You build a catio with a frame of timber or aluminium, sturdy welded wire mesh with a mesh size of no more than 2.5 cm, and an anchor to the wall or the ground.
Reckon on a day’s work and 150 to 400 euros in materials for a small run against the house. A catio against the rear wall is almost always permit-free, as long as you stay under 3 metres tall and within the rules for your plot.
Most important rule up front: never use chicken wire. It is too weak. A determined cat pushes straight through it or gets a paw caught.
Below I explain everything. Types, sizes, materials, the step-by-step plan and the mistakes I see people make time and again.
What exactly is a catio?
A catio is a cat enclosure: a fenced outdoor space where your cat can safely go outside without wandering off or ending up under a car.
The word is a blend of “cat” and “patio”. You also hear cat run, cat veranda or outdoor run.
The idea is simple. Your cat gets fresh air, sun, birds to watch and room to climb. You stop worrying about traffic, turf wars with other cats, or a cat that never comes home.
What types of catio are there?
There are four main forms. Which one suits you depends on your house, your garden and how much space your cat gets.
| Type | Where | For whom |
|---|---|---|
| Window catio | On the outside of a window | Small, flat, rental |
| Balcony catio | On the balcony, meshed all around | Flat without a garden |
| Lean-to against the wall | Against the rear or side wall, with a cat flap | Most gardens, most practical |
| Free-standing | Loose in the garden, with a tunnel or flap | Big garden, several cats |
The lean-to against the wall is by far the most popular. You link it to a window or door with a cat flap, so your cat comes and goes on its own.
The window catio is the cheapest and quickest. A box of roughly 60 by 60 by 100 cm that you fix to the outside wall with sturdy brackets. Ideal if you rent and are not allowed to build.
How big should a catio be per cat?
Reckon on at least 1 to 1.5 square metres of floor area per cat, but go bigger where you can.
Cats live mainly in the vertical. Height matters more than floor area. A narrow, tall catio with three levels of platforms is more interesting to a cat than a flat, wide box.
Practical guidelines:
- Height of at least 1.8 to 2 metres, so you can stand upright inside it and the cat can climb.
- For 1 cat: 1 by 2 metres of ground area is fine.
- For 2 cats: 2 by 2 metres or larger.
- More cats or lots of indoor sitters: as big as your garden and budget allow.
Better a small catio your cat uses every day than a big one that stays half finished because the job got the better of you.
What mesh do you use for a catio?
Use welded wire mesh (aviary mesh) in galvanised or stainless steel with a mesh size of no more than 2.5 cm. This is the single most important material decision you make.
Why it matters this much:
- Chicken wire is too thin and too floppy. A cat pushes through it or catches a claw or paw. Do not use it.
- Large mesh (5 cm) is recommended on some sites so a paw cannot get caught. But a slim head or a young cat slips straight through 5 cm. For a proper catio it is too open.
- Welded wire mesh with a mesh of 1.3 to 2.5 cm is the best compromise. Strong enough that the cat cannot get through, small enough that a head will not fit, and large enough that a paw will not get caught.
Choose a wire thickness of at least 1.5 to 2 mm (often listed as 16 gauge or thicker). Galvanised is fine, stainless steel costs more but never rusts and is handy near the coast.
Fix the mesh with stainless steel staples every 5 to 10 cm and clamp the edges down with a timber batten. That way the cat cannot slip out underneath and nobody cuts themselves on a sharp edge.
What frame and what foundation?
You have three options for the frame.
| Material | Advantage | Drawback |
|---|---|---|
| Pressure-treated timber | Cheap, easy to work | Needs upkeep, has to be screwed down |
| Aluminium profile | Maintenance-free, light, tidy | More expensive, less easy to cut yourself |
| Steel tube / scaffold tube | Very strong, industrial | Heavy, needs connectors |
For most DIYers, pressure-treated softwood of 44 by 68 mm is the logical choice. Affordable and quick to work with a cordless drill.
For the foundation, one rule: keep the timber off the ground.
- On an existing patio or paving: set the frame on adjustable paving pedestals or a joist layer, so it does not sit in the damp.
- On sand or grass: use concrete footings or ground anchors, or pour a small concrete edge. Weigh the base down with paving slabs if needed to stop digging underneath.
- Against the wall: screw the rear posts to the wall with wedge bolts or wall anchors. That makes the whole structure stable straight away.
A catio does not have to be a bunker, but it does have to stand up to a storm and a climbing cat. Anchoring it to the wall or the ground is not a luxury.
Do you need a permit for a catio?
Usually not. A catio against the rear wall almost always counts as permit-free building, provided you stay within the rules.
The main points for permit-free building in the rear garden area:
- No more than 3 metres tall if the lean-to sits against the house (fixed to the wall).
- A free-standing structure may be taller, up to around 3 metres, depending on the rules.
- You cannot build over your whole rear plot: there is a maximum percentage of built-up area.
- At the front, or on a side bordering public space, stricter requirements apply. A permit may well be needed there.
Note: permit-free does not mean rule-free. The building requirements always apply, even without a permit. And your local council may have extra or different rules.
Not sure? Check with your local council or planning office for your specific situation before you start sawing. It takes ten minutes and saves you a lot of hassle.
How does your cat get into the catio?
Through a cat flap in the window, the door or the wall. This is what makes a catio a catio: your cat goes outside on its own and you do nothing.
The options at a glance:
- Cat flap in a door or panel. Easiest. A flap with microchip recognition lets only your cat through and keeps neighbourhood cats out.
- Flap in a window panel. Replace a pane with a panel (plywood or a made-to-measure window infill, for example) with a flap in it. No holes in your wall, ideal for renters.
- Hole in the wall. The tidy, permanent solution for a lean-to. More work, but the nicest result.
- Tunnel. For a free-standing catio, you link it to the house with a mesh tunnel.
Set the flap low enough that your cat can reach it comfortably, and make sure it sits sheltered from the rain on the catio side.
Open or closed roof: which is better?
Choose deliberately. Part waterproof roof and part open or mesh is the best combination.
A fully meshed roof gives plenty of light and air, but then your cat gets wet in the rain and has no shade on a hot day.
A fully closed roof keeps everything dry, but makes the catio dark and warm.
Practical advice:
- Over the shelter corner and the sitting platforms, lay a waterproof sheet, for example clear polycarbonate (light-transmitting and rainproof) or roofing felt on a sloped little roof for the runoff.
- Leave the rest open with mesh, or stretch a shade cloth over it for the summer.
- Always provide a dry, sheltered spot and a spot in the shade. Cats regulate their temperature by moving from sun to shade.
Always lay the roof at a slight fall so rainwater runs off and no puddles sit on the polycarbonate.
How do you stop your cat escaping?
Close the catio off completely, including overhead, and mind the joins. Most escapes do not happen through the mesh but through a gap you overlooked.
Anti-escape checklist:
- Roof fully closed with mesh or sheeting. A cat climbs higher than you think.
- No gaps at the ground. Clamp the mesh right down to the base or dig it in a little.
- Seams and corners tight. Overlap mesh sections by at least a few centimetres and fix them.
- A door with a good bolt that will not blow open on its own. Cats learn to work handles.
- Meet the wall with no holes. Seal the join with the wall using sealant or a batten.
Is your catio free-standing in the garden and you worry a cat might climb over the mesh? An inward-curved overhang of 40 cm at the top of the wall stops even the most athletic climber.
How do you kit out a catio?
Build upwards and provide variety: climbing, hiding, looking out, scratching and greenery.
- Climbing platforms at different heights. Cats want to sit up high and survey the scene.
- Scratching post or scratching board, vertical and horizontal.
- Hiding spot that is closed and sheltered, so your cat can retreat safely.
- Lookout high up by the mesh, with a view of the garden.
- Water in at least two spots, out of the sun.
- Cat-friendly planting for scent and stimulation.
A litter tray in the catio is handy, but put it under a canopy so it stays dry.
Which plants are poisonous to cats?
Avoid lilies, hydrangea, oleander, yew, azalea, ivy and many bulb plants. These are poisonous to very poisonous for cats and have no place in or around a catio.
Lilies are especially dangerous: even a little pollen or leaf can cause kidney failure in a cat.
Safe and fun for cats, on the other hand:
- Cat grass (oat or wheat grass)
- Catnip
- Basil
- Nasturtium
- Violets
Not sure about a plant? Then leave it out. Better a bare corner than a vet on a Sunday.
Step-by-step: how to build a catio in a day
- Measure and draw. Fix the spot, the sizes and where the cat flap goes. Check the permit rules.
- Prepare the base. Lay paving, pedestals or footings so the frame stands dry and level.
- Build the frame. Stand the posts up, connect them with rails, glued or screwed. Screw the back to the wall.
- Fix the mesh. Attach the welded wire mesh with stainless steel staples every 5 to 10 cm and clamp the edges down with battens. Do not forget the roof.
- Make the door and the flap. A solid door with a bolt for you, a cat flap for the cat.
- Lay the roof. Waterproof sheet over the sitting spot, on a fall. The rest open or with a shade cloth.
- Kit it out. Platforms, scratching post, hiding corner, water and safe plants.
- Check for gaps. Go over the whole catio for holes at the ground, corners and wall before your cat goes in.
What does building a catio yourself cost versus ready-made?
Building it yourself is a lot cheaper. A ready-made kit mainly saves you time and worry.
| Option | Price guide | Note |
|---|---|---|
| Window catio yourself | 50 to 120 euros | Small, quick, rental-friendly |
| Lean-to catio yourself (timber + mesh) | 150 to 400 euros | Most chosen, a day’s work |
| Large or free-standing catio yourself | 400 to 900 euros | More material and foundation |
| Aluminium self-build kit | 700 to 2000 euros | Mesh, door and drawing included |
| Fully made to measure | 2000 euros and up | No work, highest price |
Building it yourself with timber is the cheapest route and gives you exactly the size that fits your wall. A kit pays off if you do not want to saw or have no tools.
Common mistakes when building a catio
- Using chicken wire. Too weak. Choose welded wire mesh.
- Mesh too large. At 5 cm a head fits through. Stay under 2.5 cm.
- Not anchoring. A loose catio blows over or slides away. Fix it to the wall or the ground.
- Forgetting to close the roof. Cats climb out. Always close the roof off.
- No shade and no dry spot. A cat wants to shelter from sun and rain.
- Poisonous plants in the catio. Check every plant, leave lilies out entirely.
- Gaps at the ground and wall. Go over everything before your cat goes in.
Frequently asked questions about building a catio
What mesh do you use for a catio?
Welded wire mesh (aviary mesh) in galvanised or stainless steel with a mesh size of no more than 2.5 cm and a wire thickness of 1.5 to 2 mm. Chicken wire is too weak and not suitable.
Do you need a permit for a catio?
Usually not. Against the rear wall a catio is almost always permit-free if you stay under 3 metres and within the plot rules. Check your situation with your local council.
How big should a catio be?
Reckon on at least 1 to 1.5 square metres per cat and a height of 1.8 to 2 metres. Height with climbing platforms matters more to a cat than floor area.
How does my cat get into the catio?
Through a cat flap in a window, door or wall. A flap with microchip recognition lets only your cat through and keeps neighbourhood cats out.
Can a catio go on a balcony too?
Yes. Mesh all around the balcony and close off the top. Mind your tenancy agreement or homeowners’ association rules, and do not just drill into the wall in a rented home.
What does it cost to build a catio yourself?
A small window catio costs 50 to 120 euros, a lean-to against the wall in timber and mesh 150 to 400 euros. An aluminium self-build kit starts around 700 euros.
Get started yourself
A catio is one of those jobs where a good drawing and the right sizes make the difference between a day’s work and a weekend of fiddling.
Want to start with a worked-out building plan, or are you after more projects to smarten up your garden and home? Take a look at Fred’s DIY Plans. There you will find clear drawings and step-by-step guides that let you get going with confidence, even if you have never built anything before.
Measure, saw, stretch the mesh. And then a contented cat that watches birds all day long.