavers and concrete need anchoring. An existing deck needs sound boards and framing.
- Who can see it? Neighbours, HOAs and landlords may have opinions — and rules. So may your local building department, depending on size and attachment.
4. Size it
Size follows use. A window box for one cat might be 3 ft wide and 2 ft deep; a walk-in lean-to is commonly 6–10 ft wide. Vertical space matters as much as floor area: cats use height for safety and for the view. If you will walk in to clean, the door and headroom set a minimum height.
Allow for the furniture you want — shelves, a bed, a scratching post, planters — and for cats to pass each other. Our behaviour guide covers layout in detail.
5. Plan the ways in
Two kinds of access matter:
- Cat access from the house: an open window into a window box or tunnel, a cat flap in a door or wall, or a window-mounted cat door kit. Make sure you can close it from inside.
- People access for cleaning, maintenance and retrieving a cat: a human door on larger catios, a hatch on small ones. Every door needs a latch a cat cannot nudge open.
6. Settle the construction
Most DIY catios are a timber frame (2×2, 2×3 or 2×4) with welded wire mesh, and a roof of mesh, clear polycarbonate, corrugated sheet or a mix. See the materials guide and the mesh and roofing guide.
7. Check the design before you buy
Run through the safety checklist: enclosure, doors, the house, weather, ground, welfare and plants. In OpenCatio3D these checks run on your design automatically, with a reason and a fix for each finding.
8. Confirm your measurements
Measure twice: the wall, the window or door the cats will use, the ground slope. Only then buy materials. The cost calculator gives a quick materials range; the planner's build package lists every board, roll and fixing for your actual design.
Frequently asked questions
Do I need planning permission or a permit for a catio?
It depends on where you live, how big and tall the catio is, and whether it attaches to the house. Ask your local building department before you build, and check any HOA covenants or lease terms.
What is the best size for a catio?
There is no single answer. Size it for the number of cats, the time they will spend there and the furniture you want, and use height as well as floor area. If you will walk in, allow for a door and headroom.
Can my cat stay in the catio unsupervised?
Only once you have watched how your cat uses it, tested every door and joint, and provided water, shade and shelter. Many owners keep visits supervised, especially at first.